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
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.