nrf52832-dk(PCA10040) external power and gpio

[akckwang]

Hi,

I have a nrf52832 dk(pca10040 1.2.1), use gpio P0.29, P0.30, P0.31 to connect some external device,

external device working voltage is maximum 2.2v,
so I connect external power 1.8v to nrf52832-dk P21,

Then the gpios of nrf52832-dk not working, I can't set them to output by

nrf_gpio_cfg_output(pin);nrf_gpio_pin_set(pin);

I tried other pins, and it seems only P0.21/05/06/07/08 can be controlled when using external power,

Why gpios can't be controlled?
do I miss some additional configuration for gpio with external power?

Thanks~

[Simonr]

Hi

What kind of power source is this exactly, and have you connected it correctly to P21? Please note that you should only connect one power source at the time. The GPIOs you say are working are the reset pin (P0.21), and the default GPIOs used for UART (P0.05-P0.08). How exactly are you "controlling" these pins? 

Best regards,

Simon