Serial communication was used
to transmit the value of the tilt sensor from the PIC microcontroller
to the host computer (com port 1) and again to return the resultant
motor duty cycle computed by the host computer to the PIC microcontroller.
The default transmission rate
for the com port used was 9600 baud, or 9600 bits per second.
Testing at this data rate proved to be sufficient and so it was
maintained through the course of this project.
As the PIC microcontroller uses
only TTL levels and the serial port of the host computer uses
RS232 levels, a converter would be required. Recalling from a
previous data communications lab at BCIT where the ICs MC1488
and MC1489 were used for this purpose, they were then selected
to be implemented in this project as well. The MC1488 line driver
converts TTL levels into corresponding RS232 levels, while the
MC1489 receiver does the opposite.