This is not a question. I think it's a bug (or maybe because my china arduino MEGA and UNO) and should be described at I have been weeks to discovered it.

Firstly I have at MEGA Tx19 and Rx18. And UNO RX0 and TX1. !Upsidedown Matrixkey web¡

MatrixKey wiring page says I have to join MEGA Tx with UNO Rx but this is not ok for me.
It only works joining Tx19 with Tx1 and Rx18 with Rx.
1 month ago in Wiring, Powering by

1 Answer

It's because you have those mega board that have wrong labels for Serial #1 (but correct functionality, as serial #0, #2 and #3 which all are correct labeled).

You should connect exactly as it's described on the page: pin#18 from master to the slave Rx and pin #19 to the slave Tx.


1 month ago by
Thanks Vlad. I think the same.

Worst of all, I have two MEGAs from apparently different china producer, but pin 18 are both RX instead an original MEGA Tx.
It's absolutely not critical.
I also have one of this board (it used in my test platform), and it is totally fine.

It's nothing wrong with pin 18  - it is Tx1 as it should be of course, just lettering as Rx1.

And it's easy to figure out, looking on other serial ports.