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I have a simple sketch working on arduino Uno and Nano sending data using an XBee. However, if I run the project on an Arduino Mega it does not work.

What differences between Uno/Nano and the Mega could be causing issues?

Connection: I just connect 3.3V->3.3V, Gnd->Gnd, and have tried various ports for DIN and DOUT (normally pins 2/4, but have tried A0/A1, 22/23 etc..).

Sketch: pastebin

Have brought a second Mega in case of hardware faults, but the problem persists. Have stripped anything which might be tying up a timer. Am choosing the right board type in the arduino IDE.

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  • Update: changing the sketch to use HardwareSerial works, but I'd like to understand what's different between the devices here. Commented Jan 20, 2019 at 14:43

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Not all arduino Mega pins support 'change interrupts', which is needed for Software Serial. Only the following can be used for RX:

10, 11, 12, 13, 14, 15, 50, 51, 52, 53, A8 (62), A9 (63), A10 (64), A11 (65), A12 (66), A13 (67), A14 (68), A15 (69).

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  • Mega has 4 hardware serial ports, no excuse to be using software serial. Commented Oct 17, 2019 at 16:14

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