Trouble Shooting

Symptom Things to try
Can't get into programming mode Try the hardware buttons...
  • Press and hold the HWB button
  • Press and release the RST button
  • Release the HWB button

This should always get into the bootloader firmware.  The bootloader can't be erased unless a hardware programmer erases it.

Windows XP can get upset with the device jumping from mode to mode.  It may just be that device isn't being recognised.  Try unplugging it and then plugging it in again.  Try a reboot if that doesn't work.

Windows XP keeps blue screening I've seen this a couple of times when two identical devices are plugged in.  I even found a knowledge base article about it, saying it will happen if 2 identical devices are connected, but since then I haven't been able to reproduce the problem.  Maybe it was a Windows Update.  Let me know if it happens to you.  The work around is to give the devices different serial numbers.
Device doesn't appear in Linux, or Windows reports "Unrecognised device". If this occurs after programming the device, there may be bugs in the firmware.  Contact the developer at

If this happens and you can't get back into boot loader mode, follow the following instructions...

  • Disconnect the device.
  • With one hand, press and hold the RST button.
  • With the other hand, press and hold the HWB button.
  • With another hand, connect the device to a different USB port than was used previously.
  • Release the RST button.
  • Release the HWB button.

When an invalid USB device is connected to windows, the operating system can get upset and will not allow you to reuse the port.  Using the standard HWB/RST method won't work because windows still thinks the unrecognised device is plugged in.

After the device is programmed, it doesn't appear in linux or windows. If the power requirements for the device are too high for the USB Port/HUB, the device will just be ignored without any error messages.  For a device that uses a lot of power, make sure you use a powered USB hub, and the power is connected.
Generic HID can't find the device in programming or regular mode. The libusb drivers can be finicky.  Try rebooting.  Try reinstalling the libusb-win32 filter driver.
Other USB devices fail under Windows. The libusb-win32 filter driver can effect other devices.  After you have finished building your GenericHID device, unistall the libusb-win32 filter drivers.
In the programming dialog, GenericHID complains with the message "More than one GenericHID device (GenericHID or AT90USB128 in DFU mode) found in the system. This may be a USB driver glitch; in this case you can ignore the message. If there are multiple devices plugged in, you may program the wrong one." To be able to program the device correctly, only one GenericHID device must be present.  This message will be displayed when more than one GenericHID devices, or AT90USB1287 devices in programming mode are detected.

Note that this message can be incorrectly displayed because of driver conflicts between libusb and other device drivers.  It is left to the user to ensure the correct device is plugged in.

Can't locate the device under linux. By default Linux will not allow access to the device unless it is explicitly configured, or the application is running as the root user.