nRF52832: Power OFF/Reset with UART connected

[Marco]

Hi,

I wanted to know if the UART pins can cause any issues if kept connected to usb (Rx/Tx pins stable to 3.3V) and directly to the GPIOs of the nRF52, while performing a soft-reset or switching OFF and then ON the device.

I have a sensor (ADXL362) connected to nRF52 via SPI and when I restart the device, all internal registers of this sensor appear to be reset to 0x00 (which should not be possible, they should have some defaults values). Thus this makes me suspect that SPI is not actually succeeding in reading those registers, but no error is shown. When, in addition to switching off the device, I also disconnect the UART connector, then the system gets reset properly and registers of the sensor are read correctly.

Can anyone help me understand what is happening?

Thank you in advance. Marco

[Ole Bauck]

The whole chip will stay powered if the voltage on a pin is supplying the chip. When you say that your firmware is not running, may it be because the code has entered an error condition and is stuck in the error handler?

You can of course measure Vdd when the chip is powered off and the UART connector is still connected, to see if what I described in my last comment is the case.