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USB CDC HUB read is blocking in highspeed

Question asked by JINS PAUL on Sep 26, 2017

Hello All,

Good day.

The USB CDC read call implementation in usb_host_cdc.c (mqx stack version 4.1) ,i.e, _lwevent_wait_ticks(event,USB_DATA_READ_COMPLETE | USB_DATA_DETACH, FALSE, 0) “waits” on “event” object forever until it receives data on USB port. The USB ISR should trigger “release” of the “event” when data is available but when CDC Wi-fi dongle connected to a high speed port(through USB hub IC  2512) to K70 board, it is observed that the event USB_DATA_READ_COMPLETE does not occur even after an extended period of time(over 5 minutes).

Possible reasons:

  • ISR overloading?
  • Data isn’t being read / minimum data needed for high speed operation is not present on the bus?



However if the same CDC Wi-fi dongle is connected to the USB full speed port, the communication proceeds perfectly. Kindly help to identify the root cause and resolve the issue.


Thanks in advance,