pc-ble-driver: Rpc Status Callback reports IO_RESOURCES_UNAVAILABLE with message "The device does not recognize the command."

[pkupper]

Hi all,

I am developing a Windows desktop application using pc-ble-driver 4.1.4 and SoftDevice API v6. The nRF52840 dongle is running the connectivity firmware V4.1.4 with SoftDevice S140 V6.1.1.

When running an automated test script, pc-ble-driver will occasionally send a rpc event with code IO_RESOURCES_UNAVAILABLE and message "serial port write operation on port COM24 failed. Error: The device does not recognize the command. [22]".

Is there a known cause for this issue or a good way to debug this.

[Sigurd]

Hi,

This serial port error may indicate that the USB was detached from the computer, for instance by a device reset. Similar to e.g. this post,  Writing a long characteristic causes NRF_ERROR_SD_RPC_NO_RESPONSE 

If you have any nrf_log output from the connectivity firmware, that might help to e.g. find out what kind of error that might have caused the device to reset. Also, if you are using any USB hubs, I would recommend plugin the device directly to the USB host instead.