Builders guide robot pacman.pdf

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6.0 Microcontroller and SoftwareOur microcontroller of choice was the Microchip PIC16F877. MicroCore-11microcontrollers using the Motorola HC11 are provided by the lab but upon furtherconsideration, they were rejected for a number of reasons. The project consists of tworobots, each of which requires a microcontroller. One MicroCore-11 costs around $100and using two would already consume half of our budget constraint of $400.Financial issues aside, its functionality were also inadequate for our purposes.Interfacing with RF requires at least 3 pins to decode the four direction signals: up, down,left, and right, and also to indicate the presence of an RF signal. Two stepper motors areused on each robot and each stepper motor driver chip requires 2 pins for stepping anddirection, for a total of 4 pins. An LCD display uses 3 pins for counting lives, score, andreset. Ghost contact and maze-dot counting require 1 pin each for a total of 2. Obstaclesensors use LEDs and this requires a minimum of 1 pin to power if we power them alltogether. This already totals to a requirement of 13 pins, which exceeds the 12 digitalpins available on the MicroCore-11.While searching for a microcontroller with a high pin count and minimal cost, we cameacross the Microchip PICmicro MCU series, with up to 32 I/O pins in the 40-pin packageand a retail price of around $10, one-tenth of the price of a MicroCore-11. Of thePICmicro series, we picked the PIC16F877 based on its popularity (a large amount ofinformation and support from hobbyists were found on the Internet) and because it hadthe largest flash memory size of its class.Drawbacks of the PIC16F877 are that its memory size is slightly small at 8K x 14 words,(although it is expandable externally) and because it is not packaged in a module like theMicroCore-11. Some of the external circuitry required on the PIC16F877 was a clockoscillator, which we chose to be at 4 MHz and a programmer to write to the flashmemory. The advantages, however, outweigh the drawbacks for our purposes eventhough we may start off more slowly because the programming could not begin until webuilt the programmer.There are essentially two software designs in the Pac-Man project—one for the Pac-Manrobot and one for the Ghost. Though they are very different in functionality and as aresult, in implementation, they both play the central role in system integration. Eachrobot also interfaces to different hardware modules and so these modules are discussed asseparate software functions below.6.1 Pac-Man RobotThe goal of the Pac-Man robot is to receive from the user wireless control signalsto move it around the maze. Obstacle sensors guide its navigation. As it traversesthrough the maze, it collects and counts the dots on the floor and displays it on an23
LCD. If it comes in contact with the Ghost robot, it will freeze in shock for a fewseconds before recovering.Six modules are identified in the Pac-Man robot that help it achieve its abovegoal.• Obstacle sensors (front, left, right) prevent Pac-Man from running intomaze walls and help straighten itself if it is off-centred.• An LCD display shows the number of dots Pac-Man has collected and thenumber of times it has been caught by the Ghost.• RF controls the direction of movement of Pac-Man around the maze.• Stepper motors perform the actual movement of the robot.• The maze-dot sensor looks for the LEDs on the floor that it will “collect.”• The Ghost contact sensor notifies the event of being caught by the Ghost.LCD displayObstacle Sensors(front, left, right)RF ReceiverStepper MotorsPIC16F877MicrocontrollerMaze Dot SensorGhost ContactSensorFigure 30. Architectural model of Pac-Man softwareGiven these modules, the pin assignments they require are laid out as follows.Note that the RF signal, Ghost contact, and maze-dot sensor are events that canhappen at any point during the game so the pin assignments are chosen on pins38-40 such that they are handled by an interrupt service routine. Also, pins 2-9are analog inputs so that right, left, and front obstacle sensors can estimate thedistance from a wall as a function of the voltage input.24
Page 1 and 2: PAC-MANEECE 474 - Team 1July 24, 20
Page 3 and 4: Table of ContentsList of Tables ...
Page 5 and 6: List of TablesTable 1. Encoding sch
Page 7 and 8: AbstractThe EECE474 Pac-Man project
Page 9 and 10: 2.0 ChassisThe design objective of
Page 11: casters in the back. For any two wh
Page 14 and 15: Figure 10. 55M048B2U 12VDC Unipolar
Page 16 and 17: 4.0 Radio Frequency ApplicationSinc
Page 18 and 19: Table 1. Encoding schemeUp 100Left
Page 20 and 21: is held for several clock cycles an
Page 22 and 23: Figure 20. Receiver Block DiagramTh
Page 24 and 25: Figure 21. GP2D12However, it also h
Page 26 and 27: ed LED on the maze. Therefore, the
Page 28 and 29: Since the beacon signal needs to co
Page 32 and 33: Figure 31. Pin assignments for Pac-
Page 34 and 35: Table 2. RF signal format for Pac-M
Page 36 and 37: We know that the timer counts at 1
Page 38 and 39: Figure 40. Pin assignments for the
Page 40 and 41: The measurements for the right and
Page 42 and 43: 7.0 MazeThe maze is the area in whi
Page 44 and 45: Table 4. Truth table of the Memory
Page 46 and 47: 8.4 RegulatorsRegulators were added
Page 48 and 49: 9.0 RecommendationsRFIn order to re
Page 50 and 51: 10.0 ConclusionThe design and imple
Page 52 and 53: APPENDIX A: Photo GalleryPac-ManGho
Page 54 and 55: APPENDIX B: PCB LayoutsPac-ManBotto
Page 56 and 57: GhostBottom Layer (PIC, motor, cont
Page 58 and 59: MazeLEDs and sensor circuit
Page 60 and 61: APPENDIX D: Gantt chartWeek 1(May 6
Page 62 and 63: Pac-Man Source Code/***************
Page 64 and 65: }}}next_turn = NONE;turn_ready = 0;
Page 66 and 67: MIN_RIGHT += read_adc();}output_bit
Page 68 and 69: if ( (ob_left > MAX_LEFT) || (ob_ri
Page 70 and 71: Ghost Source Code/*****************
Page 72 and 73: }case S:}go_forward();break;}curren
Page 74 and 75: }if ( walls & SOUTH )return 0;elser
Page 76 and 77: }queue_count = 0, queue_index = 0,
Page 78 and 79: }}}turn_enable = 0;turn_180 = 0;tur
Page 80:
{// Look for Pac-Man's beacon signa
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