No UART output from Printf()

RE: No UART output from Printf()

RodWatt — Sat, 22 Aug 2020 11:26:25 GMT

Hi Martin,

I got this working by adding the following line to the prj.conf f.le.

CONFIG_UART_CONSOLE=y

Im now seeing the printf() as expected.

...

RE: No UART output from Printf()

RodWatt — Wed, 19 Aug 2020 22:41:52 GMT

Hi Martin,

No, it doesn't seem to make any difference.

My overlay file is as follows

&uart0 {
//  compatible = "nordic,nrf-uarte";
  compatible = "nordic,nrf-uart"; 
  status = "okay";  
  current-speed = <115200>;
  tx-pin = <29>;
  rx-pin = <31>;
//  rts-pin = <22>;
//  cts-pin = <17>;
};

and my prj.conf file is

CONFIG_STDOUT_CONSOLE=y
CONFIG_SHELL=y

I see this

with CONFIG_SHELL=y not set, its a black screen

RE: No UART output from Printf()

RodWatt — Tue, 18 Aug 2020 14:04:13 GMT

Hi Martin,

Unfortunately I have managed to brick it, so I cant try it. I have opened a separate ticket here

https://devzone.nordicsemi.com/f/nordic-q-a/64921/nrf52840-dongle-bricked-after-programming

Rod

RE: No UART output from Printf()

Martin Lesund — Tue, 18 Aug 2020 13:56:43 GMT

Hi Rod,
Do you see any difference in behavior if you use:

 compatible = "nordic,nrf-uart";

RE: No UART output from Printf()

RodWatt — Tue, 18 Aug 2020 13:28:56 GMT

Hi Martin,

Initially I did not have the shell enabled and was just running the Hello World sample as normal. I only enabled the shell command to prove that I have set up the UART correctly and that the adapter was working.

Rod

RE: No UART output from Printf()

Martin Lesund — Tue, 18 Aug 2020 13:25:51 GMT

I do not think that you should need to enable "shell" when running this sample.
Printk will print out on the CONSOLE which is default enabled when running on the Dongle.

So the only thing you should do is to run the sample unmodified with .overlay file to change the UART pins

RE: No UART output from Printf()

RodWatt — Mon, 17 Aug 2020 12:38:42 GMT

Hi Martin,

I don't think thats it. I have used this before without flow control to save on the pin count.

Rod

RE: No UART output from Printf()

Martin Lesund — Mon, 17 Aug 2020 12:35:12 GMT

Hi Rod,

I think the issue is that you have not enabled flow control.

Please enable that in prj.conf.

RE: No UART output from Printf()

RodWatt — Mon, 17 Aug 2020 08:28:09 GMT

Hi Martin,

I have tried switching the RX and TX lines and I have verified the adapter works on other boards. Surely if there was a hardware problem with a faulty adapter or RX/TX swapped, the shell wouldn't work? As you will see above, I am able to both transmit and receive via the shell which makes me think the hardware is OK? Or am I missing something?

Rod

RE: No UART output from Printf()

Martin Lesund — Mon, 17 Aug 2020 07:19:30 GMT

Hi Rod,

Sorry, there was a typo. I've changed the post so it is changed to the correct name: "nrf52840dongle_nrf52840.overlay".
Verify the tx and rx lines are correct.

Usually the issue could actually be having the tx/rx lines switched.

Please also verify that the FTDI adapter works on another known device, so we can confirm that the adapter is not the issue.

RE: No UART output from Printf()

RodWatt — Tue, 11 Aug 2020 13:55:44 GMT

Hi Martin,

Yes, I renamed the overlay file. Please can you confirm the name, I think you have typo above, I assume it should be nrf52840dongle_nrf52840.overlay and not nrf52840dongle_nrf5240.overlay as above?

I don't have an LA but the FTDI adapter has LEDS which flash when data is passing though. It lights when I have the shell enabled, but not when shell is disabled.

I guess my overall file must be correct or I would not be able to transmit and received over the shell?

Rod

RE: No UART output from Printf()

Martin Lesund — Tue, 11 Aug 2020 13:46:57 GMT

Hi Rod,
Could you please connect a logic analyzer to the pins to actually check if it's sending out anything.

Did you name the overlay file "nrf52840dongle_nrf52840.overlay"?
If not the UART0 may still be the default option:

&uart0 {
	compatible = "nordic,nrf-uarte";
	status = "okay";
	current-speed = <115200>;
	tx-pin = <20>;
	rx-pin = <24>;
	rts-pin = <17>;
	cts-pin = <22>;
};