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USB CDC - problems with high datarate

Question asked by Dennis Frie on Aug 9, 2019
Latest reply on Aug 12, 2019 by Dennis Frie

I've been using the USB CDC class from lpcopen for a while, but just been running into a problem when sending too much data from the PC. Basically, the USB CDC is used in a firmware-update chain and all data is forwarded to a traditional RS232 serial output to another device.
The PC-tool (which I can't modify) sends some very large messages (around 10000-20000 bytes), before waiting for a response. Unfortunately, the USB transfer speed is significantly faster than the UART-output, which means all data must be stored in an internal buffer, which is just not practical.

Is it possible to set the USB-state to "busy" or do anything else to indicate, that the USB-device is not ready for more data? The FTDI FT232 seems to solve this problem with a minimal buffer-size, so I guess it's supported in the USB-protocol somehow? 

 

Any help would be much appreciated.

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