Problem with USB UART when exactly 64 Byte string is transmitted



Question: When a packet of exactly 64 Bytes is transmitted using USBUART from PSoC to a PC and the result observed on a Terminal program, nothing is displayed on the Terminal program on the PC.

Response: This is because of a bug in the USBUART User module code.  The firmware is supposed to send a zero length packet after sending the 64 byte packet.  The driver in the PC will know of the reception of the string only after receiving this zero length packet.  As the firmware does not send the zero length packet, the PC driver is not aware of the reception of the data.  This problem occurs only for a packet of exactly 64 characters.  Packets with other lengths are received fine.  The workaround for this problem is to split the 64 byte packet into two packets of any lengths, for example 32 + 32, or 62 + 2 etc.

This problem will be fixed in PSD5.0 SP6, which is expected by the end of September 2009.