I was just wondering if something changed recently regarding pins #18 and #19 on the Arduino as far as not being able to use it for input multiplexers. I've had one on pin #18 with 14 of the pins used and it was working perfectly for many months then suddenly it stopped working like a month ago. Not sure it it was somewhere around version 0.9.46.

   So I moved it from pin #18 to #19 and it still didn't work. I checked all my wiring and even replaced it a new MUX board but it still didn't work on those pins. After wondering what it could be I decided to change it to pin #34 and everything worked again. I also tried it on pin #42 and it also works perfectly on that one.  So I just wondered if pins #14 through #19 connot be used for MUX boards.
Nov 23, 2019 in Input Controls by

1 Answer


All colored pins (14-19) are reserved for 3 Serial ports, to connect slave boards, servo, steppers, key-matrix and LCD (later the list of slave boards will be expanded). As you can see the color is matched with the slave device buttons above the main table.

If you don't have any assigned   steppers or matrix board the pins 18,19 (Serial #3) can be used as usual. If not, we will check this later.

Nov 23, 2019 by