How to Map UARTE to physical pins?

RE: How to Map UARTE to physical pins?

Carl Richard — Tue, 29 Sep 2020 08:35:44 GMT

Good to hear! You got it right!

It was my pleasure.

Best regards,
Carl Richard

RE: How to Map UARTE to physical pins?

Learner — Mon, 28 Sep 2020 15:42:57 GMT

Thank you Carl,

I have read the OPS_v0.6.1 again and the penny has finally dropped 💡. I can now see how the PSEL.RXD, PSEL.CTS, PSEL.RTS, and PSEL.TXD can be used to map the different signals (RXD, CTS...), to physical pins.

Thank you for being patient with me.

Kind regards

Mohamed

RE: How to Map UARTE to physical pins?

Carl Richard — Mon, 28 Sep 2020 14:07:33 GMT

Hi again!

It's fine! This happens in the driver, <sdk_root>\zephyr\drivers\serial\uart_nrfx_uarte.c, where the Devicetree(DT) configuration is applied to the UART instance. We do not have any examples on using the registers directly, unfortunately.

Best regards,
Carl Richard

RE: How to Map UARTE to physical pins?

Learner — Mon, 28 Sep 2020 12:05:50 GMT

Hi Carl,

I am sorry to be a pain but I still cannot see how you can use the registers PSEL.RXD, PSEL.CTS, PSEL.RTS, and PSEL.TXD to map the different signals (RXD, CTS...), to physical pins.

Please can you give an example on how you would use these registers to map RXD, CTS,... signals to physical pins?

Kind regards

Mohamed

RE: How to Map UARTE to physical pins?

Carl Richard — Mon, 28 Sep 2020 11:58:52 GMT

Hi again, Mohamed.

It is not explained explicitly in the tutorial, but it does show how the .overlay files are translated into #defines which in turn are used by the drivers(where the registers you mention are set). You can access the registers directly as well, as hinted to by our documentation. However, I recommend using the .overlay files, as mentioned.

Best of luck,
Carl Richard

RE: How to Map UARTE to physical pins?

Learner — Mon, 28 Sep 2020 11:25:28 GMT

Thank you Carl for your prompt response.

I have gone through the tutorial. It covers the Device Tree concept in section 1.4 but nothing on how to use the registers PSEL.RXD, PSEL.CTS, PSEL.RTS, and PSEL.TXD to map the different signals (RXD, CTS...), to physical pins.

I, however, do understand how to use the .overlay file to map the different signals (RXD, CTS...), to physical pins as you explained in your previous reply.

Kind regards

Mohamed

RE: How to Map UARTE to physical pins?

Carl Richard — Mon, 28 Sep 2020 10:38:02 GMT

Hello again!

Good to hear!

These registers are configured through Zephyr's Devicetree overlays. I suggest that your read chapter 1.4 The Device Tree from part 2 of our nRF Connect SDK tutorial, where these concepts are well explained!

Best regards,
Carl Richard

RE: How to Map UARTE to physical pins?

Learner — Mon, 28 Sep 2020 08:50:41 GMT

Thank you Carl.

It is now clear to me how to go about it.

So, what is meant by the following description I read in the user manual OPS_v0.6.1, section 7.38.8?

7.38.8 Pin configuration
The different signals RXD, CTS (Clear To Send, active low), RTS (Request To Send, active low), and TXD
associated with the UARTE are mapped to physical pins according to the configuration specified in the
PSEL.RXD, PSEL.CTS, PSEL.RTS, and PSEL.TXD registers respectively.

Thank you again.

RE: How to Map UARTE to physical pins?

Carl Richard — Mon, 28 Sep 2020 08:12:48 GMT

Hello!

When mapping physical pins in Zephyr you can use overlay files. For example, if you want to map the UARTE of the application processor of the nRF5340 on the PDK do the following:
- Make a file in your project directory called: nrf5340pdk_nrf5340_cpuapp.overlay
- Fill it with the following code:

&uart0 {
	compatible = "nordic,nrf-uarte";
	status = "okay";
	tx-pin = < 0x14 >;
	rx-pin = < 0x16 >;
	rts-pin = < 0x13 >;
	cts-pin = < 0x15 >;
};

You can see how it's done for the nRF52840 DK here and you can read more about the Devicetree overlays here.

Hope this helps!

Best regards,
Carl Richard