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Problem of overwrite buffer sending a large stream of data using  CDC Virtual COM App

Question asked by Francesc Xavier Pastor on Aug 9, 2011
Latest reply on Aug 12, 2011 by Francesc Xavier Pastor



I'm trying to set up an application to send a large stream of data using MCF51MM256. Specifically, I sample a signal which requires to send 500 frames/second by the USB port (each frame weight is about 500 bytes (some of them  more than that because of octet stuffing).


I used the "cdc virtual com project" from "Freescale USB stack with PHDC" as starting point so that I changed several things in usb descriptor & virtual_com files to achieve a full speed USB using Bulk transfer. The problem becomes when I want to send a large stream of data continuosly as I realized the new data overwrites a part of the send data buffer before the system ends the latest sending task. I mean, the time between sending tasks seems not to be as fast as it should be in order to have time to send all the data.


So, I'd like to know if somebody knows what I could change or maybe what I didn't setup properly to achieve my target as I think using a Full Speed 2.0 USB configuration, the speed should be 1.5MB/sec (more than enough for my application) unless the limitation comes from the virtual COM port. In that case, would it be possible to reedit the driver?


thank you very much