Connect UART to J-Link to access OpenThread CLI with nRF Connect SDK

[GPereira]

My team is trying to acess OpenThread CLI over UART0 with the nRF Connect SDK OpenThread CLI sample with our custom board.

We have tested with a Nordic's nRF52840 DevKit and it works perfectly, however with our custom board using a J-Link which doesn't have RTS and CTS pins it isn't working.

We already tried the blinky example so we have ensured ourr power supply is OK, but we suspect that we need to disable UART hardware flow control in order to use a regular JLink, is this correct? In that case what configurations do we need?

[Edvin]

We already tried the blinky example so we have ensured ourr power supply is OK

 I am not sure exactly how this works in NCS (nRF Connect SDK), but it is a common issue in the nRF5 SDK. Does your custom board have an external LFXTAL? If not, is the application aware of this? 

BR,
Edvin

[Edvin]

Actually, I don't think that openthread is dependent on the LFXTAL. If you want to change something on the UART, you need to rebuild the openthread stack. Please check how to rebuild it, and modify the UART before you build it. Make sure to use the same github tag as the SDK is using. It is mentioned in 4.1.0\external\openthread\project\readme.txt.

Best regards,

Edvin

[GPereira]

I am describing the UART interface on NCS using device tree. I am declaring my UART pins and I would expect to access zephyr console from that interface. We can put openthread to the side for now since openthread CLI will be on top of that using the ot command.

[Edvin]

How exactly did you change this in your device tree? 

[GPereira]

&uart0 {

compatible = "nordic,nrf-uart";

status = "okay";

current-speed = <115200>;

tx-pin = <6>;

rx-pin = <8>;

};

[Edvin]

Ok, I guess you tried this in another example, and it worked? I suspect that it is a bit different in the Openthread examples, because the UART is more heavily weaved into the openthread module. I will have to look more into this. 

First: Can you confirm that this works without any issues in a non-thread examples in NCS (nRF Connect SDK)? E.g a hello-world or blinky example, where you don't use flow control on the custom board? Just to check whether this is opnethread related at all.

[GPereira]

No it does not work with any sample. Only works on nRF52840 DK but on my device I am not able to use hardware flow control. Any solution? I only need that connection for debugging purposes.