USB CDC VCOM User defined device example consecutive RX fail

[akspurr]

Hello,

Recently I worked through your very useful user defined device class application note, based on the cdc_vcom example: https://www.nxp.com/docs/en/application-note/AN14169.pdf

The code is functioning as I would expect, except for when I modify the AppTask to receive multiple packets prior to sending a response back to the host.

It seems that the USB stack forces a Send for every Recv, something which other users have noted (e.g https://community.nxp.com/t5/i-MX-RT-Crossover-MCUs/ESC-character-in-virtual-com-port-example/m-p/11...).

Is there a way to modify the stack to allow for multiple consecutive Recv?

Thanks,

Alex 

[EdwinHz · Accepted solution]

Hi @akspurr,

Unfortunately, the stack is designed to do a send after every receive by design, so no modifications should be made to the USB stack to prevent this behavior.

BR,
Edwin.

[akspurr]

Hi @EdwinHz,

Ah, I see, in that case I'll keep a workaround in place.

Thanks for the fast reply, you've saved me a lot of debugging time!.

Cheers,

Alex