MICROMOUSE MINI-PROJECT

Transcription

1 MICROMOUSE MINI-PROJECT Embedded Systems 1 1 Niall O Keeffe

2 Table Of Contents 1. Introduction AIRAT2 Battery Downloading a program to the AIRAT Downloading To SRAM Downloading To Flash Memory AIRAT2 Hardware Description AIRAT2 LEDs AIRAT2 Buzzer AIRAT2 LCD AIRAT2 Stepper Motors IR LEDs and IR Sensors Analog to Digital Converter (ADC) AIRAT2 Counters Writing Assembly Language Programs for AIRAT Project Ideas...15 Embedded Systems 1 2 Niall O Keeffe

3 1. Introduction The AIRAT2 is a micro-mouse robot that uses the 8051 microcontroller. The microcontroller used is an AT89C51 from Atmel. AIRAT2 contains the following hardware features: - 1. AT89C51 microcontroller 2. Flash memory for code download. This allows the downloaded code to be stored in a non-volatile memory. 3. External SRAM memory for code download. 4. RS-232 interface for serial communication and code download push-button switches 6. LEDs 7. Buzzer 8. 2-line LCD display 9. 2 stepper motors IR LEDs IR sensor pairs that may be used as proximity sensors. 11. An 8-channel Analog to Digital converter bit counters 2. AIRAT2 Battery The AIRAT2 uses two 7.2V NiMH(450mA) packed batteries. One is at the front, and the other is at the back of the robot. A power supply is required to charge the batteries, which have a current limitation function. The two batteries should be connected to the robot (main board) before charging. (1) Set the power supply voltage to 17V and max current to 200 ma. At this setting, the power supply provides 17V up to 200 ma of current output. This is called CV (Constant Voltage) mode. The power supply provides a constant 200 ma even if the outside circuit requires more than 200 ma. This is called CC (Constant Current) mode. Generally, a power supply has LED s to indicate the CV and the CC mode. (2) Connect the provided charging cable to the JP9 port on the main board. (3) Connect the charging cables (RED(+), BLACK(-)) to the power supply(17v, 200mA current limit). Pay attention to the polarities. (4) The charging time depends on the battery s state and the charging current. In the case of totally discharged battery, it will take approximately 3 hours with 200mA charging current. (5) Over charging produces heat. Check the batteries regularly. When the batteries are warm, stop charging. Embedded Systems 1 3 Niall O Keeffe

4 3. Downloading a program to the AIRAT2 The AIRAT2 contains 2 memory spaces that may be used to store the application program: - SRAM for volatile storage Flash memory for non-volatile storage The JsLoader.exe is a file uploader (Windows version) for the AIRAT2 CPU board. It can upload either a hex or binary file. Connect the CPU board to the PC using the provided serial cable and turn on (or reset) the CPU board switch. The board s download/restart mode is activated after reset. Start the JSLoader application and browse to the hex file to download. Press the Transfer option and you are now ready to download code to the board. To use the downloading mode, pull out the JP6 jumper switch. The sections below describe how to download a hex file to the board. Embedded Systems 1 4 Niall O Keeffe

5 3.1 Downloading To SRAM To use the downloading mode, pull out the JP6 jumper switch. To download a file to RAM in the downloading mode, just turn on the board switch or reset the board. To start a file (program) downloading, press the S2 (green) key on the AIRAT2 CPU board after running JsLoade.exe. The downloaded program is executed automatically. To restart the downloaded program in the RAM downloading mode, press the S1 (reset) key and then the S3 (blue) key on the board. The downloaded program is located in the RAM. Therefore it is removed when the board power is turned off. If the user wants to the program to be kept without the power, use the Flash memory downloading mode. To restart the downloaded program in the Flash memory downloading mode, turn the power off and press the JP6 jumper switch, and then turn on the switch. The downloaded program is located in the Flash memory; therefore it is not removed when the power is turned off. If you want to return to the downloading mode, pull out the JP6 jumper. 3.2 Downloading To Flash Memory The PC is now ready for transmission. If the JP6's jumper block is pressed in on the AIRAT2 CPU board pull it out. Turn on the power when the AIRAT2's S3(blue) key is pressed. Then remove your finger from the S3 key. When the S2(green) key is pressed serial downloading begins. Then the transmitting byte is shown on the PC monitor. When transmission is complete, press the jumper block of JP6, press reset button or turn off and on the AIRAT2 CPU board. To restart the downloaded program in the Flash memory downloading mode, turn the power off and press the JP6 jumper switch, and then turn on the switch. The downloaded program is located in the Flash memory; therefore it is not removed when the power is turned off. If you want to return to the downloading mode, pull out the JP6 jumper. Embedded Systems 1 5 Niall O Keeffe

6 4. AIRAT2 Hardware Description 4.1 AIRAT2 LEDs The AIRAT2 has 4 LEDs connected as follows: - Top Board LED P1.5 Bottom board left LED P1.2 Bottom board right LED P1.3 Bottom board front LED P3.4 A logic 0 turns on an LED. 4.2 AIRAT2 Buzzer The AIRAT2 contains a piezo-electric buzzer connected to port pin P1.4. The buzzer will sound when a frequency is output on pin P1.4. Embedded Systems 1 6 Niall O Keeffe

7 4.3 AIRAT2 LCD The unit uses a 2-line LCD display. The LCD is memory mapped in the address range C000H to C3FFH. Address pin A0 is used for the LCD R/W pin and address pin A1 is used for the RS pin. The following addresses should be used to interface to the LCD: - LCD Command Write LCD Data Write C000H C002H The following commands have been defined for the LCD. The first 4 commands should be sent at the start of your program to initialize the display. The SECONDLINE command should be sent to move the cursor to the start of the second line of the display. ;LCD Commands FUNCTIONSET EQU 3BH DISPLAYON EQU 0EH ENTRYMODESET EQU 06H CLEARSCREEN EQU 01H SECONDLINE EQU 0C0H The following subroutine can be used to write a command or data byte to the display. LCD_WRITE: CALL DELAY_5MSEC RET ;allow write operation to complete The following assembly language code can be used to write a command to the LCD interface. MOV DPTR, #LCD_COMMAND_WRITE MOV A, # FUNCTIONSET CALL LCD_WRITE The following assembly language code can be used to write the character A on the LCD display. MOV DPTR, #LCD_DATA_WRITE MOV A, # A CALL LCD_WRITE Embedded Systems 1 7 Niall O Keeffe

8 4.4 AIRAT2 Stepper Motors The AIRAT2 contains 2 stepper motors that operate in half-step mode by default. The motors have a step size of 1.8 degrees. The AIRAT2 contains programmable logic to generate the step sequences for the motors. The 8051 controls the motors using the following signals: - Signal Description Motor Enable P1.5. A logic 0 turns on the motors Right Motor Direction P1.1 Left Motor Direction P1.0 Right Motor Pulse Clock to determine motor speed. This clock is determined by the low to high transition of bit D15 of counter 0 Left Motor Pulse Clock to determine motor speed. This clock is determined by the low to high transition of bit D15 of counter 1 The following steps are required to control the stepper motors: - 1. Configure the motor direction bits. 2. Enable the motor by writing a logic 0 to the motor enable bit. 3. Configure the external counters to generate clocks to pulse the motors. The motors can be stepped at intervals of 5msec. ;**************************************************************** ;Subroutine to drive the motors forward one half resolution ;The motor is driven for 200 * 0.9 degree steps = 180 degrees ;The motor is operating in half-step mode ;The 2 external timers are used to generate the motor clock signal ;The timers will cause the motors to be stepped every 5msec FORWARD_HALF_REV: SETB DIR_MOTOR_R CLR DIR_MOTOR_L MOV R0, #200 ;no. of steps LOAD: CALL RELOAD ;reload counters for 5msec delay WAITF: JB INT0, WAITF DJNZ R0, LOAD RET ;**************************************************************** Embedded Systems 1 8 Niall O Keeffe

9 4.5 IR LEDs and IR Sensors AIRAT contains 6 IR LEDs and 6 IR sensors. The 6 LED and sensor pairs can be used to detect obstacles in 6 different directions. LED-Sensor Pair Direction 0 Left Front 1 Left Side 2 Left 45 Degrees 3 Right 45 Degrees 4 Right Side 5 Right Front Micro Mouse Embedded Systems 1 9 Niall O Keeffe

10 The IR LEDs are connected to a latch that is memory mapped at address DC00H. The LEDs are connected to the lower 6 data bits of the latch output. A logic 1 will turn on a LED. The code below will turn on LED 0 (the front Left IR LED). MOV DPTR, #0DC00H ;turn on front left IR LED MOV A, #01H The outputs from the 6 IR sensors are connected to channels 0 to 5 of the ADC. The next section describes how the ADC may be used to measure the light intensity detected by the IR receivers. Embedded Systems 1 10 Niall O Keeffe

11 4.6 Analog to Digital Converter (ADC) The AIRAT2 contains an 8-channel ADC. The ADC is memory mapped in address range C400H to C7FFH. Channels 0 to 5 of the ADC are used to measure the output signal from the 6 IR receivers. ADC Channel Input Signal 0 Front Left Sensor 1 Left Sensor 2 Left 45 Degree Sensor 3 Right 45 Degree Sensor 4 Right Sensor 5 Front Right Sensor 6 Unused 7 Unused A read from the ADC address will start a new conversion and will return the sample value from the previous conversion. The channel to be converted is specified in the lower 3 address bits. To read from channel 0, read from the ADC base address. To read from channel 2, read from the ADC base address + 2. Two successive reads are required to read an ADC sample. The first read will start the sample and the second read returns the sample. An ADC conversion takes 2.5usec. The code below reads the light intensity from the front left IR sensor. READ_ADC: DELAY1: DELAY2: MOV DPTR, #IR_LED_ADDRESS ;turn on front left IR LED MOV A, #01H ;Delay before reading ADC MOV R0, #100 DJNZ R0, DELAY1 ;Read from ADC channel to start new conversion MOV DPTR, #(ADC_BASE_ADDRESS) MOVX MOV R0, #40 DJNZ R0, DELAY2 ;Do a second read to read value from previous conversion MOV DPTR, #(ADC_BASE_ADDRESS) MOVX MOV R0, A ;turn off IR LED MOV DPTR, #IR_LED_ADDRESS MOV A, # B MOV A, R0 RET Embedded Systems 1 11 Niall O Keeffe

12 4.8 AIRAT2 Counters AIRAT2 contains 2 16-bit count-down counters. The counters are enabled by writing to latch2. A logic 1 enables the timers. The following steps should be used to start the timers: - 1. Disable the counter. (EN = 0) 2. The high byte of the count is written. 3. The low byte of the count is written. 4. Enable the counter (EN = 1) The counters use a 4MHz clock and count down from an initial value. The MSB of the counter is inverted and used to provide the clock for the stepper motors. The pulse outputs are also connected to the relevant 8051 hardware interrupt pin. Pulse0 connects to INTO. Pulse1 connects to INT1. Code to generate a 1msec delay using counter 0. ;Timers TIMER_ENABLE_ADDRESS EQU 0D800H TIMER0_LOW_REGISTER EQU 0C800H TIMER0_HIGH_REGISTER EQU 0CC00H DELAY: ;disable timer MOV DPTR, # TIMER_ENABLE_ADDRESS MOV A, #00H ;write initial value of 0FA0H (1msec) MOV DPTR, # TIMER0_HIGH_REGISTER MOV A, #0FH MOV DPTR, # TIMER0_LOW_REGISTER MOV A, #0A0H MOV DPTR, # TIMER_ENABLE_ADDRESS Embedded Systems 1 12 Niall O Keeffe

13 WAIT: ;enable timer MOV A, #01H ;wait for timer to underflow from 0000H to FFFFH ;on underflow P3.2 (INTO) will go low JB P3.2, WAIT ;disable timer MOV DPTR, # TIMER_ENABLE_ADDRESS MOV A, #00H RET Embedded Systems 1 13 Niall O Keeffe

14 5. Writing Assembly Language Programs for AIRAT2 Ensure that your code is above the interrupt vector space of the Start all programs as follows: - ;********************************** ORG 0H JMP MAIN ORG 35H MAIN: ;********************************** Set your project options to ensure that the Keil tools produce a hex file when you build the project. Embedded Systems 1 14 Niall O Keeffe

15 6. Project Ideas Your mini-project should use some or all of the features described in section 4. The mark awarded will depend on the number of features incorporated and their complexity. Some ideas are: - 1. Drive the micromouse under PC control 2. Get the micromouse to follow a defined route 3. Use the LCD or serial port to provide user feedback during operation 4. Use the LEDs as indicators when turning the micromouse 5. Use the IR detectors to avoid obstacles 6. Use the buzzer for status information e.g. vehicle is reversing Embedded Systems 1 15 Niall O Keeffe