Using SWO with nRF52 (redux)

RE: Using SWO with nRF52 (redux)

Igor — Fri, 18 May 2018 14:11:50 GMT

Oh, I missed this. Thank you for your answer.

RE: Using SWO with nRF52 (redux)

Jui-Chou (Rick) Chung — Fri, 18 May 2018 13:29:41 GMT

Hello Igor,

I would like to suggest you check the "pin assignment" for nRF52840 in the inforcenter:

https://infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.nrf52840.ps%2Fpin.html&cp=2_0_0_6_0_0&anchor=qfn48

According to the upon link, the P1.00 has SWO function.

Hope this can do help :)

RE: Using SWO with nRF52 (redux)

Igor — Fri, 18 May 2018 13:18:36 GMT

Jui-Chou (Rick) Chung What about nRF52840? It It uses P0.18 as RESET. To which pin is SWO bound in this case?

RE: Using SWO with nRF52 (redux)

ekrashtan — Fri, 08 Dec 2017 21:41:08 GMT

Thanks, Rick, it works fine. But I have next question - is it possible to route NRF_LOG output to SWO? Actually, I see only UART (needs the extra converter) or RTT (requires a lot of RAM) variants. I put

int __putchar(int ch, FILE * p_file)
{
   ITM_SendChar(ch);
   return ch;
}

to my code and can use printf for output, but it's not enough for me.

RE: Using SWO with nRF52 (redux)

apuret — Thu, 11 Aug 2016 09:13:36 GMT

Tested and approved, thanks Rick ! For my use case, I write 'retarget' functions:

int _write(int file, char *ptr, int len) {
	UNUSED_PARAMETER(file);
	for (int i = 0; i < len; i++)
		ITM_SendChar(ptr[i]);
	return len;
}

int _write_r(struct _reent *r, int file, char *ptr, int len) {
	UNUSED_PARAMETER(r);
	UNUSED_PARAMETER(file);
	for (int i = 0; i < len; i++)
		ITM_SendChar(ptr[i]);
	return len;
}

RE: Using SWO with nRF52 (redux)

Jui-Chou (Rick) Chung — Mon, 30 May 2016 04:31:34 GMT

Hello Jprofit,

The following steps showing how to configure the SWO, hope it can satisfy your question : D

add the additional define "ENABLE_SWO" to the project setting, which will set the nRF52 P0.18 as SWO instead of been a common GPIO
set the TRACECONFIG register for trace port debug interface; the detail can be found in here. If you are using JLink-OB on the PCA10040, the maximum SWO sampling frequencey is 7.5MHz, so it is needed to configure the TRACEPORTSPEED to 4MHz.
Set the trace enable register and trace control register which in the "Instrumentation Trace Macrocell" to turn on the ITM stimulus
call the ITM_SendChar(uint32_t ch) to transmit the character via ITM channel 0, the detail can be found in the /components/toolchain/CMSIS/Include/core_cm4.h

Sample code:

#include <stdint.h>
#include "nrf.h"

int main(void)
{
	// step 2
	NRF_CLOCK->TRACECONFIG = (NRF_CLOCK->TRACECONFIG & ~CLOCK_TRACECONFIG_TRACEPORTSPEED_Msk) |
		(CLOCK_TRACECONFIG_TRACEPORTSPEED_4MHz << CLOCK_TRACECONFIG_TRACEPORTSPEED_Pos);
	// step 3
	ITM->TCR |= 1;
	ITM->TER |= 1;
	uint8_t c = 65;
	while (true)
	{
		// step 4	
		ITM_SendChar(c);
		if( c >= 90){
			c = 65;
		}else{
			c++;
		}
	}
}

After flash the code, execute the JLinkExe and set the SWO speed to 4MHz, then you will see the result on the screen:

~$ JLinkExe -if swd -device nrf52 -speed auto
JLink>connect
JLink>swoview 4000000
Receiving SWO data @ 4000 kHz
Data from stimulus port 0:
--------------------------------------------------------
ABCD...

RE: Using SWO with nRF52 (redux)

Justin — Sat, 07 May 2016 00:57:47 GMT

You might want to use RTT, it is much faster than using SWO www.segger.com/jlink-rtt.html

RE: Using SWO with nRF52 (redux)

jprofit — Fri, 06 May 2016 22:36:17 GMT

Ahhh... I thought RTT was synonymous with SWO. Thanks for the clarification. Do you know if there is an API in the SDK somewhere for using SWO based debug output?

RE: Using SWO with nRF52 (redux)

Justin — Fri, 06 May 2016 22:23:06 GMT

It looks like you're logging to RTT and not SWO, you might want to try JLinkRTTClient after running JLinkGDBServer