The I/O for the controls of the pinball machine is done using an OnTrak ADR2200 data acquisition device via the serial port.

ADR2200 writes it's command to the SerialIO object, which uses a SerialPort object to communicate on the serial port.

• SerialIO writes and reads to and from queues in the SerialPort.
• SerialPort controls the serial port. It polls the serial port for data to read in via SerialIO.
• When data is available to be written, data is written to the serial port via SerialIO.