Not able to set P.021 to 0 V

[antoniov]

Hello,

for my project, I am using the module BT832A (from Fanstel) that implements the nrf52810. I am using the pin P.021 to drive a switch. The problem is that when I set the pin to 0, I read about 30 mV instead of 0V. Do you think it is a hardware issue (maybe from the module itself)?

Any suggestions to solve the problem?

This is the way I have configured it

#define PWR_FLEX  21 

.
.
.

static void flex_board_init(void)
{
    nrf_gpio_cfg_output(PWR_FLEX);
    nrf_gpio_pin_set(PWR_FLEX);
}

[Kenneth]

It's worth mentioning that the P0.21 may be configured to be used as a pin reset:

https://infocenter.nordicsemi.com/topic/ps_nrf52810/pin.html?cp=3_3_0_6_0

So make sure there is no specific pull on the pin on the module and/or that you have defined CONFIG_GPIO_AS_PINRESET which will enable pin reset in system_nrf52810.c

[antoniov]

Hi Kenneth,

I am aware of that, and I have removed CONFIG_GPIO_AS_PINRESET from the preprocessor (I am using Seggerer Embedded Studio), but I still get 38 mV.

I will try to open the module to check inside.

[Kenneth]

If you don't configure the pin, have you tried to connect a multimeter to P0.21 and measure the current (if any) from P0.21 to VDD and P0.21 to GND. Then you should get good indication if there is any pull active on the pin by ohms law (R = VDD / I).

Best regards,
Kenneth

[antoniov]

Do you mean leaving the pin unconfigured in my firmware and take the measurement?

[antoniov]

Hi Kenneth,

I just followed your suggestion. With the pin not configured, I read 2.86 V at the output and I get 286 uA when I measure the current from P.021 to GND, meaning R= 10k.

I have also opened the module and I found this:

Do you think there is a workaround to solve the problem or I am obliged to choose another pin to get 0V ?

[Kenneth]

Seems they have added a pull up and capacitor on the pin, likely to make it more "robust" as a reset pin. I suggest to use a different pin.

Best regards,
Kenneth