I can confirm it is broken in 7.1 and 7.2 firmware. It fails our serial loopback factory test and does not work with SC.

I can get it to work when I enable (#if 0 -> #if 1) the uart state machine shortcut in vfd_set_uart_pin_mask(). The currently checked in file only enables the knob.

The other change needed to make it work again (which I do not yet understand why it is needed) is to set UART_VP_TX_FIFO_SIZE back to 64 (was 64 in 7.0, but is currently 32).

I did not check-in my changes as I'd like Sean to comment on it first in case he thinks it might break something he implemented to make the knob work better.

Created attachment 3785 [details]
Possible RS232 fix

Sean: Could you please check the attached proposal to fix RS232? If you think it is ok, I'm going ahead and check it in. Thanks.

The fix basically enables your UART shortcut function to check the external RS232 and not only the knob. Also the transmit buffer needs to be 64 bytes instead of 32. (I was unable to figure out why that is though.)

Applying the fix still leaves the knob working properly, I think. However I wouldn't know what to look for in that regard. Would the knob stop working at all if the fix was bad?

It looks OK to me. 

Fixed in rev 4719, will be in TR fw 60.

Verified in SC 7.2 - 22900

This bug has been fixed in the 7.3.0 release version of SqueezeCenter!

Please download the new version from http://www.slimdevices.com/su_downloads.html if you haven't already.  

If you are still experiencing this problem, feel free to reopen the bug with your new comments and we'll have another look.