Serial LTE Modem app in NCS main has unexpected power consumption after #XSLEEP=2

Hi,

Here are the functions called when going to sleep:

https://github.com/nrfconnect/sdk-nrf/blob/v1.9.1/applications/serial_lte_modem/src/slm_at_commands.c#L132-L134

The UART is disabled, SLM (and deps) are uninit'ed, and GPIOs are set to an idle level for the UART that is chosen for the SLM interface.

However:

CONFIG_NRF_MODEM_LIB_TRACE_ENABLED=y

This is not handled by SLM. You need to disable uart1, and set the rxd/txd gpio's to an idle level, similar to what is done in SLM, for instance by calling nrf_gpio_cfg_default() on those pins.

Could you try to either disable tracing, or set those to the default (ie. reset value) state?

Kind regards,

Håkon

With disabled tracing sleep power consuption is more unstable without obvious reason:

[PPK2] Found PPK2 at COM9
[PPK2] DUT Powered, Measurement started
0.16 <RESET> Mon May 23 02:41:30 2022
1.01 [PPK2] 100k/s AVG 3.99 mA Max 44.3 mA
2.03 [PPK2] 100k/s AVG 1.57 mA Max 26.3 mA
3.01 [PPK2] 100k/s AVG 0.008mA Max 0.711mA
4.03 [PPK2] 100k/s AVG 0.011mA Max 0.711mA
5.04 [PPK2] 100k/s AVG 0.012mA Max 0.711mA
6.02 [PPK2] 100k/s AVG 0.007mA Max 0.711mA
7.01 [PPK2] 100k/s AVG 0.016mA Max 0.711mA
7.11 <WAKEUP>
8.04 [PPK2] 100k/s AVG 0.955mA Max 20.5 mA
8.47 [RX] Ready
9.01 [PPK2] 100k/s AVG 2.23 mA Max 33.4 mA
10.02 [PPK2] 100k/s AVG 0.698mA Max 14.6 mA
11.02 [PPK2] 100k/s AVG 0.693mA Max 16.9 mA
12.03 [PPK2] 100k/s AVG 0.695mA Max 16.1 mA
13.03 [PPK2] 100k/s AVG 0.697mA Max 16.0 mA
13.62 [TX] AT#XSLEEP=2
13.62 [RX] OK
14.01 [PPK2] 100k/s AVG 0.509mA Max 16.5 mA
15.02 [PPK2] 100k/s AVG 0.008mA Max 0.711mA
16.03 [PPK2] 100k/s AVG 0.009mA Max 0.711mA
17.03 [PPK2] 100k/s AVG 0.005mA Max 0.711mA
18.03 [PPK2] 100k/s AVG 0.009mA Max 0.711mA
19.01 [PPK2] 100k/s AVG 0.008mA Max 0.711mA
20.02 [PPK2] 100k/s AVG 0.007mA Max 0.711mA
21.02 [PPK2] 100k/s AVG 0.010mA Max 0.711mA
22.02 [PPK2] 100k/s AVG 0.007mA Max 0.711mA
23.03 [PPK2] 100k/s AVG 0.007mA Max 0.711mA
24.05 [PPK2] 100k/s AVG 0.008mA Max 0.711mA
25.01 [PPK2] 100k/s AVG 0.022mA Max 21.0 mA
26.04 [PPK2] 100k/s AVG 0.030mA Max 16.5 mA
27.04 [PPK2] 100k/s AVG 0.024mA Max 0.711mA
28.02 [PPK2] 100k/s AVG 0.024mA Max 0.711mA
29.02 [PPK2] 100k/s AVG 0.026mA Max 0.711mA
30.04 [PPK2] 100k/s AVG 0.023mA Max 0.711mA
31.02 [PPK2] 100k/s AVG 0.022mA Max 0.711mA
32.01 [PPK2] 100k/s AVG 0.023mA Max 0.711mA
33.03 [PPK2] 100k/s AVG 0.025mA Max 0.711mA

With disabled tracing sleep power consuption is more unstable without obvious reason:

[PPK2] Found PPK2 at COM9
[PPK2] DUT Powered, Measurement started
0.16 <RESET> Mon May 23 02:41:30 2022
1.01 [PPK2] 100k/s AVG 3.99 mA Max 44.3 mA
2.03 [PPK2] 100k/s AVG 1.57 mA Max 26.3 mA
3.01 [PPK2] 100k/s AVG 0.008mA Max 0.711mA
4.03 [PPK2] 100k/s AVG 0.011mA Max 0.711mA
5.04 [PPK2] 100k/s AVG 0.012mA Max 0.711mA
6.02 [PPK2] 100k/s AVG 0.007mA Max 0.711mA
7.01 [PPK2] 100k/s AVG 0.016mA Max 0.711mA
7.11 <WAKEUP>
8.04 [PPK2] 100k/s AVG 0.955mA Max 20.5 mA
8.47 [RX] Ready
9.01 [PPK2] 100k/s AVG 2.23 mA Max 33.4 mA
10.02 [PPK2] 100k/s AVG 0.698mA Max 14.6 mA
11.02 [PPK2] 100k/s AVG 0.693mA Max 16.9 mA
12.03 [PPK2] 100k/s AVG 0.695mA Max 16.1 mA
13.03 [PPK2] 100k/s AVG 0.697mA Max 16.0 mA
13.62 [TX] AT#XSLEEP=2
13.62 [RX] OK
14.01 [PPK2] 100k/s AVG 0.509mA Max 16.5 mA
15.02 [PPK2] 100k/s AVG 0.008mA Max 0.711mA
16.03 [PPK2] 100k/s AVG 0.009mA Max 0.711mA
17.03 [PPK2] 100k/s AVG 0.005mA Max 0.711mA
18.03 [PPK2] 100k/s AVG 0.009mA Max 0.711mA
19.01 [PPK2] 100k/s AVG 0.008mA Max 0.711mA
20.02 [PPK2] 100k/s AVG 0.007mA Max 0.711mA
21.02 [PPK2] 100k/s AVG 0.010mA Max 0.711mA
22.02 [PPK2] 100k/s AVG 0.007mA Max 0.711mA
23.03 [PPK2] 100k/s AVG 0.007mA Max 0.711mA
24.05 [PPK2] 100k/s AVG 0.008mA Max 0.711mA
25.01 [PPK2] 100k/s AVG 0.022mA Max 21.0 mA
26.04 [PPK2] 100k/s AVG 0.030mA Max 16.5 mA
27.04 [PPK2] 100k/s AVG 0.024mA Max 0.711mA
28.02 [PPK2] 100k/s AVG 0.024mA Max 0.711mA
29.02 [PPK2] 100k/s AVG 0.026mA Max 0.711mA
30.04 [PPK2] 100k/s AVG 0.023mA Max 0.711mA
31.02 [PPK2] 100k/s AVG 0.022mA Max 0.711mA
32.01 [PPK2] 100k/s AVG 0.023mA Max 0.711mA
33.03 [PPK2] 100k/s AVG 0.025mA Max 0.711mA

Hi,

I think I've found what is floating. Are you connecting this signal to an external host controller?

CONFIG_SLM_INDICATE_PIN=2

When starting directly in sleep, this pin is floating, with configuration input buffer disconnected.

This means that the nRF will not draw extra current, but any external logic connected on this pin can potentially draw added current.

Kind regards,

Håkon

Hi,

I am using 12k pull-down on INDICATE pin now.

I do not uderstand, why power consuption after RESET is stable but higher and unstable after #XSLEEP=2.

Regards,
Michal

Hi Michal,

I am not sure how you're testing this, but I'm unable to reproduce the behavior that you see.

Here's a sleep period, wake-up condition, and issuing "AT#XSLEEP=2" after wakeup:

Could you explain your test-setup more in-depth? Is this a stock SLM application, running on the nRF9160-DK with no additional sensors?

Kind regards,

Håkon

Hi Håkon,

I described test setup in https://docs.google.com/document/d/1HuWBlC9k0IS1NcfX7aGUEJqAxwaqZV2D8SHFDCM0CXs/edit?usp=sharing

It is stock SLM application, running on the nRF9160-DK with no additional sensors.

I do not know, why your nRF9160 power consuption during #XSLEEP=2 is so high, ~42uA

Regards,

Michal

Hi,

Thank you for providing a detailed setup description.

Is there a specific reason why you're using an external usb/uart converter? Have you tried disconnecting this to see if that is the source of the added consumption? If the voltage levels are not equal on these two setups, you will get leakage.

I am unable to reproduce the issue that you're seeing, unfortunately.

Could you try to add a gpio disconnect loop between these two lines?

https://github.com/nrfconnect/sdk-nrf/blob/v1.9.1/applications/serial_lte_modem/src/slm_at_commands.c#L135-L136

	/* For testing purposes */
	for (int i= 0; i < 32; i ++) {
		nrf_gpio_cfg_default(i);
	}

Kind regards,

Håkon