USB problem when packet length is multiple of TX buffer size

[daveh]

Hello, I'm using a PIC1865J50 to transmit packets via USB to a computer. On the computer side I'm using a C++ program using Microchip's mpusbapi. My program is a variation of Microchip's "Example 02 - Run-Time Linking".

My problem is this, when the computer receives a packet that is a multiple of the tx buffer size the program is ok the first time around, but subsequent attempts to receive cause an error. My TX buffer is 64bytes, so a receive size of 511 works fine as does 513, but 512 fails.

I got the latest USB driver files from CCS and in USB.c it appears they correctly send a 0-length packet if the previous one was full. I'm guessing Microchip's MPUSBRead() function isn't properly handling this.

Anyone see this problem before?