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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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    As a test I'm just running an UART printing loop. When I power off the chip, messages stop been printed out via UART. When I power up nRF again, it starts again from the bootloader. UART Tx and Rx are connected to pins P0.30 and P0.31, and they feed the nRF with 3.3V. The nRF itself then keeps Vdd to 1.57V. 1.57V is within the absolute maximum voltage supply rating for nRF52 (-0.3V to 3.3V), however it is smaller than the minimum recommended supply voltage (1.7V). This might explain why the firmware stops running. In addition the nRF specification states as well that Pin in/out voltage should fall in the range -0.3V to Vdd+0.3V=1.87V, and this is not the case since nRF gets 3.3V in. I know I am looking at it in the opposite way, since power supply is not coming from Vdd directly, so I am not sure how such specification applies in this case.

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  • 0

    As a test I'm just running an UART printing loop. When I power off the chip, messages stop been printed out via UART. When I power up nRF again, it starts again from the bootloader. UART Tx and Rx are connected to pins P0.30 and P0.31, and they feed the nRF with 3.3V. The nRF itself then keeps Vdd to 1.57V. 1.57V is within the absolute maximum voltage supply rating for nRF52 (-0.3V to 3.3V), however it is smaller than the minimum recommended supply voltage (1.7V). This might explain why the firmware stops running. In addition the nRF specification states as well that Pin in/out voltage should fall in the range -0.3V to Vdd+0.3V=1.87V, and this is not the case since nRF gets 3.3V in. I know I am looking at it in the opposite way, since power supply is not coming from Vdd directly, so I am not sure how such specification applies in this case.

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