dundakitty

CTS is an input, RTS is an output. The output of an 74HC14 inverter connects to the CTS-XBAR pin. The RTS signal from the other teensy connects to the input of the 74HC14 inverter. The diagram here: uart flow control may help. You can ignore...

You will indeed need to invert the CTS output. If you switch to Serial3 instead of Serial1 you can use pin 19 for CTS and not need an inverting buffer. If you can't use Serial3 and have two unused pins on your teensy you can build your own...

I've used a 12-position rotary switch as an input. I put 1K resistors between each terminal, creating a voltage divider. The last terminal goes to ground, the first terminal through another 1K resistor to +3.3v. The wiper goes to an analog...