Make DMX Rx work on Teensy 3.2, only tested on Serial1 so far
Make DMX Rx work on Teensy 3.2, only tested on Serial1 so far

(cherry picked from commit 3cb4fea299b99b1a60624ebc12418bfd24dda694)

chrisstaite/TeensyDmx,chrisstaite/TeensyDmx,chrisstaite/TeensyDmx