2xCDC + 1xMSC in USB high speed mode on a SAME70

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#1
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Dear all,

 

I tried to setup 2xCDC + 1xMSC in USB high speed mode on a SAME70 device using ASF3 (ATMEL STUDIO plugin). So far I didn't get it to work. Full Speed works as expected. I guess it is related to the number of endpoints that are available. Both CDC consumes already 3. I think I read something that in USB high speed mode the MSC consumes altogether 4. The SAME70 has 10 endpoints available. However, I think EP0 is reserved for control. So I'm missing 1 EP - is this correct or is there a way to set up everything as I like to do (see subject)?

 

Best Regards

Markus

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Total votes: 0

I will discuss a little bit further with myself :-)

In the meantime I have doubts if it will work in high speed because the USB internal DPRAM has 4096bytes. For each CDC interface you need three endpoints. For the MSC you need 2 endpoints. Together that is 8 endpoints. According to USB specification each of them needs 512bytes. That is 4096bytes. However PEP_0 will add another 64 bytes that is not available anymore. 
Therefore it will be impossible to have 2 CDC and 1 MSC in high speed mode. Is this correct? Or is there any workaround to overcome this problem? The only possible solution I can think of is making use of the bidirectional feature of the endpoints. I will work towards this direction and see if it helps.

 

Best Regards
Markus