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USB, DMA, CDC and Speed ... Is it possible?

Question asked by devine.gareth on Jun 25, 2012
Latest reply on Jun 27, 2012 by Chinzei.Tsuneo
Hi all,

I have a fair bit of experience with the STM32 now and have got most peripherals working as I want on multiple projects but I am yet to master the USB.

I would like to transfer data collected by a series of sensors over USB to a host PC.
The key details are:-

Data load is not flat but event driven
Peak data load is around 160Mbit/s
Average data load is 60Mbit/s

So far I have managed 20Mbits/s using a modified version of the CDC example for the STM32F2x7 series (increased buffer sizes, changed output fifo to handled wrap around etc).

However 20Mbit/s seems to be my limit. Looking at the packets it looks as if the device is wasting time starting and ending transactions rather than sending continous packets
during peak flow. I am not too sure why this is as data is alwasy in the output buffer.

 Does anyone have any experience with such a project or recomendations of how I should proceed? Has anyone ported the example to work with the DMA and got better results? 

 Discussions welcome, I would just like to learn more on this.

Many Thanks,

Gareth

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