Software Design Considerations

Abstract  Design and build a compact robot to traverse a maze  Use the robot to generate an ASCII representation of the entire maze  Mark light locations on map as they are discovered  Revisit lights intelligently throughout the maze in a user-defined order

Software Design Considerations  PIC18F4550 Microcontroller Interfaces General Purpose I/O A/D sensors PWM motor control Communication with compass via I2C Data transfer via USB  “Flag”-driven Design  Embedded C

General Purpose I/O  5 registers for general purpose I/O  PORTx registers refer to pin  TRISx registers: 0 – output 1 – input  3X Single-colored LEDs  1X RGB LED (3 pins)  2X Pushbuttons  4X Motor direction control

A/D Sensors  13 A/D Channels  Conversion process Set channel to corresponding ANx pin Set GO_DONE bit to 1 Conversion complete when GO_DONE bit = 0  1X RGB Color Sensor (3 pins)  3X Short-range sensor  1X Long-range sensor

PWM  PWM enable by setting bits 2 and 3 of the CCPxCON register CCP1 CCP2  Motor speed control  Alter duty cycle to change speed

I2C / USB  Communication between compass and microcontroller via I2C  Data transfer to computer with USB Byte-by-byte transfer of data Data structure decoded by PC

Flowchart for Main Loop

Power On / User Input

Maze Mapping

typedef struct _mazeNode { /* bits 7-5: 000 = normal node 001 = red 010 = green 011 = blue bits 4-0: location from -10 to 10 */ char locX; // holds X location char locY; // holds Y location // holds the path description /* bits 7 & 6: 00 = nothing 01 = entrance 10 = return 11 = unused bits 5-0: index of the next node in mazeNode array */ char Npath; char Spath; char Epath; char Wpath; } mazeNode;

Tremaux’s Algorithm

[1] Tremaux’s Algorithm

Revisit Lights / USB Transfer

Hierarchical Block Diagram of Code Organization

References  [1] David B Suits, “Playing With Mazes,” Rochester, NY, 1994