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nRF52832 IO problem

Hello!

We have nRF52832 chip on our product and we have some problem with one of its IOs.. We configured P0.16 as RX of UART, And when we run it we see this behavior of this IO:

VCC (yellow) vs P0.16 (green) that configured as UART_RX

Here we see that with rising of VCC (yellow signal) IO (green) rising to almost 1V when it supposed to still at 0V. Important note: we disable and enable VCC fast here so we see that before rising of VCC it don't have 0V. This behaviour is very problematic to our system. Because we have power supply sensitive sensor that connected to this UART. This spike of voltage damage sensor that connected to this IO.

We tried to load to evaluation board same version of SW on nRF52832 and we got next result:

We see that also here we have the problematic spike.

When we erased the evaluation board - we got the same result.

Is this IO known as problematic?

Thank you

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  • It seems very curious that the sensor is getting damaged due to a spike that's <1V for just a small period of time.  

    For a typical UART configuration, the 'inactive' state will be HI and a transmission starts with the transition from HI-LOW, indicating the start bit when a byte is arriving.  Even after the little 'bump' on power-up (which seems very reasonable, it takes a small amount of time for the processor to get control of the IO), I would expect that the UART RX line would get pulled hi, especially with the 100k pull-up that you mention.  Something is strange here.    

    You also mention that your sensor is powered off of 9V.  I assume you're using some sort of level-shifter to make sure that any signals sent to the NRF are down at a safe voltage level, correct?

    Cheers,

    Roger

  • Yeah, it is also very strange for us also..

    The sensor powered by 9V, but it have on-sensor buck converter that convert 9V to 3.3V to power-up the on-sensor microprocessor MSP430G2744. This on-sensor microprocessor is the part that communicate via UART with nRF. The 9V used only for accelerometer that placed on the sensor.

    As I write this I am thinking about something - is this possible that on-sensor buck output come lately after the signals from nRF?.. Need to check this.

  • There will be some small start-up time for the buck but it is probably very minimal.  It sounds like your timing is very critical between the NRF and your sensor.  Perhaps it makes sense to wait for a delay (a few mS) after startup, then have your NRF pull the reset line of the MSP430, and then start your communication.  This way you can guarantee that everything is fully powered up before you try to pass data between the micros.

    Even with that said, I still do not understand why your UART RX line is low even when there is a 100k pull-up.  If that condition is still there even after everything has been powered up and configured, there is a hardware problem or a configuration problem somewhere and that issue needs to be resolved before going any further.

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  • There will be some small start-up time for the buck but it is probably very minimal.  It sounds like your timing is very critical between the NRF and your sensor.  Perhaps it makes sense to wait for a delay (a few mS) after startup, then have your NRF pull the reset line of the MSP430, and then start your communication.  This way you can guarantee that everything is fully powered up before you try to pass data between the micros.

    Even with that said, I still do not understand why your UART RX line is low even when there is a 100k pull-up.  If that condition is still there even after everything has been powered up and configured, there is a hardware problem or a configuration problem somewhere and that issue needs to be resolved before going any further.

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