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Full duplex mode with USB CDC-ACM

Question asked by Bryce Lembke on Jun 13, 2016
Latest reply on Jun 17, 2016 by Bryce Lembke

I have a TWR-K65F180M as a full speed cdc host (using USB0 - KHCI) and a custom board (using USB1 - EHCI) as a high speed CDC device. My custom board enumerates fine with Windows and sends serial traffic just fine as well (high speed mode). When I plug it into my TWR-K65F180M, I can see on my analyzer that it negotiates to full speed and enumerates correctly (all the control descriptors seem to be exchanged just fine), but none of my IN packets are getting sent to the host, though I do see the periodic SOF packets.


Comparing the trace of descriptors, the only differences are related to full speed vs high speed (frame sizes, etc).


I am using the SDK_2.0 usb_cdc_host example code (with KHCI). If I switch to use the usb_host_hid_mouse example and plug in a mouse, it works great, so I think that electrically, everything is good.


Aside from setting the KHCI flag on the host (and EHCI flag on the device), is there something else I need for this to work?