How to achieve lower shutdown current with Serial LTE Modem?

RE: How to achieve lower shutdown current with Serial LTE Modem?

Anthony Ambuehl — Wed, 16 Jun 2021 18:44:30 GMT

Well I guess, that keeps me in business.

RE: How to achieve lower shutdown current with Serial LTE Modem?

Øyvind — Wed, 16 Jun 2021 08:58:27 GMT

Yes, we are aware of this and this was a choice our developers made. That said, customers are free to implement wake on UART by them selves. The RX pin can be used as a GPIO when UART is not enabled.

Please note that the external device must be configured correctly, so that it does not unintentionally wake device.

RE: How to achieve lower shutdown current with Serial LTE Modem?

Anthony Ambuehl — Tue, 15 Jun 2021 15:43:29 GMT

Requiring an additional GPIO to wake the device seems inefficient, why not just utilize the serial pins to wake the device ? Its a pretty common method, and gives a much more stream-lined solution without consuming another pin from the controlling MCU.

RE: How to achieve lower shutdown current with Serial LTE Modem?

Øyvind — Tue, 15 Jun 2021 08:00:09 GMT

Hi,

[quote user="anthony.asterisk"]According to the docs:[/quote]

The documentation was not correct. Please see latest documentation for update/fix: https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/applications/serial_lte_modem/doc/Generic_AT_commands.html#power-saving-xsleep

In the case of XSLEEP=2, one must use GPIO to wake up.

Let me know how that works for you.

Kind regards,
Øyvind

RE: How to achieve lower shutdown current with Serial LTE Modem?

Anthony Ambuehl — Fri, 11 Jun 2021 17:27:09 GMT

Yes I tried it yesterday afternoon, I did get current down to 10 uA with #XSLEEP.

I noticed the documentation for #XSLEEP does not match the implementation discussed here in devzone.

According to the docs:

https://developer.nordicsemi.com/nRF_Connect_SDK/doc/1.5.1/nrf/applications/serial_lte_modem/doc/Generic_AT_commands.html#power-saving-xsleep

The parameter passed with #XSLEEP

should switch between these 2 modes:

0 - Enter Idle. You can also use the syntax AT#XSLEEP.
1 - Enter Sleep.

In case of Idle, it will exit by sending data over UART.
In case of Sleep, it will wake up by GPIO or reset.

However in this devzone thread a different behavior is described:

https://devzone.nordicsemi.com/f/nordic-q-a/69178/thingy-91-serial-lte-modem-psm/283514#283514

Stian Røed Hafskjold said:

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

Also from my testing with #XSLEEP command, #XSLEEP=0 does not wake from UART activity as described in the documentation.

RE: How to achieve lower shutdown current with Serial LTE Modem?

Øyvind — Fri, 11 Jun 2021 11:45:06 GMT

Hello,

Have you tried with the SLM proprietary AT command #XSLEEP?

Kind regards,
Øyvind