example throws error

the first exchange "who_are_you" works fine, however for the sequence

c.send("sum_two_ints",4,1)
msg = c.receive()

python 3.6 throws this error on the receive line:
struct.error: unpack requires a buffer of 2 bytes

[headrotor]

This is probably caused by using a different microcontroller than the default Atmel. This worked for me on a Teensy (arm)

       # Board input parameters:
       #      int_bytes: number of bytes to store an integer
       #      long_bytes: number of bytes to store a long
       #      float_bytes: number of bytes to store a float
       #      double_bytes: number of bytes to store a double``

       #  These can be looked up here:
       #      https://www.arduino.cc/en/Reference/HomePage (under data types)`


arduino = PyCmdMessenger.ArduinoBoard("/dev/ttyACM0",baud_rate=9600)
teensy = PyCmdMessenger.ArduinoBoard("/dev/ttyACM0",
                                     int_bytes=4,
                                     baud_rate=9600)

...
# Initialize the messenger
c = PyCmdMessenger.CmdMessenger(teensy,commands)