Serial LTE Modem app in NCS main - glitch on TX before INDICATE

[Michal Mühlpachr]

Hi, 

NCS main, nRF9160 DK

git log -n 1 --oneline
4f916da03 (HEAD -> main, origin/main, origin/HEAD) west.yml: rebase OSS trees

SLM prj.conf changes:

CONFIG_SLM_START_SLEEP=y

CONFIG_SLM_WAKEUP_PIN=6

CONFIG_SLM_INDICATE_PIN=2

CONFIG_NRF_MODEM_LIB_TRACE_ENABLED=y

There is unexpected glitch on TX just beforfe INDICATE is active:

Regards,

Michal

[Michal Mühlpachr]

Hi Markus,

Albrecht Markus Schellenberger said:

I’m not sure if I fully understand this. I assume that the indicate pin was triggered here which causes the glitch, right? 

Fullscreen

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2

52.70 <INDICATE transition> -> High

52.78 <INDICATE transition> -> Low

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

52.70 <INDICATE transition> -> High 
52.78 <INDICATE transition> -> Low 

How was the pin triggered? It doesn’t seem to me that the SLM application did it itself? 

Regards, 

Markus 

Yes, INDICATE transition marks where INDICATE pin was activated by SLM.

Yes, SLM do it itself because of CONFIG_SLM_INDICATE_PIN=2 setting in prj.conf.

Reason for SLM to raise INDICATE is "+CSCON: 0" URC during #XSLEEP=2.

INDICATE pin is way for SLM how to make host know: hey, there are some bytes in AT UART TX buffer who can not be transmited because UART is in sleep. So host can then wakeup SLM by WAKEUP pin and let him to transmit data in UART TX buffer after "Ready" URC.

Regards,
Michal