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~

[akckwang]

Hi Simonr,

The power source is a power supply GW INSTEK GPS-3030D, and yes I connected only this one power source, no usb or battery,
I just call nrf_gpio_cfg_output(xxx), nrf_gpio_pin_set(xxx) to control gpio then measuring voltage by digital multimeter

Thanks~

[akckwang]

Hi Simonr,

I raise the power supply to ~2.4v then gpios working normally,

The manual of nrf52832-dk mentioned this 

" The reverse voltage protection diodes will add a voltage drop to the supply voltage of the circuit. To avoid
this voltage drop, the diodes can be bypassed by shorting one or more solder bridges."

I was set power supply to 1.8v and I didn't wire SB12,
so the voltage became too low to enable nrf52832-dk, I guess...

Whatever I can control gpio with external power source now.

Thanks~

[Simonr]

Glad to hear you figured it out! Yes, it seems reasonable that the voltage drop is what caused the DK to not power up properly when supplied with 1.8V. Let me know if we can close this case or if you have any further questions.

Best regards,

Simon