user31105: Would it be possible to use TWO MIDI inputs (and a MIDI output) on an Arduino having only one RX/TX serial port? Timing will be somewhat critical so a software serial port is not usable probably. I need to listen continuously to both MIDI (in) ports not to miss messages.
Or is it better to use an Arduino Mega having 4 serial ports?

user4143: Use a Mega. SoftwareSerial is shaky at best and cripples everything else while it runs, and there really is no substitute for real hardware UARTs.
Alternatively look around and see if you can find a board based around the ATMega328-PB (note the "B") which has a second UART built in.

31105: <p>Would it be possible to use TWO MIDI inputs (and a MIDI output) on an Arduino having only one RX/TX serial port? Timing will be somewhat critical so a software serial port is not usable probably. I need to listen continuously to both MIDI (in) ports not to miss messages.</p>

<p>Or is it better to use an Arduino Mega having 4 serial ports?</p>
 4143: <p>Use a Mega. SoftwareSerial is shaky at best and cripples everything else while it runs, and there really is no substitute for real hardware UARTs.</p>

<p>Alternatively look around and see if you can find a board based around the ATMega328-PB (note the "B") which has a second UART built in.</p>
