I did try your suggestion without any luck.
Did you also change the RX handler to receive only 1 byte at a time? Waiting for a whole string takes a LONG time.

And, have you tried the XIN without the interrupts? Is XIN working at all?
You can add a Timeout to XIN, in case it's not receiving anything.

Is the XIN supposed to be running continuously in a loop, or as a response to the 250 command?
If it was in response to the command, it's more likely that incoming data will not occur again in the middle of the XIN.
<br>