Specifications

System Model

The following data flow diagram shows the basic flow of values through the system.

Process 1:

This is the main section of the program. It runs a tight loop checking for data from the

sensors on port A and also checking the odometer readings to initiate a compare

function to maintain straight line driving.

Process 2:

Process 2 is a large subroutine called every time a turn is needed. It accesses data from

port A. It checks sensors and turns relative to the status of them. After the motors have

been adjusted to gain desired performance the code returns to the main loop, process 1.

Process 3:

This is an interrupt service routine that determines which odometer sensor has triggered

and increments the respective counter. The counter is a byte stored in memory and is

cleared regularly to avoid overflow issues.

Process 4:

This process is a subroutine used to maintain straight line driving. It is called from the

main program loop and works by comparing the odometer counters and adjusting motor

speeds to maintain a constant even speed between the motors. This results in even

wheel speed hence straight driving.

PORT

Obstacle

Odometer

readings

Process 1

MOTOR

CONTROL

Process 3

Process 4

D1 = Signal of which direction to turn

D2 = odometer counters

D3 = motor information for turning

D4 = motor information for drive straight

D5 = jump to process 4 when required

PORT

sensors

Process 2