Does nRFgo Studio 1.20.0 "release" the nRF51822 SWDIO pin to be used as a chip reset?

[David Fritsch]

I have a Rev3 nRF51822 chip (CFACA00) on a custom board (no external pull resistors on SWDIO or SWCLK), and I am using nRFgo Studio 1.20.0.2 to program SD 8.0.0 and my Nordic application.

The hardware/firmware relies on the nReset pin to reset the Nordic chip. The main MCU and the Nordic are both powered off of the battery, and there is currently no way to perform a true POR of the Nordic (short or disconnecting the battery).

It appears that after programming the Nordic with 1.20.0, that the Nordic reset is not happening upon my main MCU application reset/start-up. After programming, if I disconnect the battery, or if I manually enable the pin reset while in debug mode with a JLinkExe batch/script (writing the NRF_POWER->RESET register (at 0x40000544, and toggling the reset pin), then Nordic nReset pin is active as a reset pin, and my application successfully resets the Nordic on start-up.

[Hung Bui]

@David Fritsch: It was the fact that nRFGo Studio will leave the chip in debug mode after programming (or after reading chip info). To be able to do a pin reset when in debug mode you must set the RESET register to 1 as you did with JlinkExe.

If you don't want to use nrfjprog or JlinkExe to do that manually, you can enable it in the code. Just add NRF_POWER->RESET =1; in your code, you should be able to do pin reset after programming.

[David Fritsch]

Thanks Hung! This made a difference for me. After adding NRF_POWER>RESET=1 to my application code (first line in main()), my Nordic chip reset works both after debugging in Keil, and after programming with nRGgo Studio 1.20.0.