State of GPIO pins during flash and reset/reboot

[Dan]

Device: NRF5340; NRF Connect SDK 2.5.0.

We have a 12V DC motor connected to NRF5340 GPIO P1.13 (direction) and P1.11 (speed: 0 = stop; 1 = full speed). Whenever we flash our device or reset it (reset pin), the motor turns until our initialization code stops it. How can we get it to not turn during flash and reboot?

When our code runs, in it's init function,  it configures the relevant pins using gpio_pin_configure(gpio_1, pin_number, GPIO_PULL_DOWN) and the motor stops turning, but we can't have the motor turning during a reflash/OTA/reset. 

There are related tickets asking about GPIO state during reset/reboot but it's unclear whether the pins are set to high impedance inputs with no pull up/pull down or can be set to low.
https://devzone.nordicsemi.com/f/nordic-q-a/36508/nrf52840-pin-state-during-reset 

 https://devzone.nordicsemi.com/f/nordic-q-a/67558/twi-sda-scl-held-low-during-reset-when-using-twis/276873  

Appreciate any help or guidance you can offer as to how we may be able to keep these GPIO pins at low during flash or reset. Thanks! Dan.

[Håkon Alseth]

Hi,

 

When the device is actively in RESET mode, the GPIO pins are seen as undefined. Once the nRF is booted up, the pins are by-default configured as input with pin-buffer disconnected, until the firmware itself re-configures the GPIOs in question.

 

I would recommend that you use external pull-resistors in this case.

 

Kind regards,

Håkon

[Dan]

Sounds good - we were able to to hack a fix through the hardware.

[Håkon Alseth]

Glad to hear!

Let us know if there's anything else that pops up. Hope you have a wonderful day!

 

Kind regards,

Håkon