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Arduino - SoftwareSerial library and interrupts

I wanted to use sleep functions of the ATMega (in power down mode), and the Arduino's software serial library: it turns out that all interrupt vectors are enabled in sleep mode.

So the workaround is to start the serial communication when needed with softSerial.begin( BAUD_RATE)), then stop it with softSerial.end().
Also, the .end() can be just before going to sleep, and the .begin() just after.