GSM Modem Sample Project on nRF 5340 App

Question

Hi. I am trying to get the gsm modem sample project to work with an nRF 5340 app and a Nimbelink LTE modem, NL-SW-LTE-TC4NAG. The only change I made to the project was to add a new file in the boards directory for the 5340. The nrf5340dk_nrf5340_cpuapp.overlay file is below. 
 The problem is that `uart_dev` is null. The console output I get is below. 
 I'm not sure if this is a configuration issue or if the modem is not up when `device_get_binding()` is called. What am I missing? 
 sample_gsm_ppp: Board 'nrf5340dk_nrf5340_cpuapp' APN 'internet' UART 'UART_1' device (nil) (modem_gsm) 
 &uart0 {
 compatible = "zephyr,gsm-ppp"; // also tried: gsm_ppp,MODEM_GSM_PPP,modem_gsm
 label = "UART_1";
	status = "okay";
	current-speed = <115200>;

	gsm: gsm-modem {
 compatible = "zephyr,gsm-ppp";
 label = "gsm_ppp";
	};
};

Albrecht Markus Schellenberger · Accepted Answer

Hello,

code-magic said:
Is this correct for the pin number for TX: `tx-pin = <3>;`?

In your case, the .overlay should look like this:

&uart0 {
    status = "okay";
    tx-pin = <3>;
	rx-pin = <8>;
	rts-pin = <2>;
	cts-pin = <7>;
};

code-magic said:
The modem will be ran from the net core on non standard pins for TX, RX, RTS, & CTS. Given this, do I need to only need to set the pins in my overlay file for UART 0. Or will setting this for UART1 on net core be ok?

Please be aware that the app core has to give the net core permission for each pin it wants to use, as illustrated in the nRF5340: Empty firmware for application core sample. I’m not quite sure how sufficient it will work having the GSM modem connected to the net core, as it in general is not designed for this kind of usage. So my recommendation would be to use the app core instead.

Regards,

Markus

GSM Modem Sample Project on nRF 5340 App

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