NXPUSBlib CDC miss DMA EndTransfer interrupt for messages of 64 bytes

Discussion created by lpcware Employee on Jun 15, 2016
Content originally posted in LPCWare by Andrea Colombo on Fri May 03 05:48:12 MST 2013

I'm performing some test with NXPUSBlib (CDC class) on LPC1758 and I have this strange behavior: After the connection with the PC, that loads correctly the new COM port, I send packages of different size to the device. It seems to work everything well because for each message I have an interrupt for DMA NewTransferRequest at the beginning of the transmission and an interrupt for DMA EndTransfer at the end of the transmission. Unfortunately if my package is of 64 bytes size I see only the interrupt for DMA NewTransferRequest, but the interrupt for DMA EndTransfer doesn't happen. The packet isn't lost because, if I send a new message of a different dimension I can see all the interrupts and I can find in the buffer both the sent messages.
Do you have some suggestion to debug or fix this problem?