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9.2. Reviving using AVRDUDE

This section explains a special method for reviving an A-Star (or another of our 32U4 family of boards) using the command-line utility AVRDUDE in case your usual method of programming is not working. AVRDUDE stands for “AVR Downloader/UploaDEr”, and it is compatible with the A-Star bootloader.

If you have an A-Star 32U4 Micro, you should connect a momentary pushbutton between the GND and RST pins to serve as a reset button. Other boards in our 32U4 family have a reset button you can use. Alternatively, you can use a wire to temporarily connect GND and RST together instead of using a reset button.

  1. Connect the device to your computer via USB.
  2. Prepare the computer to show you a list of its virtual serial ports. If you are using Windows, this means you should open the Device Manager. If you are on Linux or Mac OS X, this means you should open a Terminal and type the command ls /dev/tty* but do not press enter until the board is in bootloader mode in the next step.
  3. Press the reset button twice within 750 ms to make the AVR go into bootloader mode. You should see the yellow LED fading in and out when the AVR is in bootloader mode. While it is in bootloader mode, quickly look at the list of serial ports provided by your operating system in order to determine what port the bootloader is assigned to.
  4. Type the following command in your terminal and replace COM4 with the name of the bootloader’s serial port, but do not press enter yet. This command will erase the malfunctioning program on the device but preserve the bootloader.
    avrdude -c avr109 -p atmega32U4 -P COM4 -e
  5. Press the reset button twice within 750 ms to make the AVR go into bootloader mode.
  6. Quickly run the command you typed previously. The command needs to be run within 8 seconds of starting the bootloader, or else the bootloader will exit and try to run the malfunctioning program again.

By following the instructions above, the malfunctioning program on the device will be erased and the device will stay in bootloader mode indefinitely. You can now load another program onto it using the Arduino IDE or AVRDUDE.

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