ncs-serial-mode dtr/ri operation

[thipp]

I am trying to use the Serial Modem Add-On (SM) application with the attached overlay-external-mcu.overlay.
overlay-external-mcu.overlay
When DTR is asserted (active low), the modem stops responding to AT commands, but de-asserting DTR (host-initiated wake-up) does not restore UART communications. 
I see no activity on the RING line.

Also, it seems that if DTR is asserted (active low) or de-asserted (high) immediately after power up that the modem continues to respond normally as if DTR has no effect.So it seems like toggling DTR kills the modem, but just driving it high or low and leaving it there does nothing.

From the migration notes, the DTR and RI gpios are supposed to be controlled by the dtr-gpios/ri-gpios properties.
How do I confirm these are properly configured in the build?
https://docs.nordicsemi.com/bundle/addon-serial_modem-v0.2.0/page/migration_notes.html

Is there some other missing configuration piece needed to match the sequence diagrams in https://docs.nordicsemi.com/bundle/addon-serial_modem-v0.3.0/page/uart_configuration.html

 

[thipp]

Vidar,

This is a custom board with external mcu.  Both the mcu and modem reference the same GND.  The DTR/RING signals are wired per the documented interface setup and the voltage levels match (1.8V).  I will try and enable the  CONFIG_DTR_UART_LOG_LEVEL_DBG to see what it provides.  Is there a way to review generated output files to confirm the DTR and RING pins are configured properly?

[thipp]

Here is my investigation on whether or not the pins are properly configured.
If I go to my root build_mcu_ext configuration, it looks like the sm_ctrl.pin.c SM_DTR_GPIOS is properly defined.


But if I select build_mcu_ext/ncs-serial-modem configuration,  SM_DTR_GPIOS is not properly defined.

If I do a search for ncs_sm_uart, it looks like my build_evk is setup for a dtr_uart, but my build_mcu_ext is not

I am following all the documentation for using the overlay-external-mcu.overlay, what should I expect to see?

[thipp]

FYI, my yellow hightlighting masked the fact when SM_DTR_GPIOS is not properly defined, the highlighted text is grayed out.

[Vidar Berg]

Hello,

You can confirm what is being applied to the build by inspecting the generated zephyr.dts file for your modem app:

Are you using the nrf9151dk as your build target, or have you defined your own board?

[thipp]

Thank you. 
I found my issue. I had somehow created a duplicate overlay-external-mcu.overlay file in the "apps" folder and my build was pointing to it instead of the correct overlay file.

[Vidar Berg]

I’m glad to hear you found the problem. Thank you for reporting back on what the issue was.