Thingy:91 Serial LTE modem PSM

[Michal Mühlpachr]

I want to evaluate power consumption of nRF9160 used as AT command modem using Thingy:91 Serial LTE modem.

How to achieve lowest power consumption for Thingy:91 LTE Modem in PSM please ?

- Thingy:91 v1.0.0

- LTE modem app from ncs v1.4.0

- Modem firmware AT+CGMR mfw_nrf9160_1.2.2

- https://www.joulescope.com/

- NB IoT Vodafone CZ, +CEREG: 5,"AE38","000AC51F",9,,,"00000000","00000111"

After AT#XSLEEP=0 or AT#XSLEEP=0 I am getting ~90uA average power consumption measured on P1 (SB3 cutted).

I am not able to wake up nRF9160 by UART communication or button.

Tested with following prj.conf build options for Serial LTE modem app:

- default

- CONFIG_SLM_GPIO_WAKEUP = y

- CONFIG_SLM_GPIO_WAKEUP = y & CONFIG_SLM_INTERFACE_PIN = 26

There is not CONFIG_SLM_CONNECT_UART_0 in prj.conf as stated in documentation https://developer.nordicsemi.com/nRF_Connect_SDK/doc/1.4.0/nrf/applications/serial_lte_modem/doc/slm_description.html

but there is CONFIG_UART_0_NRF_HW_ASYNC_TIMER=2 - is it OK please ?

 

Whole default prj.conf from ncs v1.4.0:

# General config

CONFIG_LOG=y

CONFIG_LOG_DEFAULT_LEVEL=3

CONFIG_STACK_SENTINEL=y

CONFIG_NEWLIB_LIBC=y

CONFIG_NEWLIB_LIBC_FLOAT_PRINTF=y

CONFIG_RING_BUFFER=y

# Segger RTT

CONFIG_USE_SEGGER_RTT=y

CONFIG_RTT_CONSOLE=y

CONFIG_UART_CONSOLE=n

CONFIG_LOG_BACKEND_RTT=y

CONFIG_LOG_BACKEND_UART=n

# Network

CONFIG_NETWORKING=y

CONFIG_NET_SOCKETS=y

CONFIG_NET_NATIVE=n

# BSD library

CONFIG_BSD_LIBRARY=y

# Align the max FD entry to BSD_MAX_SOCKET_COUNT(8)

CONFIG_POSIX_MAX_FDS=8

# Enable below for modem trace

#CONFIG_BSD_LIBRARY_TRACE_ENABLED=y

# Use GPIO

CONFIG_GPIO=y

CONFIG_GPIO_NRFX=y

CONFIG_GPIO_NRF_P0=y

# UART interface

CONFIG_SERIAL=y

CONFIG_UART_ASYNC_API=y

CONFIG_NRFX_TIMER2=y

# LTE link control

CONFIG_LTE_LINK_CONTROL=y

CONFIG_LTE_AUTO_INIT_AND_CONNECT=n

# Stacks and heaps

CONFIG_MAIN_STACK_SIZE=4096

CONFIG_HEAP_MEM_POOL_SIZE=16384

CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=8192

# AT_CMD

# Enable AT_CMD debug for details

#CONFIG_AT_CMD_LOG_LEVEL_DBG=y

# Device power management

CONFIG_DEVICE_POWER_MANAGEMENT=y

# Enable SUPL client support

#CONFIG_SUPL_CLIENT_LIB=y

# FOTA

CONFIG_HTTP_PARSER_URL=y

CONFIG_FOTA_DOWNLOAD=y

CONFIG_FOTA_DOWNLOAD_PROGRESS_EVT=y

CONFIG_DFU_TARGET=y

CONFIG_DOWNLOAD_CLIENT=y

CONFIG_DOWNLOAD_CLIENT_STACK_SIZE=4096

CONFIG_BOOTLOADER_MCUBOOT=y

CONFIG_IMG_MANAGER=y

CONFIG_FLASH=y

CONFIG_IMG_ERASE_PROGRESSIVELY=y

# Application-specific

CONFIG_SLM_LOG_LEVEL_INF=y

# Enable GPIO wakeup if sleep is expected

#CONFIG_SLM_GPIO_WAKEUP=y

# Use UART_0 (when working with PC terminal)

CONFIG_UART_0_NRF_HW_ASYNC_TIMER=2

# Use UART_2 (when working with external MCU)

#CONFIG_SLM_CONNECT_UART_2=y

#CONFIG_UART_2_NRF_HW_ASYNC_TIMER=2

# Use optional TCP/TLS Proxy

#CONFIG_SLM_TCP_PROXY=y

# Use optional UDP/DTLS Proxy

#CONFIG_SLM_UDP_PROXY=y

[Michal Mühlpachr]

Hi, thank you for hints.

I have CONFIG_SLM_GPIO_WAKEUP=y and CONFIG_SLM_INTERFACE_PIN=26 in prj.conf.

In thingy91_nrf9160ns.overlay I have:

&uart1 {
status = "disabled";
};

&uart0 {
/delete-property/ hw-flow-control;
/delete-property/ rts-pin;
/delete-property/ cts-pin;
};

I am able to wake up nRF9160 by GPIO.

I am getting sometimes during nRF9160 wake up and always after closing serial port in nRF Connect LTE LInk Monitor those logs in nRF9160 RTT:

[00:00:07.882,720] <wrn> at_host: RX_STOPPED (4)
[00:00:07.882,720] <wrn> at_host: RX_STOPPED (8)
[00:00:07.882,812] <wrn> at_host: RX_STOPPED (4)
[00:00:07.882,843] <wrn> at_host: RX_STOPPED (8)
[00:00:07.882,904] <wrn> at_host: RX_STOPPED (4)
[00:00:07.882,934] <wrn> at_host: RX_STOPPED (8)
[00:00:07.882,995] <wrn> at_host: RX_STOPPED (4)
[00:00:07.883,026] <wrn> at_host: RX_STOPPED (8)
[00:00:07.883,087] <wrn> at_host: RX_STOPPED (4)
[00:00:07.883,117] <wrn> at_host: RX_STOPPED (8)
[00:00:07.883,178] <wrn> at_host: RX_STOPPED (4)
[00:00:07.883,209] <wrn> at_host: RX_STOPPED (8)

After that nRF9160 stops to communicate on serial port (do not react on AT). Serial port is reopened.

In this state I have to power cycle nRF9160.
How to fix that please ?

I am using AT+CPSMS=1,,,"00100001","00000000" for PSM.

After AT#XSLEEP=1 while in +CEREG: 5 and wakeup by GPIO (button on Thingy91) nRF9160 always re-register into EPC open new session and goes through +CEREG: 2.
How to keep session during PSM please and save power for re-register please ?

[SilasV]

HI 

Thanks for your suggestion. On my custom board, I am using P0.05 - RX and P0.06 TX, and I configured the RX pin=5 as wakeup --> CONFIG_SLM_INTERFACE_PIN=5, but that did not help, the modem does not respond on power up (I don't receive Ready response). 

So I am considering a dedicated pin for the wakeup. I will soon get the new version of PCB. 

Thank you

[Stian Røed Hafskjold]

Hi, I just tried waking up using a dummy byte over UART, and I managed to do it successfully while also keeping the connection.

• First you have to set CONFIG_SLM_INTERFACE_PIN to 19, which is the uart0 RX on the thingy91.
• Then in the exit_idle() function add a 1 second delay before slm_at_host_init(), so that the dummy byte finishes transmitting before the at host init. The function should now look like this:
  

  static void exit_idle(struct k_work *work)
  {
  	int err;
  
  	LOG_INF("Exit Idle");
  	gpio_pin_interrupt_configure(gpio_dev, CONFIG_SLM_INTERFACE_PIN,
  				     GPIO_INT_DISABLE);
  	gpio_remove_callback(gpio_dev, &gpio_cb);
  	/* Do the same as nrf_gpio_cfg_default() */
  	gpio_pin_configure(gpio_dev, CONFIG_SLM_INTERFACE_PIN, GPIO_INPUT);
  	/* Restart SLM services */
  	
  	k_sleep(K_MSEC(1000)); // <- ADD THIS LINE
  	
  	err = slm_at_host_init();
  	if (err) {
  		LOG_ERR("Failed to init at_host: %d", err);
  	}
  }

Here are the AT commands I used in the LTE link Monitor:

a
Ready
AT+CFUN=1
OK
AT+CEREG=5
OK
AT+CPSMS=1,"","","10100001","00000000"
OK
AT+CEREG?
+CEREG: 5,5,"0AD3","020EC516",7,,,"00000000","00000110"
OK
AT#XSLEEP=0
a
Ready
Ready
AT+CEREG?
+CEREG: 5,5,"0AD3","020EC516",7,,,"00000000","00000110"
OK

So you can see that I'm waking up with just sending the letter "a", then I get the Ready response, and then you see from the AT+CEREG? that the modem is still connected

I also tried unplugging the USB after AT#XSLEEP=0, and plugging it back in, and it still works, still connected to the network (you have to reconnect to the USB device in the LTE Link Monitor software)

NOTE

I see that you are using AT#XSLEEP=1. This command is shutting down the modem, disconnecting from the network before going to sleep. Use AT#XSLEEP=0 if you want to keep the connection

[SilasV]

Hi Stian

Just for the test sake, I tried this in the prj file: 

# Enable GPIO wakeup if sleep is expected
CONFIG_SLM_GPIO_WAKEUP=y
CONFIG_SLM_INTERFACE_PIN=26

Although my custom board does not use P0.26 pin, this pin is left open on the current version of the nrf9160 PCB. And surprisingly it works!!

when powered up, it does not respond with "ready", but just sending a random character, it responds with "ready", so I believe that after power up, the modem is in sleep mode. Sending character 'a' wakes it up, and then sending regular commands for UDP connection and sending data. After that sending "AT#XSLEEP=1" to put it sleep mode. I tried wake up after 15min, and it worked as expected. 

Is there any time limit to which the sleep mode? I tried wake up after 50min, and it did not respond with 'ready'. In normal application, the sleep period of the device would be between 15min to 30min (user configurable). Would you please let me know if there is any limitation on the sleep period for nRF9160 . 

Thanks you