Low data throughput on nRF9151DK compared to nRF9160

RE: Low data throughput on nRF9151DK compared to nRF9160

Øyvind — Thu, 11 Sep 2025 12:54:27 GMT

Hi Lucas,

There is naturally some roundtrip delay caused by LTE-M. The way data is sent is currently is not optimal. I’m not that familiar with MQTT, but in the log each MQTT message is used to send a few kBs of data. After each MQTT message, the device waits for acknowledgement before it starts sending the next message. Could more data be sent in each MQTT message, or even the whole payload at once?

That said, we asked for the nRF9160 log to see why it does not suffer from similar delays.

Kind regards,
Øyvind

RE: Low data throughput on nRF9151DK compared to nRF9160

l0cszp — Mon, 01 Sep 2025 12:32:15 GMT

Hello Øyvind,

Thank you for analyzing the trace and for the insightful feedback. It is very helpful to know that the delay seems to be related to waiting for TCP ACKs and server responses.

I will capture the reference log with the nRF9160 under the same test conditions. I expect to have this for you by the end of this week.

Regarding the delays, you mentioned the modem is spending a lot of time waiting. In your experience, is this type of latency typically caused by the cellular network itself? We are testing on the Claro network here in Brazil.

To rule out the server, we have already tested this with both a private and a public MQTT broker and observed similar transmission times, which leads us to suspect the network might be the primary factor.

I look forward to your thoughts and will send the nRF9160 trace as soon as it's ready.

Kind regards,

Lucas

RE: Low data throughput on nRF9151DK compared to nRF9160

Øyvind — Thu, 28 Aug 2025 12:12:19 GMT

Hello again, here is the feedback I got:

now it looks like I expected. There are no obvious problems, but a lot of time is spent waiting for TCP ACKs and MQTT messages from the server, i.e. not transmitting data. Would it be possible for the customer to capture a reference log with nRF9160? It would be helpful to see the difference in a modem log.

Can you please capture one from nRF9160 in the environment?

Thanks!

Kind regards,
Øyvind

RE: Low data throughput on nRF9151DK compared to nRF9160

Øyvind — Wed, 27 Aug 2025 07:29:42 GMT

HI Lucas, no worries, and thanks for providing a new trace. Appreciate the patience!

The important part of the trace is to see activity from reset, in order to analyze the SIM communication, and then the data transfer to determine what is causing the bottleneck. I will forward the modem trace to our team and hope to have some feedback by end of tomorrow.

Kind regards,
Øyvind

RE: Low data throughput on nRF9151DK compared to nRF9160

l0cszp — Tue, 26 Aug 2025 13:35:23 GMT

Hello Øyvind,

Thank you for the detailed feedback and clarification. My apologies for the misunderstanding—I misinterpreted the request and captured the previous logs to show the modem's general connection behavior, not an active data transfer.

To confirm, our application is designed to send data via the modem over an LTE connection.

I have now captured a new trace, this time during an active data transfer. The log covers the entire process of my script sending a 300kB payload, which took approximately two minutes to complete.

The new trace is attached to this reply. Please let me know if this is sufficient. If you still need a longer, 30-minute trace that includes continuous data transfer, I can certainly provide that, but please be aware the log file will be quite large.

Kind regards,

Lucas
devzone.nordicsemi.com/.../trace_2D00_2025_2D00_08_2D00_26T13_2D00_24_2D00_25.085Z.mtrace

RE: Low data throughput on nRF9151DK compared to nRF9160

Øyvind — Tue, 26 Aug 2025 13:01:29 GMT

Hi, our modem team have tried to look into this and provided the following feedback:

the log again does not contain any data transfer. There isn’t even LTE attach in the log, but modem is already attached when the log starts. The log is 30 minutes long, so that matches the description. Also, RRC connection gets only activated once in the log. It happens because of a tracking area update 5 minutes before the log ends and the RRC connection is active only for ~200 ms.

I have assumed that the logs should contain data transfer, because the original issue was data throughput issue with nRF9151, but I have not seen any data transfer in any of the logs. There isn’t any socket RPC messages and RRC connection isn’t active either, so the modem can not be transmitting any data. So, just wondering where the data is actually going.

To verify what my colleague is asking, is the data transfer just over UART or via modem?

Kind regards,
Øyvind

RE: Low data throughput on nRF9151DK compared to nRF9160

l0cszp — Mon, 25 Aug 2025 12:50:20 GMT

Yes, that's correct. This trace was captured using one of the original Claro SIM cards.

My initial thought was that the SIM itself wasn't the root cause, as I had tested with two different cards and both were functioning correctly.

Let me know what you find in the new trace.

RE: Low data throughput on nRF9151DK compared to nRF9160

Øyvind — Mon, 25 Aug 2025 06:17:49 GMT

Thanks for sharing a new modem trace. Glad to hear that SIM issue is resolved. I assume that you are still using the same SIM?

RE: Low data throughput on nRF9151DK compared to nRF9160

l0cszp — Fri, 22 Aug 2025 13:39:17 GMT

Hello Øyvind,

I have captured a new modem trace, making sure to press the reset button on the DK right after starting the trace in the Cellular Monitor to include the full start-up sequence. The trace was run for 30 minutes.

On a positive note, it seems the issue with the SIM card has been resolved. I was able to verify its connectivity and status on our carrier's dashboard before this test.

The new trace file is attached. Please let me know if this provides the necessary information from the start-up.

Kind regards,

Lucas

devzone.nordicsemi.com/.../trace_2D00_2025_2D00_08_2D00_22T13_2D00_04_2D00_49.595Z.mtrace

RE: Low data throughput on nRF9151DK compared to nRF9160

Øyvind — Fri, 22 Aug 2025 10:47:33 GMT

[quote user="l0cszp"]While your team is analyzing the modem trace[/quote]

Finanlly got some more feedback. There seems to be an issue with the SIM but the modem trace was not sufficient. They need to see modem traces from start-up which means that when you start modem trace you need to press reset button on the nRF9151DK. Could you please capture a new trace and assure that reset is pressed after starting modem trace in Cellular Monitor?

Thanks

Kind regards,
Øyvind

RE: Low data throughput on nRF9151DK compared to nRF9160

l0cszp — Thu, 21 Aug 2025 13:22:45 GMT

Hello Øyvind,

Thank you for the follow-up. Here are the answers to your questions:

nRF9160 Modem Trace: We do have an existing product that uses the nRF9160, but I do not have a sample in my lab at the moment. I have contacted our client to request a unit for testing and will provide the modem trace as soon as I receive it.
Other SIM Cards: Currently, we only have access to Claro SIM cards. However, we are in the process of sourcing LTE-M SIMs from other local operators to expand our testing capabilities.
Testing Location: All tests are being performed at our facility in Uberlândia, Minas Gerais, Brazil.

I will keep you updated on my progress with obtaining the nRF9160 sample.

Kind regards,

Lucas

RE: Low data throughput on nRF9151DK compared to nRF9160

l0cszp — Thu, 21 Aug 2025 13:16:19 GMT

Hello Øyvind,

Thank you for conducting these tests and providing the detailed results. The benchmark of transmitting 300 kB over TCP in approximately 20 seconds is a very helpful data point for us.

This translates to an application data rate of around 120 kbps. While this is a significant improvement over what we are currently experiencing, the rate still seems modest given the capabilities of an LTE-M network.

The 41-second script execution time is a very useful reference point for us, as it's likely the most similar to our real-world application. Based on that timing, we calculate the effective data rate to be around 58.5 kbps. As we are designing for maximum power efficiency, we are trying to understand all the factors that contribute to the total transmission time.

From your team's experience, does this data rate seem typical for an application script of this nature? We are curious to know if there are common configurations or best practices we might be overlooking that could help optimize this.

Any insights you could share would be greatly appreciated as we finalize our design. We will also proceed with testing without AT%POWERCLASS=5 as you suggested.

Kind regards,

Lucas

RE: Low data throughput on nRF9151DK compared to nRF9160

Øyvind — Thu, 21 Aug 2025 11:47:10 GMT

Hi Lucas, could you please provide a modem trace from the nRF9160 as well? What SIM do you have access to other than Claro? Where exactly are you testing?

Kind regards,
Øyvind

RE: Low data throughput on nRF9151DK compared to nRF9160

Øyvind — Thu, 21 Aug 2025 06:53:49 GMT

Hello, sorry for the late response. Here is what I got in response regarding the general issue of data transfer. Still waiting for more feedback on the modem trace.

The script was tested, and it appears that the command AT%POWERCLASS=5 may be influencing the results. This command reduces the maximum TX power level to 20 dBm and is only supported from MFW version 2.0.2 onward, meaning it is not available on the 9160.

Without this command, no significant differences were observed between the 9151 and 9160 during testing.

However, when the command was used, some differences were noted. While not a radio specialist, the tester suggested that under certain network conditions, reducing the TX power could lead to increased retransmissions, thereby delaying overall transmission time. Additionally, in poor network environments, lower TX power might actually result in higher overall power consumption compared to operating at a higher TX power level.

Measurements are available for both the script and for a test involving the transmission of 300 kB of data over TCP without any intentional pauses. These measurements were taken under specific local network conditions and may not be representative of other environments.

In the conducted tests:

The script execution time was approximately 41–42 seconds, both with and without the AT%POWERCLASS=5 command.
The pure TCP transmission of 300 kB took around 20 seconds.
UART1 was used via a virtual COM port at 921600 baud.

devzone.nordicsemi.com/.../datamode_2D00_test_2D00_nrf9151_2D00_300kB_2D00_below_2D00_20sec.txt devzone.nordicsemi.com/.../customer_2D00_script_2D00_9151_2D00_no_2D00_powerclass_2D002D00_41seconds.txt devzone.nordicsemi.com/.../customer_2D00_script_2D00_9151_2D00_powerclass_2D00_is_2D00_5_2D002D00_42seconds.txt devzone.nordicsemi.com/.../5635.nrf9151dk_5F00_nrf9151_5F00_ns.overlay

KInd regards,
Øyvind

RE: Low data throughput on nRF9151DK compared to nRF9160

l0cszp — Tue, 19 Aug 2025 13:21:29 GMT

Hello Øyvind,

While your team is analyzing the modem trace, I believe it's important to provide some additional context about our project and the performance issue we are facing.

We are developing a battery-powered sensor solution. A key requirement of the application is to transmit approximately 360kB of data per day over LTE.

Initially, we evaluated the nRF9160 but encountered challenges with its current consumption peaks. We then moved to the nRF9151, which has a more suitable power profile for our needs. However, we're now facing a data throughput issue. Our tests show that transmitting a ~300kB payload over MQTT is taking around 1.5 minutes. This transmission time is significantly longer than we expected for an LTE-M connection and negatively impacts our product's battery life.

To help us determine if our results are typical or if there's a configuration issue on our side, would it be possible for your team to provide a benchmark? Knowing the approximate time it should take to transmit a 300-360kB payload using an nRF9151 on your reference setup would be incredibly valuable.

We are on a tight schedule to finalize the hardware for this project and are very keen on using a Nordic solution. Any guidance you can provide would be greatly appreciated.

Best regards,

Lucas

RE: Low data throughput on nRF9151DK compared to nRF9160

l0cszp — Fri, 15 Aug 2025 09:13:10 GMT

Hi Øyvind,

Thanks for the quick response. The original SIM is from the operator Claro in Brazil.

As you suggested, I've run a new 30-minute trace using a different Claro SIM card to help rule out a SIM failure. The new log file is attached.

Hope this helps.

Best regards,

Lucas
devzone.nordicsemi.com/.../trace_2D00_2025_2D00_08_2D00_15T08_2D00_37_2D00_05.390Z.mtrace

RE: Low data throughput on nRF9151DK compared to nRF9160

Øyvind — Fri, 15 Aug 2025 08:22:50 GMT

Hi Lucas, the modem trace might be a little short, as it did not connect to a network. But there is also indications to the SIM card failing i.e. CME ERROR 13 which according to 3GPP 27.007 ch. 9,2 means SIM/UICC failure. What SIM are you testing with?

Could you redo the modem trace and capture for e.g. 30 minutes? Also, do you have another SIM to test with?

Thanks.

Kind regards,
Øyvind

RE: Low data throughput on nRF9151DK compared to nRF9160

l0cszp — Thu, 14 Aug 2025 14:02:54 GMT

Hello Øyvind,

Thanks for the guidance. As requested, I have attached the modem trace to this reply. The trace was captured for approximately 10 minutes.

Please let me know if you need anything else from my side.

Kind regards,

Lucas

devzone.nordicsemi.com/.../trace_2D00_2025_2D00_08_2D00_14T13_2D00_49_2D00_03.928Z.mtrace

RE: Low data throughput on nRF9151DK compared to nRF9160

Øyvind — Thu, 14 Aug 2025 09:13:30 GMT

Hey Lucas, thanks for reaching out to me and making me aware of this ticket.

I have not been able to read through the whole ticket yet, but have forwarded your last comments/logs. I see that you have not provided a modem trace yet, can you please do so? This can be collected through RTT as well if needed. Modem traces provide more information on what is going on in the modem itself, which could give a better understanding of what is failing on your side.

Let me know if I can assist with the modem trace while we wait for comments on your last comment.

Kind regards,
Øyvind

RE: Low data throughput on nRF9151DK compared to nRF9160

l0cszp — Mon, 11 Aug 2025 19:42:51 GMT

I’m attaching the RTT output with a payload of 500 bytes.

00> [01:47:03.586,883] <wrn> slm_uart_handler: Disabling UART RX: No free buffers.
00> [01:47:04.560,821] <inf> slm_at_host: Enter datamode
00> [01:47:04.977,172] <inf> slm_at_host: time limit reached
00> [01:47:04.977,569] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002e4d0
00> [01:47:04.980,438] <inf> slm_mqtt: datamode send: 0
00> [01:47:04.980,804] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002e6c4
00> [01:47:06.567,687] <inf> slm_at_host: time limit reached
00> [01:47:06.568,084] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002e6c4
00> [01:47:06.576,904] <inf> slm_mqtt: datamode send: 0
00> [01:47:06.577,270] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002e8b8
00> [01:47:08.166,534] <inf> slm_at_host: time limit reached
00> [01:47:08.166,931] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002e8b8
00> [01:47:08.175,720] <inf> slm_mqtt: datamode send: 0
00> [01:47:08.176,086] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002eaac
00> [01:47:09.767,272] <inf> slm_at_host: time limit reached
00> [01:47:09.767,669] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002eaac
00> [01:47:09.776,458] <inf> slm_mqtt: datamode send: 0
00> [01:47:09.776,824] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002eca0
00> [01:47:11.366,699] <inf> slm_at_host: time limit reached
00> [01:47:11.367,095] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002eca0
00> [01:47:11.375,946] <inf> slm_mqtt: datamode send: 0
00> [01:47:11.376,281] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002ee94
00> [01:47:12.966,949] <inf> slm_at_host: time limit reached
00> [01:47:12.967,346] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002ee94
00> [01:47:12.970,581] <inf> slm_mqtt: datamode send: 0
00> [01:47:12.970,947] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002f088
00> [01:47:14.566,375] <inf> slm_at_host: time limit reached
00> [01:47:14.566,772] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002f088
00> [01:47:14.575,592] <inf> slm_mqtt: datamode send: 0
00> [01:47:14.575,958] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002f27c
00> [01:47:16.166,320] <inf> slm_at_host: time limit reached
00> [01:47:16.166,717] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002f27c
00> [01:47:16.169,525] <inf> slm_mqtt: datamode send: 0
00> [01:47:16.169,891] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002f470
00> [01:47:17.767,456] <inf> slm_at_host: time limit reached
00> [01:47:17.767,852] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002f470
00> [01:47:17.776,672] <inf> slm_mqtt: datamode send: 0
00> [01:47:17.777,008] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002f664
00> [01:47:19.366,882] <inf> slm_at_host: time limit reached
00> [01:47:19.367,279] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002f664
00> [01:47:19.376,098] <inf> slm_mqtt: datamode send: 0
00> [01:47:19.376,464] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002f858
00> [01:47:20.967,193] <inf> slm_at_host: time limit reached
00> [01:47:20.967,590] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002f858
00> [01:47:20.976,409] <inf> slm_mqtt: datamode send: 0
00> [01:47:20.976,776] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002fa4c
00> [01:47:22.566,802] <inf> slm_at_host: time limit reached
00> [01:47:22.567,199] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002fa4c
00> [01:47:22.575,988] <inf> slm_mqtt: datamode send: 0
00> [01:47:22.576,354] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002fc40
00> [01:47:24.168,029] <inf> slm_at_host: time limit reached
00> [01:47:24.168,426] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002fc40
00> [01:47:24.171,203] <inf> slm_mqtt: datamode send: 0
00> [01:47:24.171,569] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002fe34
00> [01:47:25.766,632] <inf> slm_at_host: time limit reached
00> [01:47:25.767,028] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002fe34
00> [01:47:25.775,817] <inf> slm_mqtt: datamode send: 0
00> [01:47:25.776,184] <inf> slm_at_host: Raw send: size_send: 0, data 0x20030028
00> [01:47:27.367,645] <inf> slm_at_host: time limit reached
00> [01:47:27.368,041] <inf> slm_at_host: Raw send: size_send: 500, data 0x20030028
00> [01:47:27.372,039] <inf> slm_mqtt: datamode send: 0
00> [01:47:27.372,406] <inf> slm_at_host: Raw send: size_send: 0, data 0x2003021c
00> [01:47:28.968,292] <inf> slm_at_host: time limit reached
00> [01:47:28.968,688] <inf> slm_at_host: Raw send: size_send: 500, data 0x2003021c
00> [01:47:28.977,478] <inf> slm_mqtt: datamode send: 0
00> [01:47:28.977,844] <inf> slm_at_host: Raw send: size_send: 0, data 0x20030410
00> [01:47:30.569,183] <inf> slm_at_host: time limit reached
00> [01:47:30.569,580] <inf> slm_at_host: Raw send: size_send: 192, data 0x20030410
00> [01:47:30.570,037] <err> slm_mqtt: Datamode buffer overflow
00> [01:47:30.570,404] <wrn> slm_at_host: Raw send failed, 192 dropped
00> [01:47:30.570,800] <inf> slm_at_host: Raw send: size_send: 308, data 0x2002e4d0
00> [01:47:30.571,228] <wrn> slm_at_host: no handler, 308 dropped
00> [01:47:30.571,624] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002e604
00> [01:47:40.713,073] <wrn> slm_at_host: Data pipe broken. Dropping data until datamode is terminated.
00> [01:47:40.713,562] <wrn> slm_at_host: Terminating datamode, 0 dropped
00> [01:47:40.714,019] <inf> slm_at_host: Exit datamode
00> [01:47:40.857,452] <err> slm_mqtt: ZSOCK_POLLERR
00> [01:47:40.857,940] <err> slm_mqtt: Abort MQTT connection (error -5)
00> [01:47:40.858,764] <inf> slm_mqtt: MQTT thread terminated

import serial
import time
import hexdump

# Configurações
PORT = 'COM7'
BAUDRATE = 115200
TIMEOUT = 0.5

at_commands = [
    'AT+CFUN=0',
    'AT%POWERCLASS=5',
    'AT%XSYSTEMMODE=1,0,0,0',
    'AT+CFUN=1',
    'AT+CFUN?',
    'AT+COPS=1,2,"72405"',
    'AT+CGDCONT=1,"IP","em"',
    #'AT+CGDCONT=1,"IP","waterlog.claro.com.br"',
    'AT+CEREG=1',
    'AT+COPS?',
    'AT+CEREG?',
    'AT#XMQTTCFG="clientId-NdUYzNW5CM",60,1',
    'AT#XMQTTCON=1,"","","XXXXXXXXX",1883',
    'AT#XMQTTPUB="test/consumo/nrf9151","",2,0',
]

def generate_payload(bytes=4000):
    #return ''.join([str(v) for v in range(0,4096)])
    payload = ['0'] * bytes
    cont = 0
    for i in range(0, bytes):
        payload[i] = str(cont)
        cont += 1
        if cont > 9:
            cont = 0
    return ''.join(payload)

def send_at_command(ser, command):
    print(f"Enviando: {command}")
    ser.write((command + '\r\n').encode())
    ser.flush()

    response = []
    while True:
        line = ser.readline().decode(errors='ignore')
        if not line:
            break
        stripped_line = line.strip()
        if stripped_line:
            response.append(stripped_line)
            if stripped_line in ('OK', 'ERROR'):
                break

    print("Resposta:")
    print('\n'.join(response))
    print("-" * 30)
    return response

def wait_for_mqtt_event(ser, expected_evt_type, expected_result=0, timeout=10):
    print(f"Aguardando evento {expected_evt_type},{expected_result}...")
    start_time = time.time()
    while (time.time() - start_time) < timeout:
        line = ser.readline().decode(errors='ignore').strip()
        if line:
            print(f"Recebido: {line}")
            if line.startswith('#XMQTTEVT:'):
                try:
                    parts = line.split(':')[1].split(',')
                    evt_type = int(parts[0].strip())
                    result = int(parts[1].strip())
                    if evt_type == expected_evt_type and result == expected_result:
                        return True
                except:
                    pass
        else:
            time.sleep(0.1)
    print(f"Timeout aguardando evento {expected_evt_type},{expected_result}")
    return False

def main():
    try:
        payload_total = generate_payload(500)

        with serial.Serial(PORT, BAUDRATE, timeout=TIMEOUT) as ser:
            print(f"Conectado à porta {PORT} a {BAUDRATE} bps.")
            time.sleep(2)

            ser.write(b'+++')
            ser.write(b'AT\r\n')


            for cmd in at_commands:
                if cmd == 'AT+CEREG?':
                    while True:
                        response = send_at_command(ser, cmd)
                        cereg_ok = any(line.startswith('+CEREG: ') and (('1,5' in line) or ('1,1' in line)) for line in response)
                        if cereg_ok:
                            print("Registrado na rede com sucesso.")
                            break
                        else:
                            print("Aguardando registro na rede... Tentando novamente em 5 segundos.")
                            time.sleep(5)
                elif cmd.startswith('AT#XMQTTCON'):
                    send_at_command(ser, cmd)
                    wait_for_mqtt_event(ser, expected_evt_type=0)
                elif cmd.startswith('AT#XMQTTPUB') and '""' in cmd:
                    send_at_command(ser, cmd)
                    print("Entrando em modo de dados. Iniciando envios de payloads...")

                    for i in range(74):
                        print(f"\n[Payload {i+1}/74]")

                        # Horário real de envio
                        t_envio = time.strftime("%H:%M:%S")
                        print(f"[{t_envio}] Enviando payload {i+1}")
                        ser.write(payload_total.encode())
                        ser.flush()

                        # Esperar evento e registrar horário real de recepção
                        t_ini_espera = time.time()
                        while (time.time() - t_ini_espera) < 10:
                            line = ser.readline()
                            #hexdump.hexdump(line,result='print')                            
                            line = line.decode(errors='ignore').strip()
                            if line:
                                t_recebido = time.strftime("%H:%M:%S")
                                print(f"[{t_recebido}] Recebido: {line}")
                                if line.startswith('#XMQTTEVT:'):
                                    try:
                                        parts = line.split(':')[1].split(',')
                                        evt_type = int(parts[0].strip())
                                        result = int(parts[1].strip())
                                        if evt_type == 6 and result == 0:
                                            break  # Evento correto recebido
                                    except:
                                        pass
                            else:
                                time.sleep(0.1)

                        else:
                            print(f"[{time.strftime('%H:%M:%S')}] Timeout aguardando evento 6,0. Abortando.")
                            break

                    ser.write(b'+++')
                    print("Envio finalizado. Saindo do modo de dados.")
                    ser.write(b'AT+CFUN=4\r\n')
                    #ser.write(b'AT#XSLEEP=1\r\n')
                else:
                    send_at_command(ser, cmd)

    except serial.SerialException as e:
        print(f"Erro na serial: {e}")
    except Exception as e:
        print(f"Erro inesperado: {e}")

if __name__ == '__main__':
    main()

And I tried with cts/rts enabled.

00> *** Booting nRF Connect SDK v3.0.0-3bfc46578e42 ***
00> *** Using Zephyr OS v4.0.99-3e0ce7636fa6 ***
00> [00:00:00.255,096] <inf> at_cmd_custom: Custom AT commands enabled with 62 entries.
00> [00:00:00.261,657] <inf> fs_nvs: 2 Sectors of 4096 bytes
00> [00:00:00.262,023] <inf> fs_nvs: alloc wra: 0, fe8
00> [00:00:00.262,390] <inf> fs_nvs: data wra: 0, 0
00> [00:00:00.528,167] <inf> slm: lib_modem init: 0
00> [00:00:00.528,564] <inf> mcuboot_util: Image index: 0, Swap type: none
00> [00:00:00.528,961] <inf> slm: Serial LTE Modem
00> [00:00:00.530,181] <inf> slm_uart_handler: UART baud: 115200 d/p/s-bits: 3/0/1 HWFC: 1
00> [00:00:00.530,792] <inf> slm_at_host: at_host init done
00> [00:01:46.992,309] <wrn> slm_uart_handler: Disabling UART RX: No free buffers.
00> [00:01:58.000,244] <inf> slm_at_host: Enter datamode
00> [00:01:58.416,625] <inf> slm_at_host: time limit reached
00> [00:01:58.417,053] <inf> slm_at_host: Raw send: size_send: 500, data 0x20029f08
00> [00:01:58.419,372] <inf> slm_mqtt: datamode send: 0
00> [00:01:58.419,738] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a0fc
00> [00:01:59.997,009] <inf> slm_at_host: time limit reached
00> [00:01:59.997,436] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002a0fc
00> [00:02:00.005,889] <inf> slm_mqtt: datamode send: 0
00> [00:02:00.006,256] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a2f0
00> [00:02:01.598,205] <inf> slm_at_host: time limit reached
00> [00:02:01.598,632] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002a2f0
00> [00:02:01.607,086] <inf> slm_mqtt: datamode send: 0
00> [00:02:01.607,452] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a4e4
00> [00:02:03.197,052] <inf> slm_at_host: time limit reached
00> [00:02:03.197,479] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002a4e4
00> [00:02:03.205,932] <inf> slm_mqtt: datamode send: 0
00> [00:02:03.206,298] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a6d8
00> [00:02:04.798,309] <inf> slm_at_host: time limit reached
00> [00:02:04.798,736] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002a6d8
00> [00:02:04.801,269] <inf> slm_mqtt: datamode send: 0
00> [00:02:04.801,605] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a8cc
00> [00:02:06.397,186] <inf> slm_at_host: time limit reached
00> [00:02:06.397,613] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002a8cc
00> [00:02:06.400,726] <inf> slm_mqtt: datamode send: 0
00> [00:02:06.401,092] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002aac0
00> [00:02:07.997,650] <inf> slm_at_host: time limit reached
00> [00:02:07.998,077] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002aac0
00> [00:02:08.006,530] <inf> slm_mqtt: datamode send: 0
00> [00:02:08.006,896] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002acb4
00> [00:02:09.598,236] <inf> slm_at_host: time limit reached
00> [00:02:09.598,663] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002acb4
00> [00:02:09.607,116] <inf> slm_mqtt: datamode send: 0
00> [00:02:09.607,482] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002aea8
00> [00:02:11.196,655] <inf> slm_at_host: time limit reached
00> [00:02:11.197,082] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002aea8
00> [00:02:11.205,535] <inf> slm_mqtt: datamode send: 0
00> [00:02:11.205,902] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002b09c
00> [00:02:12.802,734] <inf> slm_at_host: time limit reached
00> [00:02:12.803,161] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002b09c
00> [00:02:12.805,603] <inf> slm_mqtt: datamode send: 0
00> [00:02:12.805,969] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002b290
00> [00:02:14.399,047] <inf> slm_at_host: time limit reached
00> [00:02:14.399,475] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002b290
00> [00:02:14.407,928] <inf> slm_mqtt: datamode send: 0
00> [00:02:14.408,294] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002b484
00> [00:02:15.996,459] <inf> slm_at_host: time limit reached
00> [00:02:15.996,887] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002b484
00> [00:02:15.999,145] <inf> slm_mqtt: datamode send: 0
00> [00:02:15.999,481] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002b678
00> [00:02:17.606,536] <inf> slm_at_host: time limit reached
00> [00:02:17.606,964] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002b678
00> [00:02:17.615,417] <inf> slm_mqtt: datamode send: 0
00> [00:02:17.615,783] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002b86c
00> [00:02:19.198,425] <inf> slm_at_host: time limit reached
00> [00:02:19.198,852] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002b86c
00> [00:02:19.207,305] <inf> slm_mqtt: datamode send: 0
00> [00:02:19.207,672] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002ba60
00> [00:02:20.710,235] <inf> slm_at_host: time limit reached
00> [00:02:20.710,662] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002ba60
00> [00:02:20.719,116] <inf> slm_mqtt: datamode send: 0
00> [00:02:20.719,482] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002bc54
00> [00:02:22.397,430] <inf> slm_at_host: time limit reached
00> [00:02:22.397,857] <inf> slm_at_host: Raw send: size_send: 500, data 0x2002bc54
00> [00:02:22.406,311] <inf> slm_mqtt: datamode send: 0
00> [00:02:22.406,677] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002be48
00> [00:02:23.986,785] <inf> slm_at_host: time limit reached
00> [00:02:23.987,213] <inf> slm_at_host: Raw send: size_send: 192, data 0x2002be48
00> [00:02:23.987,670] <err> slm_mqtt: Datamode buffer overflow
00> [00:02:23.988,037] <wrn> slm_at_host: Raw send failed, 192 dropped
00> [00:02:23.988,433] <inf> slm_at_host: Raw send: size_send: 308, data 0x20029f08
00> [00:02:23.988,891] <wrn> slm_at_host: no handler, 308 dropped
00> [00:02:23.989,288] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a03c
00> [00:04:34.597,320] <err> slm_mqtt: ZSOCK_POLLERR
00> [00:04:34.597,656] <err> slm_mqtt: Abort MQTT connection (error -5)
00> [00:04:34.598,510] <inf> slm_mqtt: MQTT thread terminated

RE: Low data throughput on nRF9151DK compared to nRF9160

l0cszp — Mon, 11 Aug 2025 16:55:49 GMT

I’m attaching the RTT output from my test below for reference.
This was captured using CONFIG_USE_SEGGER_RTT=y and CONFIG_LOG_BACKEND_RTT=y in my nRF Connect SDK v3.0.2 build.

00> *** Booting nRF Connect SDK v3.0.2-89ba1294ac9b ***
00> *** Using Zephyr OS v4.0.99-f791c49f492c ***
00> [00:00:00.255,126] <inf> at_cmd_custom: Custom AT commands enabled with 62 entries.
00> [00:00:00.261,474] <inf> fs_nvs: 2 Sectors of 4096 bytes
00> [00:00:00.261,840] <inf> fs_nvs: alloc wra: 0, fe8
00> [00:00:00.262,176] <inf> fs_nvs: data wra: 0, 0
00> [00:00:00.522,491] <inf> nrf_modem_lib_trace: Trace thread ready
00> [00:00:00.530,944] <inf> nrf_modem_lib_trace: Trace level override: 2
00> [00:00:00.538,421] <inf> slm: lib_modem init: 0
00> [00:00:00.538,818] <inf> mcuboot_util: Image index: 0, Swap type: none
00> [00:00:00.539,184] <inf> slm: Serial LTE Modem
00> [00:00:00.540,283] <inf> slm_uart_handler: UART baud: 115200 d/p/s-bits: 3/0/1 HWFC: 0
00> [00:00:00.540,863] <inf> slm_at_host: at_host init done
00> [00:01:18.437,103] <err> slm_at_host: AT command syntax invalid: ATAT+CFUN=0
00> [00:01:24.268,737] <inf> slm_at_host: Enter datamode
00> [00:01:24.770,843] <inf> slm_at_host: time limit reached
00> [00:01:24.771,240] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:01:24.777,587] <inf> slm_mqtt: datamode send: 0
00> [00:01:24.777,954] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:01:26.256,072] <inf> slm_at_host: time limit reached
00> [00:01:26.256,469] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:01:26.268,341] <inf> slm_mqtt: datamode send: 0
00> [00:01:26.268,707] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:01:27.807,006] <inf> slm_at_host: time limit reached
00> [00:01:27.807,403] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:01:27.819,519] <inf> slm_mqtt: datamode send: 0
00> [00:01:27.819,854] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:01:29.240,936] <inf> slm_at_host: time limit reached
00> [00:01:29.241,333] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:01:29.248,992] <inf> slm_mqtt: datamode send: 0
00> [00:01:29.249,359] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:01:30.841,156] <inf> slm_at_host: time limit reached
00> [00:01:30.841,552] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:01:30.847,381] <inf> slm_mqtt: datamode send: 0
00> [00:01:30.847,747] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:01:32.441,131] <inf> slm_at_host: time limit reached
00> [00:01:32.441,528] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:01:32.447,998] <inf> slm_mqtt: datamode send: 0
00> [00:01:32.448,333] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:01:34.040,313] <inf> slm_at_host: time limit reached
00> [00:01:34.040,710] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:01:34.046,539] <inf> slm_mqtt: datamode send: 0
00> [00:01:34.046,905] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:01:35.642,120] <inf> slm_at_host: time limit reached
00> [00:01:35.642,517] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:01:35.648,193] <inf> slm_mqtt: datamode send: 0
00> [00:01:35.648,559] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:01:37.092,529] <inf> slm_at_host: time limit reached
00> [00:01:37.092,926] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:01:37.105,041] <inf> slm_mqtt: datamode send: 0
00> [00:01:37.105,377] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:01:38.841,369] <inf> slm_at_host: time limit reached
00> [00:01:38.841,766] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:01:38.847,808] <inf> slm_mqtt: datamode send: 0
00> [00:01:38.848,175] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:01:40.286,499] <inf> slm_at_host: time limit reached
00> [00:01:40.286,895] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:01:40.299,011] <inf> slm_mqtt: datamode send: 0
00> [00:01:40.299,346] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:01:41.720,855] <inf> slm_at_host: time limit reached
00> [00:01:41.721,252] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:01:41.728,515] <inf> slm_mqtt: datamode send: 0
00> [00:01:41.728,881] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:01:43.321,868] <inf> slm_at_host: time limit reached
00> [00:01:43.322,265] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:01:43.327,972] <inf> slm_mqtt: datamode send: 0
00> [00:01:43.328,308] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:01:44.815,826] <inf> slm_at_host: time limit reached
00> [00:01:44.816,223] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:01:44.828,094] <inf> slm_mqtt: datamode send: 0
00> [00:01:44.828,460] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:01:46.365,112] <inf> slm_at_host: time limit reached
00> [00:01:46.365,509] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:01:46.373,138] <inf> slm_mqtt: datamode send: 0
00> [00:01:46.373,504] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:01:47.801,940] <inf> slm_at_host: time limit reached
00> [00:01:47.802,337] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:01:47.808,166] <inf> slm_mqtt: datamode send: 0
00> [00:01:47.808,532] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:01:49.296,417] <inf> slm_at_host: time limit reached
00> [00:01:49.296,813] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:01:49.308,563] <inf> slm_mqtt: datamode send: 0
00> [00:01:49.308,929] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:01:50.845,489] <inf> slm_at_host: time limit reached
00> [00:01:50.845,886] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:01:50.858,001] <inf> slm_mqtt: datamode send: 0
00> [00:01:50.858,337] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:01:52.281,799] <inf> slm_at_host: time limit reached
00> [00:01:52.282,196] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:01:52.287,902] <inf> slm_mqtt: datamode send: 0
00> [00:01:52.288,238] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:01:53.726,287] <inf> slm_at_host: time limit reached
00> [00:01:53.726,684] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:01:53.734,344] <inf> slm_mqtt: datamode send: 0
00> [00:01:53.734,710] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:01:55.161,193] <inf> slm_at_host: time limit reached
00> [00:01:55.161,590] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:01:55.167,663] <inf> slm_mqtt: datamode send: 0
00> [00:01:55.167,999] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:01:56.656,524] <inf> slm_at_host: time limit reached
00> [00:01:56.656,921] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:01:56.669,036] <inf> slm_mqtt: datamode send: 0
00> [00:01:56.669,372] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:01:58.211,486] <inf> slm_at_host: time limit reached
00> [00:01:58.211,883] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:01:58.219,573] <inf> slm_mqtt: datamode send: 0
00> [00:01:58.219,940] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:01:59.643,646] <inf> slm_at_host: time limit reached
00> [00:01:59.644,042] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:01:59.650,115] <inf> slm_mqtt: datamode send: 0
00> [00:01:59.650,451] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:01.091,339] <inf> slm_at_host: time limit reached
00> [00:02:01.091,735] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:01.103,851] <inf> slm_mqtt: datamode send: 0
00> [00:02:01.104,187] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:02.522,186] <inf> slm_at_host: time limit reached
00> [00:02:02.522,583] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:02.529,602] <inf> slm_mqtt: datamode send: 0
00> [00:02:02.529,968] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:04.122,894] <inf> slm_at_host: time limit reached
00> [00:02:04.123,291] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:04.128,997] <inf> slm_mqtt: datamode send: 0
00> [00:02:04.129,333] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:05.573,272] <inf> slm_at_host: time limit reached
00> [00:02:05.573,669] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:05.585,571] <inf> slm_mqtt: datamode send: 0
00> [00:02:05.585,906] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:07.003,326] <inf> slm_at_host: time limit reached[0m
00> [00:02:07.003,723] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:07.009,552] <inf> slm_mqtt: datamode send: 0
00> [00:02:07.009,887] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:08.496,765] <inf> slm_at_host: time limit reached
00> [00:02:08.497,161] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:08.508,911] <inf> slm_mqtt: datamode send: 0
00> [00:02:08.509,246] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:10.046,478] <inf> slm_at_host: time limit reached
00> [00:02:10.046,875] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:10.054,504] <inf> slm_mqtt: datamode send: 0
00> [00:02:10.054,870] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:11.483,337] <inf> slm_at_host: time limit reached
00> [00:02:11.483,734] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:11.489,807] <inf> slm_mqtt: datamode send: 0
00> [00:02:11.490,142] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:12.979,034] <inf> slm_at_host: time limit reached
00> [00:02:12.979,431] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:12.987,121] <inf> slm_mqtt: datamode send: 0
00> [00:02:12.987,487] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:14.362,762] <inf> slm_at_host: time limit reached
00> [00:02:14.363,159] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:14.369,232] <inf> slm_mqtt: datamode send: 0
00> [00:02:14.369,567] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:15.962,432] <inf> slm_at_host: time limit reached
00> [00:02:15.962,829] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:15.968,658] <inf> slm_mqtt: datamode send: 0
00> [00:02:15.969,024] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:17.407,989] <inf> slm_at_host: time limit reached
00> [00:02:17.408,447] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:17.415,771] <inf> slm_mqtt: datamode send: 0
00> [00:02:17.416,137] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:18.842,834] <inf> slm_at_host: time limit reached
00> [00:02:18.843,231] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:18.850,250] <inf> slm_mqtt: datamode send: 0
00> [00:02:18.850,616] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:20.443,359] <inf> slm_at_host: time limit reached
00> [00:02:20.443,756] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:20.449,829] <inf> slm_mqtt: datamode send: 0
00> [00:02:20.450,164] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:21.892,242] <inf> slm_at_host: time limit reached
00> [00:02:21.892,639] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:21.900,054] <inf> slm_mqtt: datamode send: 0
00> [00:02:21.900,421] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:23.334,838] <inf> slm_at_host: time limit reached
00> [00:02:23.335,235] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:23.342,346] <inf> slm_mqtt: datamode send: 0
00> [00:02:23.342,712] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:24.817,687] <inf> slm_at_host: time limit reached
00> [00:02:24.818,084] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:24.830,169] <inf> slm_mqtt: datamode send: 0
00> [00:02:24.830,535] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:26.368,286] <inf> slm_at_host: time limit reached
00> [00:02:26.368,682] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:26.376,159] <inf> slm_mqtt: datamode send: 0
00> [00:02:26.376,525] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:27.802,947] <inf> slm_at_host: time limit reached
00> [00:02:27.803,344] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:27.809,387] <inf> slm_mqtt: datamode send: 0
00> [00:02:27.809,753] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:29.255,493] <inf> slm_at_host: time limit reached
00> [00:02:29.255,889] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:29.267,639] <inf> slm_mqtt: datamode send: 0
00> [00:02:29.268,005] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:30.847,839] <inf> slm_at_host: time limit reached
00> [00:02:30.848,236] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:30.859,985] <inf> slm_mqtt: datamode send: 0
00> [00:02:30.860,321] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:32.282,897] <inf> slm_at_host: time limit reached
00> [00:02:32.283,294] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:32.289,337] <inf> slm_mqtt: datamode send: 0
00> [00:02:32.289,703] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:33.727,783] <inf> slm_at_host: time limit reached
00> [00:02:33.728,179] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:33.735,473] <inf> slm_mqtt: datamode send: 0
00> [00:02:33.735,839] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:35.163,970] <inf> slm_at_host: time limit reached
00> [00:02:35.164,367] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:35.170,227] <inf> slm_mqtt: datamode send: 0
00> [00:02:35.170,562] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:36.658,416] <inf> slm_at_host: time limit reached
00> [00:02:36.658,813] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:36.670,928] <inf> slm_mqtt: datamode send: 0
00> [00:02:36.671,264] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:38.208,740] <inf> slm_at_host: time limit reached
00> [00:02:38.209,136] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:38.216,613] <inf> slm_mqtt: datamode send: 0
00> [00:02:38.217,010] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:39.644,958] <inf> slm_at_host: time limit reached
00> [00:02:39.645,355] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:39.651,184] <inf> slm_mqtt: datamode send: 0
00> [00:02:39.651,550] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:41.094,970] <inf> slm_at_host: time limit reached
00> [00:02:41.095,367] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:41.107,452] <inf> slm_mqtt: datamode send: 0
00> [00:02:41.107,818] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:42.843,505] <inf> slm_at_host: time limit reached
00> [00:02:42.843,902] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:42.849,578] <inf> slm_mqtt: datamode send: 0
00> [00:02:42.849,945] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:44.288,848] <inf> slm_at_host: time limit reached
00> [00:02:44.289,245] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:44.301,361] <inf> slm_mqtt: datamode send: 0
00> [00:02:44.301,696] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:45.724,426] <inf> slm_at_host: time limit reached
00> [00:02:45.724,822] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:45.730,865] <inf> slm_mqtt: datamode send: 0
00> [00:02:45.731,231] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:47.174,316] <inf> slm_at_host: time limit reached
00> [00:02:47.174,713] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:47.186,828] <inf> slm_mqtt: datamode send: 0
00> [00:02:47.187,194] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:48.603,637] <inf> slm_at_host: time limit reached
00> [00:02:48.604,034] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:48.609,710] <inf> slm_mqtt: datamode send: 0[0m
00> [00:02:48.610,076] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:50.104,644] <inf> slm_at_host: time limit reached
00> [00:02:50.105,041] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:50.112,243] <inf> slm_mqtt: datamode send: 0
00> [00:02:50.112,579] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:51.484,710] <inf> slm_at_host: time limit reached
00> [00:02:51.485,107] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:51.491,180] <inf> slm_mqtt: datamode send: 0
00> [00:02:51.491,516] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:52.933,563] <inf> slm_at_host: time limit reached
00> [00:02:52.933,959] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:52.945,709] <inf> slm_mqtt: datamode send: 0
00> [00:02:52.946,044] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:54.685,302] <inf> slm_at_host: time limit reached
00> [00:02:54.685,699] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:54.691,558] <inf> slm_mqtt: datamode send: 0
00> [00:02:54.691,894] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:56.284,667] <inf> slm_at_host: time limit reached
00> [00:02:56.285,064] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:56.292,388] <inf> slm_mqtt: datamode send: 0
00> [00:02:56.292,755] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:57.783,508] <inf> slm_at_host: time limit reached
00> [00:02:57.783,905] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:57.795,776] <inf> slm_mqtt: datamode send: 0
00> [00:02:57.796,142] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:02:59.484,954] <inf> slm_at_host: time limit reached
00> [00:02:59.485,351] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:02:59.491,210] <inf> slm_mqtt: datamode send: 0
00> [00:02:59.491,546] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:03:00.927,734] <inf> slm_at_host: time limit reached
00> [00:03:00.928,131] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:03:00.939,880] <inf> slm_mqtt: datamode send: 0
00> [00:03:00.940,216] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:03:02.364,624] <inf> slm_at_host: time limit reached
00> [00:03:02.365,020] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:03:02.371,063] <inf> slm_mqtt: datamode send: 0
00> [00:03:02.371,429] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:03:03.808,929] <inf> slm_at_host: time limit reached
00> [00:03:03.809,326] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:03:03.816,589] <inf> slm_mqtt: datamode send: 0
00> [00:03:03.816,955] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:03:05.410,766] <inf> slm_at_host: time limit reached
00> [00:03:05.411,163] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:03:05.423,278] <inf> slm_mqtt: datamode send: 0
00> [00:03:05.423,614] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:03:06.845,458] <inf> slm_at_host: time limit reached
00> [00:03:06.845,855] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:03:06.853,057] <inf> slm_mqtt: datamode send: 0
00> [00:03:06.853,393] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:03:08.290,405] <inf> slm_at_host: time limit reached
00> [00:03:08.290,802] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:03:08.298,034] <inf> slm_mqtt: datamode send: 0
00> [00:03:08.298,400] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:03:09.740,203] <inf> slm_at_host: time limit reached
00> [00:03:09.740,600] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:03:09.746,459] <inf> slm_mqtt: datamode send: 0
00> [00:03:09.746,826] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:03:11.221,313] <inf> slm_at_host: time limit reached
00> [00:03:11.221,710] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:03:11.227,386] <inf> slm_mqtt: datamode send: 0
00> [00:03:11.227,752] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:03:12.924,346] <inf> slm_at_host: time limit reached
00> [00:03:12.924,743] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:03:12.930,603] <inf> slm_mqtt: datamode send: 0
00> [00:03:12.930,938] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:03:14.384,155] <inf> slm_at_host: time limit reached
00> [00:03:14.384,552] <inf> slm_at_host: Raw send: size_send: 4096, data 0x2002a47c
00> [00:03:14.392,120] <inf> slm_mqtt: datamode send: 0
00> [00:03:14.392,486] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:03:15.312,927] <inf> slm_at_host: Raw send: size_send: 0, data 0x2002a47c
00> [00:03:15.313,446] <inf> slm_at_host: Exit datamode
00> [00:03:15.346,221] <err> slm_mqtt: ZSOCK_POLLERR
00> [00:03:15.346,710] <err> slm_mqtt: Abort MQTT connection (error -5)
00> [00:03:15.347,503] <inf> slm_mqtt: MQTT thread terminated
00> [00:03:15.981,475] <inf> slm: Entering sleep.

RE: Low data throughput on nRF9151DK compared to nRF9160

l0cszp — Fri, 08 Aug 2025 16:46:43 GMT

Hi Dejan,

When I say minor adjustments, I mean only pin-related changes and SDK version differences.
For the nRF9160 tests, I used NCS v2.7.0.

Yes – the script is exactly the same. I tested it using:

A UART converter with the script attached;
The same MCU (STM32L4), which was also tested with the nRF9160, producing the same results.

Regarding the 921600 baud rate, in the first print attached you can see that I used this baud rate and the modem responded without issues.

For the modem trace, in the fifth and sixth print attached you’ll find the trace captured using the Cellular Monitor.
Do you prefer that I provide this trace in another format?

As for the MQTT broker:

We tested both our private AWS broker and a public broker.
Throughput differences were negligible.
The public broker was also used for the nRF9160 tests, with the same SIM card.

About the other suggestions you mentioned (RTT, timestamps, prj.conf, pins), I will implement them and return with the results as soon as possible.

RE: Low data throughput on nRF9151DK compared to nRF9160

dejans — Fri, 08 Aug 2025 14:36:19 GMT

Hi,

[quote user=""]running the same firmware (with minor adjustments) on the nRF9151DK, the same 300 kBytes take about 2 minutes to transmit.[/quote]

Can you please specify minor adjustments between nrf9160 and nrf9151? Are setups when using nrf9160 and nrf9151 identical?

Does nRF9160 use the same NCS version, the same script and server for MQTT?

Do you use virtual COM ports? Baudrate of 921600 is not supported with virtual COM ports.

CONFIG_UART_2_NRF_HW_ASYNC is deprecated. Instead, CONFIG_UART_NRFX_UARTE_ENHANCED_RX should be used.
Likely, you should set CONFIG_SLM_UART_RX_BUF_SIZE to 1500 so that 3 buffers are able to store 4 KB.

Can you provide modem trace (-Dserial_lte_modem_SNIPPET='nrf91-modem-trace-uart)?

It might be useful if you could provide debug RTT log.

It could also be useful to have millisecond level timestamps from the script to better see where the time has been spent. You could also provide the same result for nrf9160.

Best regards,
Dejan

RE: Low data throughput on nRF9151DK compared to nRF9160

l0cszp — Thu, 07 Aug 2025 21:37:33 GMT

Please find attached the Celular Monitor output as evidence for the issue described below.

RE: Low data throughput on nRF9151DK compared to nRF9160

l0cszp — Thu, 07 Aug 2025 14:17:31 GMT

Hi Dejan,

Thanks for your response.

I don’t think the baudrate is the limiting factor in this case. I’ve tested the nRF9151-DK using both 115200 and 921600 baudrates, and the data rate difference between the two is minimal.

As an example, In the print attached is sent 300 kB of data over MQTT using the nRF9151-DK. The full transfer took approximately 85 seconds, resulting in a measured throughput of:

- ~3.45 kB/s
- ~3529 bytes/s
- ~28.24 kbps

This is significantly below the theoretical maximum data rate for LTE Cat-M1, which can reach up to **300 kbps downlink** and **375 kbps uplink** under ideal conditions. This suggests that the limitation is likely not on the link layer or UART baudrate, but instead somewhere higher up — possibly in the modem’s internal processing, MQTT handling..

Here is a summary of my current setup:
- nRF Connect SDK: v3.0.2
- Toolchain: v3.0.2
- Modem firmware: nrf9151dk_mfw-2.0.2_sdk-3.0.0
- UART: Configured on UART2 with CONFIG_UART_2_NRF_HW_ASYNC=y and 921600 baudrate

I’m happy to provide logs or test additional configurations if needed.

# General system config
CONFIG_LOG=y
CONFIG_ASSERT=y
CONFIG_ASSERT_VERBOSE=n
CONFIG_LOG_DEFAULT_LEVEL=3
CONFIG_STACK_SENTINEL=y
CONFIG_PICOLIBC_IO_FLOAT=y
CONFIG_RING_BUFFER=y
CONFIG_REBOOT=y
CONFIG_EVENTFD=y

# Segger RTT config
CONFIG_USE_SEGGER_RTT=y
CONFIG_RTT_CONSOLE=y
CONFIG_UART_CONSOLE=n
CONFIG_LOG_BACKEND_RTT=y
CONFIG_LOG_BACKEND_UART=n

# Networking
CONFIG_NETWORKING=y
CONFIG_NET_SOCKETS=y
CONFIG_NET_NATIVE=n
CONFIG_NET_IPV4=y
CONFIG_NET_IPV6=y

# Modem
CONFIG_NRF_MODEM_LIB=y
CONFIG_AT_CMD_CUSTOM=y
CONFIG_ZVFS_OPEN_MAX=8
CONFIG_NRF_MODEM_LIB_ON_FAULT_APPLICATION_SPECIFIC=y

# GPIO
CONFIG_GPIO=y
CONFIG_GPIO_NRFX=y

# UART interface
CONFIG_SERIAL=y
CONFIG_UART_USE_RUNTIME_CONFIGURE=y
CONFIG_UART_ASYNC_API=y
CONFIG_NRFX_TIMER2=y

# Stacks and heaps
CONFIG_MAIN_STACK_SIZE=4096
CONFIG_HEAP_MEM_POOL_SIZE=16384
CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=4096
CONFIG_AT_MONITOR_HEAP_SIZE=4096

# Power management
CONFIG_PM_DEVICE=y

# FOTA
CONFIG_HTTP_PARSER_URL=y
CONFIG_FOTA_DOWNLOAD=y
CONFIG_FOTA_DOWNLOAD_PROGRESS_EVT=y
CONFIG_DFU_TARGET=y
CONFIG_DOWNLOADER=y
CONFIG_DOWNLOADER_STACK_SIZE=4096
CONFIG_DOWNLOADER_MAX_FILENAME_SIZE=2048
CONFIG_BOOTLOADER_MCUBOOT=y
CONFIG_IMG_MANAGER=y

# Flash
CONFIG_FLASH=y
CONFIG_FLASH_PAGE_LAYOUT=y
CONFIG_FLASH_MAP=y
CONFIG_STREAM_FLASH=y
CONFIG_MPU_ALLOW_FLASH_WRITE=y
CONFIG_IMG_ERASE_PROGRESSIVELY=y

# Settings
CONFIG_SETTINGS=y
CONFIG_SETTINGS_NVS=y
CONFIG_NVS=y

# nRF Cloud
CONFIG_NRF_CLOUD=y
CONFIG_NRF_CLOUD_MQTT=y
CONFIG_NRF_CLOUD_FOTA=n
CONFIG_NRF_CLOUD_AGNSS=y
CONFIG_NRF_CLOUD_AGNSS_FILTERED=n
CONFIG_NRF_CLOUD_PGPS=n
CONFIG_NRF_CLOUD_LOCATION=y
CONFIG_NRF_CLOUD_LOG_LEVEL_INF=y
CONFIG_NRF_CLOUD_GPS_LOG_LEVEL_INF=y
CONFIG_NRF_CLOUD_CLIENT_ID_SRC_INTERNAL_UUID=y
CONFIG_NRF_CLOUD_WIFI_LOCATION_ENCODE_OPT_MAC_RSSI=y
CONFIG_DATE_TIME=y
CONFIG_MODEM_INFO=y
CONFIG_MODEM_INFO_ADD_DATE_TIME=n

# UUID and JWT
CONFIG_MODEM_JWT=y

# MQTT
CONFIG_MQTT_CLEAN_SESSION=y

# AT command helper
CONFIG_AT_PARSER=y
CONFIG_AT_MONITOR=y

# TF-M logging
CONFIG_TFM_LOG_LEVEL_SILENCE=y

# SLM specific
CONFIG_SLM_CUSTOMER_VERSION=""
CONFIG_SLM_EXTERNAL_XTAL=n
CONFIG_SLM_UART_RX_BUF_SIZE=512
CONFIG_SLM_UART_TX_BUF_SIZE=512
CONFIG_SLM_MQTTC_MESSAGE_BUFFER_LEN=4096
CONFIG_SLM_NRF_CLOUD=n

# Debug options (optional)
#CONFIG_LOG_BUFFER_SIZE=16384
#CONFIG_SLM_LOG_LEVEL_DBG=y
#CONFIG_LOG_PRINTK=n
#CONFIG_LOG_MODE_IMMEDIATE=y

/ {
	chosen {
		ncs,slm-uart = &uart2;
	};
};

&uart0 {
	compatible = "nordic,nrf-uarte";
	current-speed = <115200>;
	status = "disabled";
	pinctrl-0 = <&uart0_default>;
	pinctrl-1 = <&uart0_sleep>;
	pinctrl-names = "default", "sleep";
};

&uart2 {
	compatible = "nordic,nrf-uarte";
	current-speed = <921600>;
	status = "okay";
	pinctrl-0 = <&uart2_default_alt>;
	pinctrl-1 = <&uart2_sleep_alt>;
	pinctrl-names = "default", "sleep";
};

&i2c2 {
	status = "disabled";
};

&pinctrl {
	uart0_default: uart0_default {
		group1 {
			psels = <NRF_PSEL(UART_TX, 0, 27)>;
		};
		group2 {
			psels = <NRF_PSEL(UART_RX, 0, 26)>;
			bias-pull-up;
		};
	};

	uart0_sleep: uart0_sleep {
		group1 {
			psels = <NRF_PSEL(UART_TX, 0, 27)>,
			        <NRF_PSEL(UART_RX, 0, 26)>;
			low-power-enable;
		};
	};

	uart2_default_alt: uart2_default_alt {
		group1 {
			psels = <NRF_PSEL(UART_RX, 0, 11)>;
			bias-pull-up;
		};
		group2 {
			psels = <NRF_PSEL(UART_TX, 0, 10)>;
		};
	};

	uart2_sleep_alt: uart2_sleep_alt {
		group1 {
			psels = <NRF_PSEL(UART_TX, 0, 10)>,
			        <NRF_PSEL(UART_RX, 0, 11)>;
			low-power-enable;
		};
	};
};

&gd25wb256 {
	status = "okay";
};

&clock {
	status = "okay";
};

&timer2 {
	status = "okay";
};

&power {
	status = "okay";
};