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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

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  • 0

    Thank you Ole for your support. Your help together with this link are the answer: devzone.nordicsemi.com/.../ It turned out that my sensor was not resetting according to its specifications. This was happening because the sensor did not get powered off properly (1.57V in due to UART pins). Is there any way I could force the UART pins to "disconnect" so that any voltage on UART won't affect the system?

  • 0 in reply to Marco

    Yes, in my previous message I was stressing on the pins (rather than on the UART). As you said the problem is not the UART itself, but the rx/tx pins connected to the nRF and providing 3.3V even when the nRF is unpowered. I was wondering if there is any way (e.g. a nRF internal switch) that would allow me to force the nRF to keep the 2 GPIO pins (connected to the external UART RX and TX lines) "disconnected"/floating from the nRF internal circuitry. Thank you.

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  • 0 in reply to Marco

    Yes, in my previous message I was stressing on the pins (rather than on the UART). As you said the problem is not the UART itself, but the rx/tx pins connected to the nRF and providing 3.3V even when the nRF is unpowered. I was wondering if there is any way (e.g. a nRF internal switch) that would allow me to force the nRF to keep the 2 GPIO pins (connected to the external UART RX and TX lines) "disconnected"/floating from the nRF internal circuitry. Thank you.

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