nrf_gpio_pin_set() causes reset

[Eliot Stock]

I have a modem connected to some pins on an nRF51822 on a custom board. Two pins on the modem are active low. One is a reset pin, the other a VCC control. I want these pins on the Nordic configured as output but I want them high immediately, because at this point I'm not powering up the modem, just init()ing my pins. I don't see any way to set an initial state of the pin at the same instant as configuring it as output (despite the comment in nrf_gpio.h L125), so I simply set them high right after configuring them as output.

nrf_gpio_cfg_output(PIN_SF_RESET);
nrf_gpio_pin_set(PIN_SF_RESET);

nrf_gpio_cfg_output(PIN_SF_VCC_ON);
nrf_gpio_pin_set(PIN_SF_VCC_ON); // This causes a reset!

That last call to nrf_gpio_pin_set() will reset the micro about 80% of the time. This is with the SD enabled and I've just started advertising, in case that makes any difference. I'm on SDK 8.0.0. I've tried this on two identical prototype boards and the same thing happens, so it's not a hardware fault on one board.

What might cause this and how can I avoid it?

[Nguyen Hoan Hoang]

Looks like hardware issue. If that pin is not connected, does is reset as well ? What happen when that pin turns on ? I guest it switches power on something. May be you could check to see if it affects the power of the nRF chip. If the power get pulled bellow the threshold it will cause a reset.

[Susheel Nuguru]

most likely there is some APP_ERROR_CHECK failure somewhere else, the default behavior for this is a soft reset.

[RK]

Since that macro does nothing but set a bit in the output register I can see no way that could actually be the cause of a reset, unless PIN_SF_VCC_ON is 26 or 27.

I think you must be failing somewhere else. Start in the hardfault handler, are you going in there, where did you come from? If you reset, what's the reset reason (read it out of the register).

(note: you can set a pin high as soon as you make it an output by setting it high first then making it an output, although that has nothing at all to do with your issue).

[Eliot Stock]

You're right, it had nothing to do with the GPIO stuff. It was an assert in the soft device cause by starting to advertise and then doing stuff right after that.

[Spirit]

@Eliot Stock Where exactly did you have a source of your problem? I have the same issue, but I can't resolve it -> nrf_gpio_pin_set cause a reset :(