We are designing a system with the cypress USB chip in slave FIFO mode talking to a FPGA. the firmware is based on the AN61345 application note.
Its configured in in slave FIFO mode with EP2,4,6,8 using double buffering. In 8% of the cases, when the user application tries to send data packets, the cypress issues a NYET response. then the PING-NAK times out. Then the PC stops sending any more requests to the chip over the wire. We observed it with a USB protocol analyzer. When the cypress firmware enters this state it does not recover till we unplug it and plug it back in. Then communication resumes. We are completely lost on what would cause this. EP2 is OUT, EP4 is IN, EP6 is OUT, EP8 is IN. Its a self powered device but in firmware its configured as a bus powered device. I don't know what the impact of this is. Also, I had to disable the system going into "Sleep" mode to see if it worked. But it did not when the PC was powered on first and then the instrument was turned on.
We are completely confused what could be causing this error, and It needs to be fixed soon. Please help.
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