Application does not start without debugger connected

RE: Application does not start without debugger connected

bloobird0 — Tue, 06 Dec 2016 11:10:33 GMT

Thanks butch for your time. After investigation with the oscilloscope I found that the firmware runs on the development board, not on the prototype board, the difference is the lack of external oscillator which is used for the stack initialization. Because this topic is different from this one, I close it. Anyway, my problem is not related to the availability of a debugger anymore, I can reproduce the same errors I had.

RE: Application does not start without debugger connected

butch — Mon, 28 Nov 2016 14:15:33 GMT

I would study the sw and hw configuration of the SWD pins (CLK and DIO) on the custom board. I think any debugger can reset (or hold the mcu in reset) by some signal on those pins. For example, maybe the pins must have a pullup resistor so they don't float? (I don't really know, I am just guessing that in your case without a debugger connected, the pins might be holding mcu in reset.)

I assume you have not changed the standard POR reset interrupt vector and the other standard C startup code including SD startup?

BTW, I don't think you should answer, but should comment, so that others don't see that it has been "answered" and skip reading your thread.

RE: Application does not start without debugger connected

bloobird0 — Mon, 28 Nov 2016 11:14:23 GMT

Hello butch, you're right without the debugger connected, RTT viewer can't display anyting ;-)

I've been further and I can't identify where I should look at:

I updated the firmware to continuously toggle a pin so that I can see the device running with the oscilloscope. The first thing that the firmware does is toggle the pin so I should be able to see it toggling even if a restart occurs soon after power on.
I flash the custom board from Keil or nRF Go Studio through the nRF52DK. After the flash, the pin does not toggle.
it starts toggling only when I start RTT Viewer (nRF52DK still connected). I output the RESETREAS value which is 0x0004: software reset. I guess that RTT Viewer writes in the RESET register. Am I right?

Now I disconnect the custom board from the nRF52DK. I apply a power cycle. The pin is not toggling. I expected a power on reset to happen. I plug the nRF52DK debugger: the pin is not toggling. I start RTT viewer: the pin is toggling.

I understand that the custom board remains in a reset state until the RTT viewer sets a software reset.

Do I have to initialize anything in the firmware so that it starts when power is applied?

The reset pin is not used.

RE: Application does not start without debugger connected

butch — Sat, 19 Nov 2016 23:00:38 GMT

Maybe I am confused but: doesn't the RTT viewer communicate via SWDIO/SWCLK? So how could it display debug messages if that is disconnected? Yes, the fact that it is not advertising is strange. Is there an LED you can flash? How do you handle faults/exceptions? What is the power supply when flashing versus your other configuration?