I would like to ensure that a particular GPIO pin is disconnected when an nRF52840 is powered up via the initial configuration specified in the DeviceTree board overlay file. I am using nRF Connect SDK v3.2.1 with an nRF52840 Dongle. The pin will be used later as an output, but I must ensure there are no spurious signals on the pin until that time. What is the recommended method of doing this?
Thank you,
Ken
Hi Ken,
The only scenario in high voltage mode where I can see it getting close to 3.5V is if REGOUT0 is configured to 3v3 and you add the +5% worst case accuracy deviation.
Ken58 said:What if back in 2018 for example, REGOUT0 was set permanently with option value 6, the missing value in the list of possible values. Was there an 3V5 option?
3v3 has always been the maximum and our SDK code (both new and old) has been setting the register to 3.0v.
(https://docs.nordicsemi.com/bundle/ps_nrf52840/page/power.html#ariaid-title74)
Ken58 said:I don't know if that matters, but they are missing resistor R7, a 47 ohm series resistor between VBUS and VDDH.
This is interesting. I was not aware of this. Maybe this can explain why you didn't observe the same spike when testing with the DK. The series resistor was added in revision 2.0.0 of the DK.
Also from the "Reference circuitry" chapter of the Product specification:
Ken58 said:Is there any code available in the SDK that would allow me to easily erase the UICR, and then execute code like in board_early_init_hook() to set REGOUT0 to 3V on my 3V5 Dongle?
There isn't any existing code for this unfortunately. But maybe you can read out the register before making any attempts on this.
#include <soc.h>
...
LOG_INF("NRF_UICR->REGOUT0: %d", NRF_UICR->REGOUT0);
Best regards,
Vidar
The nrf52840Dongle/nrf52840 board target enables the USB by default so you shouldn't have to change anything to make this work. To test you can try the "Hello World" sample and print something in a loop.
Relevant devicetree entries
