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1. 

   GuzZzt
   Member

   I have a problem with the serial output in Linux (Ubuntu 10.4.1 LTS). I can most of the times not auto reset the board so I must press the RST button, but that is not the main problem. When I connect the board /dev/ttyACM0 is in the list but if I turn on the serial monitor that port is almost immediately removed and I instead get /dev/ttyACM1. If I change to that port and start the serial monitor again it changes back... I most of the times get only a few lines of output or none at all. This is very frustrating.

   The program is very simple, a loop that every 100 ms outputs a value from a gyro read by analogRead().

   (I'm new to Linux so I don't know how to debug this. I switched to Linux because I found it working even worse in Windows Vista x64.)

   Posted 5 years ago #
2. 

   GuzZzt
   Member

   Never mind, I found it myself. It was a hardware problem, I used too much power and that seems to be the cause of the instability. It works fine with an external power source.

   Posted 5 years ago #
3. 

   poslathian
   LeafLabs

   Very interesting. I was going to suggest it was a timing thing.
   In linux, if you try an open a nonexistant serial port on /dev/ttyACM0, then if a serial device does suddenly crop up, it gets bounced to /dev/ttyACM1,2,3...etc

   This is exactly what happens if you reset the board and then immediately try and open the serial port. the USB init function gets called as part of the user code, not the bootloader. So directly after reset, there is no serial port for about 4 seconds.

   Autoreset seems finicky for unknown reasons, especially when using additional peripherals like lots of timers or interrupts. We are working on this issue.

   Posted 5 years ago #

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