50 Pounds of Robot Love

Introduction Sensor Strategies Mechanical Design Electrical Design Software Design Gems of Wisdom About the Team

Software Design For our project, we used both the S12E128 and S12C32 microcontrollers. The E128 handled all sensors and decision making and the C32 controlled all actuators. The E128 gave commands to the C32 using a Serial Peripheral Interface (SPI) datalink. E128 Pseudocode | C32 Pseudocode E128 Code Listing |C32 Code Listing E128 Pseudocode E128 Main Module | SPI-Master Module | Tape Sensor Module | Beacon Sensor Module E128 Main Module Main: Init SPI Init Beacon Sensors Init Timers Enable timers Set prescale to highest resolution Init LEDs Set DDRP to outputs Set PTP LO– turn all LEDs off Init Tape Sensors Init Flash Sensor 1. Wait for a flash 2. Turn clockwise in place 3. Check for 50% duty cycle beacon 4. Stop for 1 sec once pointing at ball dispenser 5. Drive forward blindly for 1 sec 6. Start checking tape sensors for line hit 7. Once line is hit, decide which side of the game board we are on 8. Keep driving forward until robot is approximately centered over tape 9. Turn to get onto the line 10. Begin PI controlled line following 11. Continue until corner of tape 12. Rotate in place to line up rear tape sensors with the line leading towards dispenser 13. Use PI controlled line following in reverse 14. Stop when next to dispenser / rear tape sensors hit a line 15. Move forward until off that line, to give room for button presser 16. Detach front bot 17. Front bot drives along a curved path towards goal #3 based purely on board geometry 18. Stop 19. Turn in place to locate 90% duty cycle beacon 20. Once found, use the difference in strength of signal from the beacon to each of the two analog beacon sensors to drive toward 90 % beacon 21. Continue tracking for about 10 secs; until locked in above goal #3 22. Begin to hit the dispenser button for 1 second every 1.5 seconds. void InitializeLEDPorts(): Set DDRP to all ouputs Set PTP LO– Turn LEDs off void IssueCommand(unsigned char device, unsigned char command): Transfer the device byte through SPI Transfer the command byte through SPI void FollowLine(theta0, x0, direction): Calculate elapsed time using TCNT Calculate theta decay, used to limit memory If on inside left tape, set x = 1 If on inside right tape, set x = -1 If on both inside tapes, set x = 0 If on outside left tape, x = x*2 If on outside right tape, x = x*2 If driving backwards, check if rear tape sensors are on tape. If so, stop following Otherwise, calculate dv, the sum of controlled compensation for heading error and for lateral error. Determine the duty to set each the L and R motors void DebugLEDx (char LEDs): Set PTP to the byte given unsigned char MatchBeaconDutyBW (unsigned char eye, unsigned char duty, char HiBW, char LoBW): If the current duty on the desired eye is within the range of duty – LoBW and duty + highBW, return true. void Detach(void): Send SPI device = DETACH, command = START_UNLATCH Block for a couple seconds with a timer Send SPI device = DETACH, command = STOP_UNLATCH void InitializeFlash(void): Set DDRT to input for flash bit void WaitForFlash(void): Wait until flash bit of PTT goes HI to return SPI Master – E128 Module void SPIM_InitializeSPI(void) Initialize baud rate 47 kHz (256 divisor) Use phase 3 clock Set E128 to Master Enable slave select Set to normal mode Enable SPI unsigned char SPIM_TransferByte(unsigned char) Clear the SPIF flag if it is set Write byteOut to SPIDR Wait for byte to be received Return the received byte Tape Sensor Module Constants OUTSIDE_RIGHT BIT3HI INSIDE_RIGHT BIT2HI INSIDE_LEFT BIT1HI OUTSIDE_LEFT BIT0HI ALL_TAPE (BIT0HI|BIT1HI|BIT2HI|BIT3HI) BACK_LEFT BIT4HI BACK_MIDDLE BIT5HI BACK_RIGHT BIT6HI TAPE_PORT PTU TAPE_PORT_DD DDRU BACK_LEFT_CUTOFF 550 BACK_MID_CUTOFF 550 BACK_RIGHT_CUTOFF 550 void TS_InitializeTapeSensors(void) Set DDRU to input for tape sensors Initialize AD unsigned char TS_GetTape(void) Return the which of the tape sensors are HI. unsigned char TS_GetBackTape(void) Return which analog values for the rear tape sensors are above the defined cutoffs unsigned int TS_GetAnalogValue(char) Return the requested analog value Beacon Sensor Module Constants PERIOD_CHANGE_MAX 25 N_HISTORY 10 void BS_OpenEyes(void) Init timer Enable timer Set to 187.5 kHz clock Capture rising edges on IC4,6 Capture falling edges on IC5,7 Init interrupts Init history Set DutyHistory to all zeros Init AD char BS_GetDuty(char) If there hasn’t been an update in 1 ms, assume the beacon is lost Otherwise, return either DutyLeft or DutyRight as desired char BS_NewDutyArrived(char) Return true if a new duty for this sensor has been received void BS_NewDutyHandled(char) Clear new duty flag for this sensor unsigned int BS_GetAnalog(char) Return the analog signal strength associated with this sensor void interrupt _Vec_tim0ch4 Chan1HI(void) Save current time as last low time Log change in this channel Clear interrupt flag void interrupt _Vec_tim0ch5 Chan1LO(void) Save current time as last high time Calculate duty from difference in last hi and last lo time Take the time average of the last 10 duty readings Log new duty received Clear the interrupt flag void interrupt _Vec_tim0ch6 Chan2HI(void) Save current time as last low time Log change in this channel Clear interrupt flag void interrupt _Vec_tim0ch7 Chan2LO(void) Save current time as last high time Calculate duty from difference in last hi and last lo time Take the time average of the last 10 duty readings Log new duty received Clear the interrupt flag C32 Pseudocode C32 Main Module | Detach Module | DriveMotor Module | SPI Constants | SPI-Slave Module | Switch Motor Module C32 Main Module Main: Initialize SPI Initialize Drive Motor Initialize Detach Motor Initialize Switch Motor Enable Interrupts Repeat Forever: Handle switch motor timer expire Handle new SPI data If received byte is a device Set current device to designated device Available devices: DRIVE – Sets L/R motor directions to preset PWM DRIVE_LEFT_FORWARD – Sets L CW PWM DRIVE_LEFT_REVERSE - Sets L CCW PWM DRIVE_RIGHT_FORWARD – Sets R CCW PWM DRIVE_RIGHT_REVERSE – Sets R CW PWM DETACH – Runs Detach motor CW RELOAD – Runs Switch motor back and forth If received byte is a command Handle the command for the current device Private Functions: void DriveCommand: Takes SPI command byte for device = DRIVE Available commands: TURN_LEFT TURN_RIGHT DRIVE_STRAIGHT STOP REVERSE void DriveLeftForwardCommand: Takes SPI command byte for device = DRIVE_LEFT_FORWARD Available commands Sets Left PWM: DM_SetPWM_Left(command) void DriveLeftReverseCommand: Takes SPI command byte for device = DRIVE_LEFT_REVERSE Available commands Sets Left PWM: DM_SetPWM_Left(-command) void DriveRightForwardCommand: Takes SPI command byte for device = DRIVE_RIGHT_FORWARD Available commands Sets Left PWM: DM_SetPWM_Right(command) void DriveRightReverseCommand: Takes SPI command byte for device = DRIVE_RIGHT_REVERSE Available commands Sets Left PWM: DM_SetPWM_Right(-command) void DetachCommand: Takes SPI command byte for device = DETACH Available commands START_UNLATCH STOP_UNLATCH void ReloadCommand: Takes any command for device = RELOAD as PRESS_BUTTON Detach Module Constants: LATCH PTT UNLATCH BIT2HI LATCH_STOP ~UNLATCH LATCHING_TIMER 0 UNLATCH_TIME 250 Interface Functions: void D_Initialize() Set DDRT to UNLATCH Set LATCH to LATCH_STOP so robot is in one piece void D_Transform() Set LATCH to UNLATCH—pull the latch pin high, driving the latching motor. void D_StopMotor() Set LATCH to LATCH_STOP– pulls that pin low, stopping the motor. DriveMotor Module Constants: Clock_Scale_Value 128 // post scaler. 3 MHz / (128*2) Total_Period_Value 100 // clock cycles per PWM period MS *750 RAMMING_SPEED 30 REVERSE_SPEED -30 INSIDE_TURNING_SPEED -30 OUTSIDE_TURNING_SPEED 30 ON 1 OFF 0 DIR PTAD LEFT_FORWARD BIT0LO RIGHT_FORWARD BIT1LO LEFT_BACKWARD BIT0HI RIGHT_BACKWARD BIT1HI Interface Functions: void DM_Initialize(void) Init AD0 and AD1 to output Init PWM to Clock_Scale_Value Stop the drive motor void DM_UpdateMotors(char, char) Sets left and right duty cycles void DM_TurnRight(void) Sets left to OUTSIDE_TURNING_SPEED Sets right to INSIDE_TURNING_SPEED void DM_TurnLeft(void) Sets right to OUTSIDE_TURNING_SPEED Sets left to INSIDE_TURNING_SPEED void DM_DriveStraight(void) Sets left and right to RAMMING_SPEED void DM_Stop(void) Sets left and right to zero void DM_Reverse(void) Sets left and right to REVERSE_SPEED void DM_SetPWM_Left(char) Sets the left duty void DM_SetPWM_Right(char) Sets the right duty SPI Constants Module – Shared C32 and E128 Contains bit designations for devices and their respective commands. SPI Slave Module – C32 Module Level Vars: unsigned char newData is true if new data has been received unsigned char byteIn stores the received byte Interface Functions: void SPIS_InitializeSPI(void) Init baud rate, clock phase, slave select Enable interrupts Enable SPI Read SPISR and write SPIDR unsigned char SPIS_IsNewData(void) returns newData to indicate whether or not new data has been received void SPIS_ClearDataFlag(void) sets newData to false to indicate that data has been handled unsigned char SPIS_ReadByte(void) returns the stored byte Switch Motor Module Interface Functions: void SM_Initialize(void) Enables PWM chan 3 Sets PWM polarity to 1 Sets PWM clock to 187.5 kHz, then post-scaled Ties PWM to T3 Sets switch motor off Inits a 4ms timer void SM_UpdateMotor(char) Sets the motor duty cycle char SM_NeedsAttention(void) Indicates timer expired void SM_StartPressing(void) Sets state to WAS_PRESSING Clears expired timer Starts new timer Updates motor to forward à stalls pressing the button for 1 sec void SM_BackOff(void) Sets state to WAS_REVERSING Clears expired timer Starts new timer Updates motor to reverse à stalls pressing against robot for 50 ms void SM_Wait(void) Released motor Sets state to WAS_WAITING Clear timer Starts new 3 sec timer