I have a setup where my Pi Zero W (Pi0W) is connected to an Arduino Due via OTG cable adaptor. My Pi0W seems to reset the Due again when it's about to finish starting up (around 30-40sec mark).

The issue that I'm facing is rather peculiar:

  1. When I power up Pi0W connected to Due it resets the Due.
  2. When I power up Pi0W and Due separately, it does not reset the Due.

This led to me believe that some service during startup is resetting the Arduino Due. Is there a method to identify which service is causing the reset?

Additional info

  1. I initially thought it was my script, but after removing my script completely the same behaviour persists.
  2. I have programmed the 16U2 on the Due and suppressed the reset following this blog. I have verified that it does not reset when connecting to the Pi after it has finished startup. Also tried with my laptop via PuTTY (Flow control DSR/DTR).
  3. I am using Linux raspberrypi 4.19.97+ #1294 Thu Jan 30 13:10:54 GMT 2020 armv6l GNU/Linux, haven't made any modification on USB either.
  4. Both devices are separately powered.
  • Nothing to do with the Pi. Most Arduino reset when connected.
    – Milliways
    Nov 16, 2020 at 1:47
  • Thanks, but that's not the case with Due. I was able to disable auto-reset when connecting to my laptop and accessing via PuTTY. Also successful when connecting to the Pi. It seems that reset only happens during the Pi0W startup process.
    – bot1131357
    Nov 16, 2020 at 2:09
  • How have you configured the USB port? I've seen junk on the UART during start-up that looks like there is a random 'cr' being sent by the kernel (guess a debug left in) but not seen resets on USB devices (i.e. with nothing in config.txt) - how are you powering the Due - from the OTG / GPIO or separate power lines? Running the OTG as networking does not drop the link either.
    – user115418
    Nov 16, 2020 at 2:17
  • There hasn't been any configuration. I'm running raspberrypi 4.19.97+ #1294 Thu Jan 30 13:10:54 GMT 2020 armv6l, as is. Due and Pi are separately powered. Also, <CR> shouldn't cause resets. I suspected some software flow control character, but at this point I'm not sure how to verify...
    – bot1131357
    Nov 16, 2020 at 2:28
  • The <cr> was UART not USB. What type of device does the Due show up as when you run sudo lsusb - The laptop note is a bit baffling as DSR/DTr is serial not USB???
    – user115418
    Nov 16, 2020 at 4:10


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