Memos From the Cube

Good news! About a week ago, I managed to get an initial implementation of Microsoft’s RNDIS specification working as a MyUSB demo, so that the USB AVRs could be enumerated as a network adapter on modern OSes (yes, Linux has RNDIS support now).

That implementation made it into the 1.5.1 MyUSB release two days ago. However, the demo was limited; it could only send/receive raw Ethernet frames, it didn’t perform any processing on them as that was left up to the application engineer. It also failed to work on older Linux kernels with the original RNDIS implementation, due to a flaw in the Linux code — the notification endpoint was ignored in favour of polling the control endpoint, causing a lockup while the device waited for the notification endpoint to become empty again.

Both of those issues have now been resolved in the latest working code, with a big thanks to AVRFreaks member Colin O’Flynn for his advice and debugging help. The demo now works on the older RNDIS Linux code, and it can do something with the Ethernet frames!
Currently, I’ve written up protocol handlers for Ethernet, ARP, IP and ICMP, with TCP a work in progress. That’s the bare minimum to get a pingable device:

Which is damn cool in my opinion — if only because I’ve spent a whole week getting this far. Once I get TCP working, I’ll be able to write up a simple webserver, with the ultimate goal of being able to control the board LEDs using a web browser.

What’s the utility of all this? Think how much easier a device would be to configure if you could just plug it into a laptop, navigate to it with a web browser (on any platform) and change configuration settings using native widgets. No more complex serial terminals!

Stay tuned for updates.

Additional: For those with good eyesight and inquisitive minds – the 300ms+ ping time is due to the USBKEY printing out the protocol details of each packet through the serial port for debugging.