nRF9160: Serial LTE modem + MQTT publish

RE: nRF9160: Serial LTE modem + MQTT publish

TimYang — Thu, 27 Jan 2022 02:57:06 GMT

I appreciate your help very much.

Sincerely,

Tim

RE: nRF9160: Serial LTE modem + MQTT publish

Charlie — Wed, 26 Jan 2022 13:45:32 GMT

Hi Tim,

1. AT#XMQTTPUB="nrf91/slm/mqtt/topic0",,2,0 # You can keep second parameter empty and configure the third option for QoS.

2. You need to add a proper delay between two messages depending on your network environment and message length(which affects time length for data transmassion). If your application needs a very high-frequency data update rate, you have to think about other solutions.

Best regards,

Charlie

RE: nRF9160: Serial LTE modem + MQTT publish

TimYang — Wed, 26 Jan 2022 09:01:38 GMT

Hi Charlie,

May I ask you some questions about MQTT message in JSON format?

Could I adjust the QoS level when I'm going to enable slm data mode?
I got an issue like below(JSON format content was divided into two separate messages) if I run my python code in high frequency(about once per second).

import serial

ser = serial.Serial()
ser.baudrate = 115200
ser.port = 'COM3'

# Connecting code...

message = {'timestamp': TIMESTAMP, 'pulse': PULSE, 'spo2': SPO2}
message_json = json.dumps(message).encode("ascii")
ser.write(message_json)

Is there anything I can do to prevent this problem?

Best regards,

Tim

RE: nRF9160: Serial LTE modem + MQTT publish

TimYang — Wed, 26 Jan 2022 02:38:40 GMT

Hi Charlie,

Thanks for your reply. I finally figured out why Link Monitor keeps sending me timed-out ERROR after I enabled data mode.😅

Best regards,

Tim

RE: nRF9160: Serial LTE modem + MQTT publish

Charlie — Tue, 25 Jan 2022 12:58:10 GMT

Hi Tim,

The correct way should be like the following steps:

1. AT#XMQTTPUB="nrf91/slm/mqtt/topic0" #enable slm data mode

2. {"msg":"Test Json publish"} # json format content, could be data in any format

3. +++ #Exit slm data mode. Link Monitor attaches CRLF always, this will not stop slm data mode, use serial terminals like use Teraterm, Termite on Windows and Cutecome on Ubuntu, they support sending only +++.

Best regards,

Charlie