dfucons failure if run too soon

[danielpieczko]

Testing manually, I have been replicating the sequence performed by the test_dfu.py testcase: xflash a factory image, get the version number, download an upgrade image, get the new version number, etc.

I have found that if I don't wait before running the command to download an upgrade image, I sometimes get this error:
TUSBAUDIO_StartDfuDownload failed, st=0xEE000047

The command is: dfucons download upgrade1.bin -g{E5A2658B-817D-4A02-A1DE-B628A93DDF5D}

For now, I am just adding a 20s delay into the test as I don't know of a better way to determine if the device is ready for a DFU download, and haven't looked into the dfucons code yet to understand more about this error.

[xross]

We intend to escalate this further to our driver provider, Thesycon.

[xross]

From Thesycon:

The error code 0xEE000047 means TSTATUS_INVALID_INDEX. With status is returned by TUSBAUDIO_StartDfuDownload when the previous call to TUSBAUDIO_EnumerateDevices result in an empty list. That means currently no device is found.
You can retry to call TUSBAUDIO_EnumerateDevices and check with TUSBAUDIO_GetDeviceCount if a device is connected.
After a fresh reconnect it could be that it takes some time until the driver is installed and loaded.
The dfucons does no retry internally with a timeout it just exit if no device is found.