OpenOCD Troubleshooting: Device Not Opened (Linux)

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On startup you see an error message indicating that OpenOCD cannot find the device. If your build of OpenOCD uses the libftdi driver library, the error message reads:

Error: unable to open ftdi device: device not opened
Device Not Opened error with libftd2xx

With OpenOCD 0.4.0 this error appears as:

Error: unable to open ftdi device: 3

Try the following to correct the issue.

Manually Unload the FTDI_SIO Driver

OpenOCD should unload the ftdi_sio kernel module automatically on startup. If it fails, you will see the "device not opened" error. You can correct this by manually unloading the module with this command:

sudo rmmod ftdi_sio

You should see no text output, and the command prompt should appear again immediately. You should now be able to start OpenOCD successfully.