Abstract
The report details the implementation of distance measurement system using the ultrasonic waves. As the human ear’s audible perception range is 20 Hz to 20 kHz, it is insensitive to ultrasonic waves, and hence the ultrasound waves can be used for applications inindustries/vehicles without hindering human activity. They are widely used as range meters and proximity detectors in industries also it can be used in parking assistance system. The distance can be measured using pulse echo and phase measurement method. Here the pulse echo method is used. The measurement unit uses a continuous signal in the transmission frequency range of ultrasonic transducers. The signal is transmitted by an ultrasonic transducer, reflected by an obstacle and received by another transducer where the signal is detected. The time delay of the transmitted and the received signal corresponds to the distance between the system and the obstacle.
1. Introduction
The techniques of distance measurement using ultrasonic in air include continuous wave and pulse echo technique. In the pulse echo method, a burst of pulses is sent through the transmission medium and is reflected by an object kept at specified distance. The time taken for the pulse to propagate from transmitter to receiver is proportional to the distance of object. For contact less measurement of distance, the device has to rely on the target to reflect the pulse back to itself. The target needs to have a proper orientation that is it needs to be perpendicular to the direction of propagation of the pulses. The amplitude of the received signal gets significantly attenuated and is a function of nature of the medium and the distance between the transmitter and target. The pulse echo or time-of-flight method of range measurement is subject to high levels of signal attenuation when used in an air medium, thus limiting its distance range.
2. Design procedure
The circuit has been divided into two divisions.
(i) Digital section- micro controller and LCD display unit with 5volt power supply
(ii) Analog section –
(a) Transmitting side - Ultrasonic transducers, gain amplifier using uA741 CD4066
CMOS analog switch.
(b) Receiving side - TL084 comparator, gain amplifier, voltage limiter.
(c) +15V and -15V power supply.
The overall block diagram is shown in Fig.1.
2.1 Transmitting unit
Switch
An analog switch CD4066 is used to allow the sine wave from function generator to the gain amplifier. The excitation to the Transmitter is given from the Function generator through the switch which can be digitally controlled. As the switch can pass only positive voltages, the 40kHz, 1Vp-p, sine wave from the function generator is given a DC shift of 0.5V.
Microcontroller.
This system of distance measurement does not require large amount of memory, hence a 20 pin 8051 based microcontroller AT89C2051, is chosen as the controller with 12MHz clock. It performs the operation of giving the switching signal, computing the distance, converting the hex value to decimal and then to ASCII to be displayed in the LCD.
Gain Amplifier
As the 40 kHz sine wave cannot be passed through the analog switch 4066, a gain amplifier with level shifter is required. Both are integrated and built using μA741 opamp.
2.2 Receiver unit
Amplifier
The frequency of the received pulse is of 40 kHz which requires amplifiers working at high frequency. TL084 is used, as it has good high frequency gain characteristics. The gain of the amplifier is set to 1000 in two stages with first being 100 and second being 10. The gain is set by taking into account the least magnitude (50mV) of the receiver output when sensing an object at distance of 2 metres.
Comparator
The output signal from the amplifier is passed through the comparator which compares with a reference threshold level to weed out the noises and false triggering. The signal is a series of square pulses as shown in Fig.1 with amplitude of 15 volts. This is passed through the voltagelimiter (zener regulator) to be fed to the microcontroller for counting the pulses.
3. Description
The time of flight method is used for finding the distance between the transmitter and the object. The transmitter sends out a burst of pulses and a receiver detects the reflected echo. The time delay between the corresponding edges of the transmitted and received pulses is measured by microcontroller, this gives the time of flight. Substituting the time delay and the velocity of ultrasound in air (330 metres/second) in the following formula we can determine the distance between the transmitter and the target. Fig.2 shows the transmitted and received pulses.
Distance = Velocity X Elapsed time
The microcontroller closes the switch for duration of 250 microseconds to allow 10 cycles of 40 kHz sine wave. The sine wave varying between 0-1V passes through the switch to the gain amplifier. The level shifter and gain amplifier gives a sine wave with output varying between - 10V and +10V. The transmitter sends out a burst of 10 pulses. As the transducers are directional they are positioned to face the target. Flow chart of the program is given in Fig. 4(a) & 4(b).
The microcontroller with LCD makes it user friendly and can be embedded in a single unit. The circuit has been implemented on bread board and tested for its functionality by varying the distance between the transducer and the target. The target surface needs to be perpendicular to the impinging ultrasound waves. The power level of the signal is too low for long range measurement.
• The range can be considerably increased by using high power drive circuit.
• Using temperature compensation, it can be used over wide temperature range.
• The resolution of the measurement can be improved by incorporating phase shift method along with time of flight method.
• Can be used as parking assistance system in vehicles with high power ultrasonic transmitter.
• The 40 kHz signal can be generated using microcontroller itself which will reduce hardware.
We express our deep gratitude to Prof P. C. Pandey for his timely and valuable guidance for the successful completion of the project. We also like to thank the WEL lab RAs, TAs, and Staff for their continuous support. Doing this work was a really a lot of fun as we could get our hand on the practical applications of electronic principles also it was a very good learning experience as a group.
Time of flight = 950μs
Distance measured = 330 = 0.347 metres
950μs
Fig.2 Transmitted and Received Pulses
Distance measured = 330 = 0.347 metres
950μs
Fig.2 Transmitted and Received Pulses
Microcontroller calculates the distance by the above formula. This distance is twice of the required distance. Hence it is reduced to half and this calculated distance is displayed on the LCD. The LCD is refreshed every 250 milliseconds.
Channel 3 : Output receiver amplifier
Channel 4 : Input pulses to the microcontroller.
Fig. 3 Signals in the receiver section
Channel 4 : Input pulses to the microcontroller.
Fig. 3 Signals in the receiver section
3.1 Firmware description
The microcontroller closes the switch for duration of 250 microseconds to allow 10 cycles of 40 kHz sine wave. The sine wave varying between 0-1V passes through the switch to the gain amplifier. The level shifter and gain amplifier gives a sine wave with output varying between - 10V and +10V. The transmitter sends out a burst of 10 pulses. As the transducers are directional they are positioned to face the target. Flow chart of the program is given in Fig. 4(a) & 4(b).
The microcontroller waits to receive the pulses for a maximum duration of 12 milliseconds. This is the time taken for the ultrasound waves to travel a maximum distance of 4 metres (time of flight gives twice the time taken to traverse a unit distance). If it doesn’t receive the pulses within this time it is considered as absence of object or object out of range. Once the pulses are received the microcontroller counts 10 pulses with a time spacing of 25 microseconds only then the measurement is considered valid and the computation using the formula is implemented. Necessary hex to decimal conversion and decimal to ASCII conversions are performed to display the output of the computation in the LCD. The appendix gives the detailed program with necessary comments for this application.
4. Conclusion
The microcontroller with LCD makes it user friendly and can be embedded in a single unit. The circuit has been implemented on bread board and tested for its functionality by varying the distance between the transducer and the target. The target surface needs to be perpendicular to the impinging ultrasound waves. The power level of the signal is too low for long range measurement.
5. Future Work
• The range can be considerably increased by using high power drive circuit.
• Using temperature compensation, it can be used over wide temperature range.
• The resolution of the measurement can be improved by incorporating phase shift method along with time of flight method.
• Can be used as parking assistance system in vehicles with high power ultrasonic transmitter.
• The 40 kHz signal can be generated using microcontroller itself which will reduce hardware.
6. Acknowledgement
We express our deep gratitude to Prof P. C. Pandey for his timely and valuable guidance for the successful completion of the project. We also like to thank the WEL lab RAs, TAs, and Staff for their continuous support. Doing this work was a really a lot of fun as we could get our hand on the practical applications of electronic principles also it was a very good learning experience as a group.
Circuit Diagram:
(To see the full view Right Click on the the Image and Select "View Image" from it)
Source Code
;*************************************************************************************************************************************************
; FiIRMWARE FOR DISTANCE MEASUREMENT USING ULTRASONIC TRANSDUCER
; BY:ARVIND SINGH
;*************************************************************************************************************************************************
;TYPE : LEVEL 3 - PROGRAM COMPLETED
;FUNCTION : OPENS AND CLOSES THE SWITCH FOR EVERY 250milliseconds AND CHECK FOR RECEIVING
;:PULSES- COMPUTES DISTANCE FROM TIME OF FLIGHT, CONVERTS HEX TO DECIMAL AND; : THEN TO ASCII TO DISPLAY IN LCD. DESCRIPTION FOR EACH SUBROUTINE INS GIVEN IN; : ITS HEADER ;STATUS : TESTED OK ;DATE : 12th NOVEMBER 2010;MICROCONTROLLER : AT89C2051;DESCRIPTION : GIVE THE LCD , LED CONNECTION, RCV-INPUT AS INDCTED IN THE DEFINE MACRO
;*************************************************************************************************************************************************
RCV_INPUT EQU P3.1
SWITCH EQU P3.2
LED EQU P3.3
RS EQU P3.4
EN EQU P3.5
FIRSTFLG EQU 2Eh
TIMER_0_FLAG EQU 2Fh
COUNTER EQU 41h
FIRST_BYTE EQU 42h
SECOND_BYTE EQU 43h
THIRD_BYTE EQU 44h
FOURTH_BYTE EQU 45h
FIFTH_BYTE EQU 46h
SIXTH_BYTE EQU 47h
SEVEN_BYTE EQU 48h
EIGTH_BYTE EQU 49h
ROTA_CNTER_A EQU 4Ah
ROTA_CNTER_B EQU 4Bh
TIMER_1_FLAG EQU 4Ch
DIG1 EQU 4Dh
DIG2 EQU 4Eh
DIG3 EQU 4Fh
BUFFER EQU 50h
OFFSET EQU 05h
NO_OF_PULSES EQU 0Ah
LCD_DATA EQU P1
;**************************************************************************************************************************
; THE MCU STARTS EXECUTING FROM THIS LOCATION AFTER POWER UP
;**************************************************************************************************************************
ORG 0000H
SJMP START
;**************************************************************************************************************************
; THE MCU STARTS EXECUTING FRM THIS LOCATION WHEN THERE IS AN EXTERNAL
; INTERRUPT (INT0)
;**************************************************************************************************************************
ORG 0003H ; INT0
RETI
;**************************************************************************************************************************
; THE MCU STARTS EXECUTING FRM THIS LOCATION WHEN THERE IS A TIMER 0
; INTERRUPT (TIMER0)
;**************************************************************************************************************************
ORG 000BH ; TIMER0
SETB TIMER_0_FLAG
CLR TR0
RETI
;**************************************************************************************************************************
; THE MCU STARTS EXECUTING FRM THIS LOCATION WHEN THERE IS AN EXTERNAL
; INTERRUPT (INT1)
;**************************************************************************************************************************
ORG 0013H ; INT1
RETI
;**************************************************************************************************************************
; THE MCU STARTS EXECUTING FRM THIS LOCATION WHEN THERE IS A TIMER 0
; INTERRUPT (TIMER0)
;**************************************************************************************************************************
ORG 001BH ; TIMER1
SETB TIMER_1_FLAG
CLR TR1
RETI
;**************************************************************************************************************************
; THE MCU STARTS EXECUTING FRM THIS LOCATION WHEN THERE IS A SERIAL
; (RECEIVES) INTERRUPT
;**************************************************************************************************************************
ORG 0023H ; SERIAL
RETI
ORG 0030H
;******************************************************************************************************
; THE PROGRAM STARTS HERE
;******************************************************************************************************
START:
LCALL INIT_INTR
SETB LED ; TURN ON LED
LCALL DISPLAY_LCD
BEGIN:
CLR A
MOV TH1,#0D0h
MOV TL1,#0A6h
CLR TIMER_1_FLAG
SETB TR1 ; START TIMER
SETB SWITCH ; CLOSE THE SWITCH
LCALL DELAY_250MICRO_SEC ; KEEP THE SWITCH CLOSED FOR 250 MICRO SEC
CLR SWITCH ; OPEN THE SWITCH
CPL LED ; TURN ON LED
MOV R7,#NO_OF_PULSES
BACK:
JB TIMER_1_FLAG,BEGINA ; CHECK IF MAXIMUM TIME OF 12 MILLI SECONDS IS OVER
JNB RCV_INPUT,BACK ; WAIT FOR THE RECIVING PULSE
CLR TR1 ; STOP DISTANCE MEASUREMENT TIMER
DEC R7
BACKB:
MOV TH0,#0FFh
MOV TL0,#0E5h ; CONFIGURE DOWN COUNTER FOR 25 MICRO SEC
SETB TR0 ; START COUNT DOWN TIMER
CLR TIMER_0_FLAG
BACKA:
JB TIMER_0_FLAG,BEGIN ; CHECK IF 25 MICRO SECONDS IS OVER OR NOT
JNB RCV_INPUT,BACKA ; WAIT FOR THE RECIVING PULSE
CLR TR0
DJNZ R7,BACKB
LCALL PROCESS
JB FIRSTFLG,UPDATE
LCALL DISPLAY_LCD2 ; DISPLAY THE TME IN HEX
SETB FIRSTFLG
SJMP CONTINUE
UPDATE:
LCALL UPDATE_DATA
CONTINUE:
LCALL DELAY_1_SEC ; WAIT FOR ONE SECOND
SJMP BEGIN
BEGINA:
LCALL NO_PULSE_RCVD
CLR FIRSTFLG
LJMP BEGIN
;******************************************************************************************************
; THE PROGRAM ENDS HERE
;******************************************************************************************************
PROCESS:
MOV R0,TH1
MOV R1,TL1
MOV R2,#0D0h
MOV R3,#0A6h
LCALL SUBTRACT
LCALL DIVI
MOV R2,#01h
MOV R3,#4Ah
LCALL MUL_16BIT
MOV A,R5
MOV DIG3,A
MOV A,R6
MOV DIG2,A
MOV A,R7
MOV DIG1,A
LCALL HEX2DEC
LCALL CONV_2_ASCII ; CONVERT THE CONTENTS OF THE TIMER TO ASCII
RET
;******************************************************************************************************
; INTITIALIZATION ROUTINE
;******************************************************************************************************
INIT_INTR:
MOV IE,#8Ah
MOV TMOD,#11h ; TIMER 0 IN 16 BIT TIMER MODE , TIMER 1 IN 16 BIT TIMER MODE
CLR A
MOV TH0,A
MOV TL0,A
CLR TR0
CLR TR1
MOV P1,#00H
MOV P3,#02H
CLR FIRSTFLG
RET
;**************************************************************************************************************************
; DSIPLAY THE DISTANCE
;**************************************************************************************************************************
DISPLAY_LCD2:
LCALL CLEAR_LCD
MOV DPTR,#LINE3
LCALL LINE1_DATA
MOV DPTR,#LINE4
MOV COUNTER,#10h
MOV R1,#BUFFER
LOOP3:
CLR A
MOVC A,@A+DPTR
MOV @R1,A
INC DPTR
INC R1
DJNZ COUNTER,LOOP3
LCALL LOAD_DATA
LCALL DATA_FRM_BUFFER
RET
;**************************************************************************************************************************
; DSIPLAY NO PULSE RECEIVED
;**************************************************************************************************************************
NO_PULSE_RCVD:
LCALL CLEAR_LCD
MOV DPTR,#NOPULSE
LCALL LINE1_DATA
MOV DPTR,#NOPULSEA
LCALL LINE2_DATA
RET
;**************************************************************************************************************************
; LCD TEST - THIS ROUTINE IS USED FOR TESTING THE LCD. THE FUNCTIONS
; FOLLOWING THE ROUTINE ARE SUBROUTINES USED IN THE LED TESTING ROUTINES
;**************************************************************************************************************************
DISPLAY_LCD:
LCALL LCD_INIT
LCALL CLEAR_LCD
MOV DPTR,#LINE1
LCALL LINE1_DATA
MOV DPTR,#LINE2
LCALL LINE2_DATA
RET
;**************************************************************************************************************************
; PRINTING THE LINE 1 DATA
;**************************************************************************************************************************
LINE1_DATA:
MOV COUNTER,#10h
ALL_DATA:
CLR A
MOVC A,@A+DPTR
INC DPTR
LCALL DATAWRT
DJNZ COUNTER,ALL_DATA
RET
;**************************************************************************************************************************
; PRINTING THE LINE 2 DATA
;**************************************************************************************************************************
LINE2_DATA:
MOV A,#0C0h ; LINE 2 STARTS FROM C0h
LCALL COMNWRT
MOV COUNTER,#10h
AL_DATA:
CLR A
MOVC A,@A+DPTR
INC DPTR
LCALL DATAWRT
DJNZ COUNTER,AL_DATA
RET
;**************************************************************************************************************************
; WRITING THE DATA FROM THE BUFFER TO THE LCD'S SECOND LINE
;**************************************************************************************************************************
DATA_FRM_BUFFER:
MOV A,#0C0h ; LINE 2 STARTS FROM C0h
LCALL COMNWRT
MOV COUNTER,#10h
MOV R0,#BUFFER
DATA_BUF:
MOV A,@R0
LCALL DATAWRT
INC R0
DJNZ COUNTER,DATA_BUF
RET
;**************************************************************************************************************************
; LOAD THE DATA FROM THE TIMER TO THE BUFFER
;**************************************************************************************************************************
LOAD_DATA:
MOV A,#OFFSET
MOV R0,#BUFFER
ADD A,R0
MOV R0,A
MOV A,SECOND_BYTE
MOV @R0,A
INC R0
MOV A,THIRD_BYTE
MOV @R0,A
INC R0
MOV A,FOURTH_BYTE
MOV @R0,A
INC R0
MOV A,#'.'
MOV @R0,A
INC R0
MOV A,FIFTH_BYTE
MOV @R0,A
INC R0
MOV A,SIXTH_BYTE
MOV @R0,A
INC R0
MOV A,SEVEN_BYTE
MOV @R0,A
INC R0
RET
;*******************************************************
; CONVERT TO ASCII
;*******************************************************
CONV_2_ASCII:
MOV A,R0
ANL A,#0Fh
MOV DPTR,#ASCII
MOVC A,@A+DPTR
MOV FIRST_BYTE,A
MOV A,R1
ANL A,#0Fh
MOV DPTR,#ASCII
MOVC A,@A+DPTR
MOV SECOND_BYTE,A
MOV A,R2
ANL A,#0Fh
MOV DPTR,#ASCII
MOVC A,@A+DPTR
MOV THIRD_BYTE,A
MOV A,R3
ANL A,#0Fh
MOV DPTR,#ASCII
MOVC A,@A+DPTR
MOV FOURTH_BYTE,A
MOV A,R4
ANL A,#0Fh
MOV DPTR,#ASCII
MOVC A,@A+DPTR
MOV FIFTH_BYTE,A
MOV A,R5
ANL A,#0Fh
MOV DPTR,#ASCII
MOVC A,@A+DPTR
MOV SIXTH_BYTE,A
MOV A,R6
ANL A,#0Fh
MOV DPTR,#ASCII
MOVC A,@A+DPTR
MOV SEVEN_BYTE,A
MOV A,R7
ANL A,#0Fh
MOV DPTR,#ASCII
MOVC A,@A+DPTR
MOV EIGTH_BYTE,A
RET
;*************************************************************
; INITIALIZATION ROUTINE FOR LCD
;*************************************************************
UPDATE_DATA:
MOV A,#0C5h ; LINE 2 STARTS FROM C0h
LCALL COMNWRT
MOV A,SECOND_BYTE
LCALL DATAWRT
MOV A,THIRD_BYTE
LCALL DATAWRT
MOV A,FOURTH_BYTE
LCALL DATAWRT
MOV A,#'.'
LCALL DATAWRT
MOV A,FIFTH_BYTE
LCALL DATAWRT
MOV A,SIXTH_BYTE
LCALL DATAWRT
MOV A,SEVEN_BYTE
LCALL DATAWRT
RET
;*************************************************************
; INITIALIZATION ROUTINE FOR LCD
;*************************************************************
LCD_INIT:
MOV A,#38H
LCALL COMNWRT
MOV A,#0EH
LCALL COMNWRT
MOV A,#06H
LCALL COMNWRT
RET
;*************************************************************
; CLEARING THE LCD
;*************************************************************
CLEAR_LCD:
CLR RS
MOV A,#01h
LCALL ROTATE
MOV LCD_DATA,A
SETB EN
CLR EN
LCALL DELAY_25MS
RET
;*************************************************************
; ROUTINE TO SEND DATA
;*************************************************************
DATAWRT:
SETB RS
LCALL ROTATE
MOV LCD_DATA,A
SETB EN
CLR EN
LCALL DELAY_25MS
RET
;*************************************************************
; ROUTINE TO SEND COMMAND
;*************************************************************
COMNWRT:
CLR RS
LCALL ROTATE
MOV LCD_DATA,A
SETB EN
CLR EN
LCALL DELAY_25MS
RET
;*************************************************************
; ROUTINE TO ROTATE THE BITS
;*************************************************************
ROTATE:
MOV ROTA_CNTER_A,A
MOV A,ROTA_CNTER_A
MOV C,ACC.7
MOV A,ROTA_CNTER_B
MOV ACC.0,C
MOV ROTA_CNTER_B,A
MOV A,ROTA_CNTER_A
MOV C,ACC.6
MOV A,ROTA_CNTER_B
MOV ACC.1,C
MOV ROTA_CNTER_B,A
MOV A,ROTA_CNTER_A
MOV C,ACC.5
MOV A,ROTA_CNTER_B
MOV ACC.2,C
MOV ROTA_CNTER_B,A
MOV A,ROTA_CNTER_A
MOV C,ACC.4
MOV A,ROTA_CNTER_B
MOV ACC.3,C
MOV ROTA_CNTER_B,A
MOV A,ROTA_CNTER_A
MOV C,ACC.3
MOV A,ROTA_CNTER_B
MOV ACC.4,C
MOV ROTA_CNTER_B,A
MOV A,ROTA_CNTER_A
MOV C,ACC.2
MOV A,ROTA_CNTER_B
MOV ACC.5,C
MOV ROTA_CNTER_B,A
MOV A,ROTA_CNTER_A
MOV C,ACC.1
MOV A,ROTA_CNTER_B
MOV ACC.6,C
MOV ROTA_CNTER_B,A
MOV A,ROTA_CNTER_A
MOV C,ACC.0
MOV A,ROTA_CNTER_B
MOV ACC.7,C
MOV ROTA_CNTER_B,A
RET
;*******************************************************
; SUBROUTINE FOR 1 SECOND DELAY
;*******************************************************
DELAY_1_SEC:
MOV R0,#10
LOOP:
MOV TH0,#3Ch
MOV TL0,#0AFh
CLR TIMER_0_FLAG
SETB TR0
JNB TIMER_0_FLAG,$
DJNZ R0,LOOP
RET
;*******************************************************
; SUBROUTINE FOR 2.5 MILLISECOND SECOND
;*******************************************************
DELAY_250MICRO_SEC:
MOV TH0,#0FFh
MOV TL0,#05h
CLR TIMER_0_FLAG
SETB TR0
JNB TIMER_0_FLAG,$
RET
;*************************************************************
; A DELAY OF 25 milliseconds
;*************************************************************
DELAY_25MS:
MOV TH0,#1Eh
MOV TL0,#57h
CLR TIMER_0_FLAG
SETB TR0
JNB TIMER_0_FLAG,$
RET
;*******************************************************
; R2 R3 -
; R0 R1
; --------
; R0 R1
;*******************************************************
SUBTRACT:
CLR C
MOV A,R1
SUBB A,R3
MOV R1,A
MOV A,R0
SUBB A,R2
MOV R0,A
RET
;*********************************************************************************
;MSB-> R0 R1 DIVIDEND
; R2 DIVISOR
;MSB-> R0 R1 RESULT
;*********************************************************************************
DIVI:
CLR C
MOV A,R0
RRC A
MOV R0,A
MOV A,R1
RR A
MOV ACC.7,C
MOV R1,A
RET
;************************************************************************
;MSB-> R0 R1 MULTIPLICAND
; R2 R3 MULTIPLIER
;MSB-> R4 R5 R6 R7 RESULT
;************************************************************************
MUL_16BIT:
CLR A
MOV R4,A
MOV R5,A
MOV R6,A
MOV R7,A
CLR C
MOV A,R1
MOV B,R3
MUL AB
MOV R7,A
MOV R6,B
MOV A,R0
MOV B,R3
MUL AB
ADD A,R6
MOV R6,A
MOV A,B
ADDC A,R5
MOV R5,A
MOV A,R1
MOV B,R2
MUL AB
ADD A,R6
MOV R6,A
MOV A,B
ADDC A,R5
MOV R5,A
MOV A,R0
MOV B,R2
MUL AB
ADDC A,R5
MOV R5,A
MOV A,B
ADDC A,R4
MOV R4,A
RET
;************************************************************************
; HEX TO DECIMAL CONVERSION ROUTINE
; DIG3 ;MSB
; DIG2
; DIG1 ;LSB
; R0 R1 R2 R3 R4 R5 R6 R7 RESULT
;************************************************************************
HEX2DEC:
MOV R0,#00H ; R7
MOV R1,#00H ; R6
MOV R2,#00H ; R5
MOV R3,#00H ; R0
MOV R4,#00H ; R1
MOV R5,#00H ; R2
MOV R6,#00H ; R3
MOV R7,#00H ; R4
FIRSTA:
CLR C
MOV A,DIG1
SUBB A,#0AH
MOV DIG1,A
JC OUT
OUTB:
INC R6
CJNE R6,#0AH,FIRS
MOV R6,#00H
INC R5
CJNE R5,#0AH,FIRT
MOV R5,#00H
INC R4
CJNE R4,#0AH,FIRU
MOV R4,#00H
INC R3
CJNE R3,#0AH,FIRA
MOV R3,#00H
INC R2
CJNE R2,#0AH,FIRB
MOV R2,#00H
INC R1
CJNE R1,#0AH,FIRC
MOV R1,#00H
INC R0
JMP FIRST
FIRST:
LJMP FIRSTA
FIRS:
JC FIRST
INC R5
CJNE R5,#0AH,FIRT
MOV A,R6
SUBB A,#09H
MOV R6,A
JMP FIRST
FIRT:
JC FIRST
INC R4
CJNE R4,#0AH,FIRU
MOV A,R5
SUBB A,#09H
MOV R5,A
LJMP FIRST
FIRU:
JC FIRST
INC R3
MOV A,R4
SUBB A,#09H
MOV R4,A
LJMP FIRST
FIRA:
JC FIRST
INC R2
MOV A,R3
SUBB A,#09H
MOV R3,A
LJMP FIRST
FIRB:
JC FIRST
INC R1
MOV A,R2
SUBB A,#09H
MOV R2,A
LJMP FIRST
FIRC:
JC FIRST
INC R0
MOV A,R1
SUBB A,#09H
MOV R1,A
LJMP FIRST
OUTBA:
LJMP OUTB
OUT:
CLR C
MOV A,DIG2
SUBB A,#01H
MOV DIG2,A
JNC OUTB
CLR C
MOV A,DIG3
SUBB A,#01H
MOV DIG3,A
JNC OUTBA
MOV A,DIG1
ADD A,#0AH
MOV R7,A
RET
LINE1: DB ' Hi ALL !!!! '
LINE2: DB ' HAVE A GOOD DAY'
LINE3: DB ' Dist Measured '
LINE4: DB ' . cms '
NOPULSE: DB ' NO PULSE '
NOPULSEA: DB ' RECEIVED !!! '
ASCII: DB '0123456789ABCDEF'
END
; FiIRMWARE FOR DISTANCE MEASUREMENT USING ULTRASONIC TRANSDUCER
; BY:ARVIND SINGH
;*************************************************************************************************************************************************
;TYPE : LEVEL 3 - PROGRAM COMPLETED
;FUNCTION : OPENS AND CLOSES THE SWITCH FOR EVERY 250milliseconds AND CHECK FOR RECEIVING
;:PULSES- COMPUTES DISTANCE FROM TIME OF FLIGHT, CONVERTS HEX TO DECIMAL AND; : THEN TO ASCII TO DISPLAY IN LCD. DESCRIPTION FOR EACH SUBROUTINE INS GIVEN IN; : ITS HEADER ;STATUS : TESTED OK ;DATE : 12th NOVEMBER 2010;MICROCONTROLLER : AT89C2051;DESCRIPTION : GIVE THE LCD , LED CONNECTION, RCV-INPUT AS INDCTED IN THE DEFINE MACRO
;*************************************************************************************************************************************************
RCV_INPUT EQU P3.1
SWITCH EQU P3.2
LED EQU P3.3
RS EQU P3.4
EN EQU P3.5
FIRSTFLG EQU 2Eh
TIMER_0_FLAG EQU 2Fh
COUNTER EQU 41h
FIRST_BYTE EQU 42h
SECOND_BYTE EQU 43h
THIRD_BYTE EQU 44h
FOURTH_BYTE EQU 45h
FIFTH_BYTE EQU 46h
SIXTH_BYTE EQU 47h
SEVEN_BYTE EQU 48h
EIGTH_BYTE EQU 49h
ROTA_CNTER_A EQU 4Ah
ROTA_CNTER_B EQU 4Bh
TIMER_1_FLAG EQU 4Ch
DIG1 EQU 4Dh
DIG2 EQU 4Eh
DIG3 EQU 4Fh
BUFFER EQU 50h
OFFSET EQU 05h
NO_OF_PULSES EQU 0Ah
LCD_DATA EQU P1
;**************************************************************************************************************************
; THE MCU STARTS EXECUTING FROM THIS LOCATION AFTER POWER UP
;**************************************************************************************************************************
ORG 0000H
SJMP START
;**************************************************************************************************************************
; THE MCU STARTS EXECUTING FRM THIS LOCATION WHEN THERE IS AN EXTERNAL
; INTERRUPT (INT0)
;**************************************************************************************************************************
ORG 0003H ; INT0
RETI
;**************************************************************************************************************************
; THE MCU STARTS EXECUTING FRM THIS LOCATION WHEN THERE IS A TIMER 0
; INTERRUPT (TIMER0)
;**************************************************************************************************************************
ORG 000BH ; TIMER0
SETB TIMER_0_FLAG
CLR TR0
RETI
;**************************************************************************************************************************
; THE MCU STARTS EXECUTING FRM THIS LOCATION WHEN THERE IS AN EXTERNAL
; INTERRUPT (INT1)
;**************************************************************************************************************************
ORG 0013H ; INT1
RETI
;**************************************************************************************************************************
; THE MCU STARTS EXECUTING FRM THIS LOCATION WHEN THERE IS A TIMER 0
; INTERRUPT (TIMER0)
;**************************************************************************************************************************
ORG 001BH ; TIMER1
SETB TIMER_1_FLAG
CLR TR1
RETI
;**************************************************************************************************************************
; THE MCU STARTS EXECUTING FRM THIS LOCATION WHEN THERE IS A SERIAL
; (RECEIVES) INTERRUPT
;**************************************************************************************************************************
ORG 0023H ; SERIAL
RETI
ORG 0030H
;******************************************************************************************************
; THE PROGRAM STARTS HERE
;******************************************************************************************************
START:
LCALL INIT_INTR
SETB LED ; TURN ON LED
LCALL DISPLAY_LCD
BEGIN:
CLR A
MOV TH1,#0D0h
MOV TL1,#0A6h
CLR TIMER_1_FLAG
SETB TR1 ; START TIMER
SETB SWITCH ; CLOSE THE SWITCH
LCALL DELAY_250MICRO_SEC ; KEEP THE SWITCH CLOSED FOR 250 MICRO SEC
CLR SWITCH ; OPEN THE SWITCH
CPL LED ; TURN ON LED
MOV R7,#NO_OF_PULSES
BACK:
JB TIMER_1_FLAG,BEGINA ; CHECK IF MAXIMUM TIME OF 12 MILLI SECONDS IS OVER
JNB RCV_INPUT,BACK ; WAIT FOR THE RECIVING PULSE
CLR TR1 ; STOP DISTANCE MEASUREMENT TIMER
DEC R7
BACKB:
MOV TH0,#0FFh
MOV TL0,#0E5h ; CONFIGURE DOWN COUNTER FOR 25 MICRO SEC
SETB TR0 ; START COUNT DOWN TIMER
CLR TIMER_0_FLAG
BACKA:
JB TIMER_0_FLAG,BEGIN ; CHECK IF 25 MICRO SECONDS IS OVER OR NOT
JNB RCV_INPUT,BACKA ; WAIT FOR THE RECIVING PULSE
CLR TR0
DJNZ R7,BACKB
LCALL PROCESS
JB FIRSTFLG,UPDATE
LCALL DISPLAY_LCD2 ; DISPLAY THE TME IN HEX
SETB FIRSTFLG
SJMP CONTINUE
UPDATE:
LCALL UPDATE_DATA
CONTINUE:
LCALL DELAY_1_SEC ; WAIT FOR ONE SECOND
SJMP BEGIN
BEGINA:
LCALL NO_PULSE_RCVD
CLR FIRSTFLG
LJMP BEGIN
;******************************************************************************************************
; THE PROGRAM ENDS HERE
;******************************************************************************************************
PROCESS:
MOV R0,TH1
MOV R1,TL1
MOV R2,#0D0h
MOV R3,#0A6h
LCALL SUBTRACT
LCALL DIVI
MOV R2,#01h
MOV R3,#4Ah
LCALL MUL_16BIT
MOV A,R5
MOV DIG3,A
MOV A,R6
MOV DIG2,A
MOV A,R7
MOV DIG1,A
LCALL HEX2DEC
LCALL CONV_2_ASCII ; CONVERT THE CONTENTS OF THE TIMER TO ASCII
RET
;******************************************************************************************************
; INTITIALIZATION ROUTINE
;******************************************************************************************************
INIT_INTR:
MOV IE,#8Ah
MOV TMOD,#11h ; TIMER 0 IN 16 BIT TIMER MODE , TIMER 1 IN 16 BIT TIMER MODE
CLR A
MOV TH0,A
MOV TL0,A
CLR TR0
CLR TR1
MOV P1,#00H
MOV P3,#02H
CLR FIRSTFLG
RET
;**************************************************************************************************************************
; DSIPLAY THE DISTANCE
;**************************************************************************************************************************
DISPLAY_LCD2:
LCALL CLEAR_LCD
MOV DPTR,#LINE3
LCALL LINE1_DATA
MOV DPTR,#LINE4
MOV COUNTER,#10h
MOV R1,#BUFFER
LOOP3:
CLR A
MOVC A,@A+DPTR
MOV @R1,A
INC DPTR
INC R1
DJNZ COUNTER,LOOP3
LCALL LOAD_DATA
LCALL DATA_FRM_BUFFER
RET
;**************************************************************************************************************************
; DSIPLAY NO PULSE RECEIVED
;**************************************************************************************************************************
NO_PULSE_RCVD:
LCALL CLEAR_LCD
MOV DPTR,#NOPULSE
LCALL LINE1_DATA
MOV DPTR,#NOPULSEA
LCALL LINE2_DATA
RET
;**************************************************************************************************************************
; LCD TEST - THIS ROUTINE IS USED FOR TESTING THE LCD. THE FUNCTIONS
; FOLLOWING THE ROUTINE ARE SUBROUTINES USED IN THE LED TESTING ROUTINES
;**************************************************************************************************************************
DISPLAY_LCD:
LCALL LCD_INIT
LCALL CLEAR_LCD
MOV DPTR,#LINE1
LCALL LINE1_DATA
MOV DPTR,#LINE2
LCALL LINE2_DATA
RET
;**************************************************************************************************************************
; PRINTING THE LINE 1 DATA
;**************************************************************************************************************************
LINE1_DATA:
MOV COUNTER,#10h
ALL_DATA:
CLR A
MOVC A,@A+DPTR
INC DPTR
LCALL DATAWRT
DJNZ COUNTER,ALL_DATA
RET
;**************************************************************************************************************************
; PRINTING THE LINE 2 DATA
;**************************************************************************************************************************
LINE2_DATA:
MOV A,#0C0h ; LINE 2 STARTS FROM C0h
LCALL COMNWRT
MOV COUNTER,#10h
AL_DATA:
CLR A
MOVC A,@A+DPTR
INC DPTR
LCALL DATAWRT
DJNZ COUNTER,AL_DATA
RET
;**************************************************************************************************************************
; WRITING THE DATA FROM THE BUFFER TO THE LCD'S SECOND LINE
;**************************************************************************************************************************
DATA_FRM_BUFFER:
MOV A,#0C0h ; LINE 2 STARTS FROM C0h
LCALL COMNWRT
MOV COUNTER,#10h
MOV R0,#BUFFER
DATA_BUF:
MOV A,@R0
LCALL DATAWRT
INC R0
DJNZ COUNTER,DATA_BUF
RET
;**************************************************************************************************************************
; LOAD THE DATA FROM THE TIMER TO THE BUFFER
;**************************************************************************************************************************
LOAD_DATA:
MOV A,#OFFSET
MOV R0,#BUFFER
ADD A,R0
MOV R0,A
MOV A,SECOND_BYTE
MOV @R0,A
INC R0
MOV A,THIRD_BYTE
MOV @R0,A
INC R0
MOV A,FOURTH_BYTE
MOV @R0,A
INC R0
MOV A,#'.'
MOV @R0,A
INC R0
MOV A,FIFTH_BYTE
MOV @R0,A
INC R0
MOV A,SIXTH_BYTE
MOV @R0,A
INC R0
MOV A,SEVEN_BYTE
MOV @R0,A
INC R0
RET
;*******************************************************
; CONVERT TO ASCII
;*******************************************************
CONV_2_ASCII:
MOV A,R0
ANL A,#0Fh
MOV DPTR,#ASCII
MOVC A,@A+DPTR
MOV FIRST_BYTE,A
MOV A,R1
ANL A,#0Fh
MOV DPTR,#ASCII
MOVC A,@A+DPTR
MOV SECOND_BYTE,A
MOV A,R2
ANL A,#0Fh
MOV DPTR,#ASCII
MOVC A,@A+DPTR
MOV THIRD_BYTE,A
MOV A,R3
ANL A,#0Fh
MOV DPTR,#ASCII
MOVC A,@A+DPTR
MOV FOURTH_BYTE,A
MOV A,R4
ANL A,#0Fh
MOV DPTR,#ASCII
MOVC A,@A+DPTR
MOV FIFTH_BYTE,A
MOV A,R5
ANL A,#0Fh
MOV DPTR,#ASCII
MOVC A,@A+DPTR
MOV SIXTH_BYTE,A
MOV A,R6
ANL A,#0Fh
MOV DPTR,#ASCII
MOVC A,@A+DPTR
MOV SEVEN_BYTE,A
MOV A,R7
ANL A,#0Fh
MOV DPTR,#ASCII
MOVC A,@A+DPTR
MOV EIGTH_BYTE,A
RET
;*************************************************************
; INITIALIZATION ROUTINE FOR LCD
;*************************************************************
UPDATE_DATA:
MOV A,#0C5h ; LINE 2 STARTS FROM C0h
LCALL COMNWRT
MOV A,SECOND_BYTE
LCALL DATAWRT
MOV A,THIRD_BYTE
LCALL DATAWRT
MOV A,FOURTH_BYTE
LCALL DATAWRT
MOV A,#'.'
LCALL DATAWRT
MOV A,FIFTH_BYTE
LCALL DATAWRT
MOV A,SIXTH_BYTE
LCALL DATAWRT
MOV A,SEVEN_BYTE
LCALL DATAWRT
RET
;*************************************************************
; INITIALIZATION ROUTINE FOR LCD
;*************************************************************
LCD_INIT:
MOV A,#38H
LCALL COMNWRT
MOV A,#0EH
LCALL COMNWRT
MOV A,#06H
LCALL COMNWRT
RET
;*************************************************************
; CLEARING THE LCD
;*************************************************************
CLEAR_LCD:
CLR RS
MOV A,#01h
LCALL ROTATE
MOV LCD_DATA,A
SETB EN
CLR EN
LCALL DELAY_25MS
RET
;*************************************************************
; ROUTINE TO SEND DATA
;*************************************************************
DATAWRT:
SETB RS
LCALL ROTATE
MOV LCD_DATA,A
SETB EN
CLR EN
LCALL DELAY_25MS
RET
;*************************************************************
; ROUTINE TO SEND COMMAND
;*************************************************************
COMNWRT:
CLR RS
LCALL ROTATE
MOV LCD_DATA,A
SETB EN
CLR EN
LCALL DELAY_25MS
RET
;*************************************************************
; ROUTINE TO ROTATE THE BITS
;*************************************************************
ROTATE:
MOV ROTA_CNTER_A,A
MOV A,ROTA_CNTER_A
MOV C,ACC.7
MOV A,ROTA_CNTER_B
MOV ACC.0,C
MOV ROTA_CNTER_B,A
MOV A,ROTA_CNTER_A
MOV C,ACC.6
MOV A,ROTA_CNTER_B
MOV ACC.1,C
MOV ROTA_CNTER_B,A
MOV A,ROTA_CNTER_A
MOV C,ACC.5
MOV A,ROTA_CNTER_B
MOV ACC.2,C
MOV ROTA_CNTER_B,A
MOV A,ROTA_CNTER_A
MOV C,ACC.4
MOV A,ROTA_CNTER_B
MOV ACC.3,C
MOV ROTA_CNTER_B,A
MOV A,ROTA_CNTER_A
MOV C,ACC.3
MOV A,ROTA_CNTER_B
MOV ACC.4,C
MOV ROTA_CNTER_B,A
MOV A,ROTA_CNTER_A
MOV C,ACC.2
MOV A,ROTA_CNTER_B
MOV ACC.5,C
MOV ROTA_CNTER_B,A
MOV A,ROTA_CNTER_A
MOV C,ACC.1
MOV A,ROTA_CNTER_B
MOV ACC.6,C
MOV ROTA_CNTER_B,A
MOV A,ROTA_CNTER_A
MOV C,ACC.0
MOV A,ROTA_CNTER_B
MOV ACC.7,C
MOV ROTA_CNTER_B,A
RET
;*******************************************************
; SUBROUTINE FOR 1 SECOND DELAY
;*******************************************************
DELAY_1_SEC:
MOV R0,#10
LOOP:
MOV TH0,#3Ch
MOV TL0,#0AFh
CLR TIMER_0_FLAG
SETB TR0
JNB TIMER_0_FLAG,$
DJNZ R0,LOOP
RET
;*******************************************************
; SUBROUTINE FOR 2.5 MILLISECOND SECOND
;*******************************************************
DELAY_250MICRO_SEC:
MOV TH0,#0FFh
MOV TL0,#05h
CLR TIMER_0_FLAG
SETB TR0
JNB TIMER_0_FLAG,$
RET
;*************************************************************
; A DELAY OF 25 milliseconds
;*************************************************************
DELAY_25MS:
MOV TH0,#1Eh
MOV TL0,#57h
CLR TIMER_0_FLAG
SETB TR0
JNB TIMER_0_FLAG,$
RET
;*******************************************************
; R2 R3 -
; R0 R1
; --------
; R0 R1
;*******************************************************
SUBTRACT:
CLR C
MOV A,R1
SUBB A,R3
MOV R1,A
MOV A,R0
SUBB A,R2
MOV R0,A
RET
;*********************************************************************************
;MSB-> R0 R1 DIVIDEND
; R2 DIVISOR
;MSB-> R0 R1 RESULT
;*********************************************************************************
DIVI:
CLR C
MOV A,R0
RRC A
MOV R0,A
MOV A,R1
RR A
MOV ACC.7,C
MOV R1,A
RET
;************************************************************************
;MSB-> R0 R1 MULTIPLICAND
; R2 R3 MULTIPLIER
;MSB-> R4 R5 R6 R7 RESULT
;************************************************************************
MUL_16BIT:
CLR A
MOV R4,A
MOV R5,A
MOV R6,A
MOV R7,A
CLR C
MOV A,R1
MOV B,R3
MUL AB
MOV R7,A
MOV R6,B
MOV A,R0
MOV B,R3
MUL AB
ADD A,R6
MOV R6,A
MOV A,B
ADDC A,R5
MOV R5,A
MOV A,R1
MOV B,R2
MUL AB
ADD A,R6
MOV R6,A
MOV A,B
ADDC A,R5
MOV R5,A
MOV A,R0
MOV B,R2
MUL AB
ADDC A,R5
MOV R5,A
MOV A,B
ADDC A,R4
MOV R4,A
RET
;************************************************************************
; HEX TO DECIMAL CONVERSION ROUTINE
; DIG3 ;MSB
; DIG2
; DIG1 ;LSB
; R0 R1 R2 R3 R4 R5 R6 R7 RESULT
;************************************************************************
HEX2DEC:
MOV R0,#00H ; R7
MOV R1,#00H ; R6
MOV R2,#00H ; R5
MOV R3,#00H ; R0
MOV R4,#00H ; R1
MOV R5,#00H ; R2
MOV R6,#00H ; R3
MOV R7,#00H ; R4
FIRSTA:
CLR C
MOV A,DIG1
SUBB A,#0AH
MOV DIG1,A
JC OUT
OUTB:
INC R6
CJNE R6,#0AH,FIRS
MOV R6,#00H
INC R5
CJNE R5,#0AH,FIRT
MOV R5,#00H
INC R4
CJNE R4,#0AH,FIRU
MOV R4,#00H
INC R3
CJNE R3,#0AH,FIRA
MOV R3,#00H
INC R2
CJNE R2,#0AH,FIRB
MOV R2,#00H
INC R1
CJNE R1,#0AH,FIRC
MOV R1,#00H
INC R0
JMP FIRST
FIRST:
LJMP FIRSTA
FIRS:
JC FIRST
INC R5
CJNE R5,#0AH,FIRT
MOV A,R6
SUBB A,#09H
MOV R6,A
JMP FIRST
FIRT:
JC FIRST
INC R4
CJNE R4,#0AH,FIRU
MOV A,R5
SUBB A,#09H
MOV R5,A
LJMP FIRST
FIRU:
JC FIRST
INC R3
MOV A,R4
SUBB A,#09H
MOV R4,A
LJMP FIRST
FIRA:
JC FIRST
INC R2
MOV A,R3
SUBB A,#09H
MOV R3,A
LJMP FIRST
FIRB:
JC FIRST
INC R1
MOV A,R2
SUBB A,#09H
MOV R2,A
LJMP FIRST
FIRC:
JC FIRST
INC R0
MOV A,R1
SUBB A,#09H
MOV R1,A
LJMP FIRST
OUTBA:
LJMP OUTB
OUT:
CLR C
MOV A,DIG2
SUBB A,#01H
MOV DIG2,A
JNC OUTB
CLR C
MOV A,DIG3
SUBB A,#01H
MOV DIG3,A
JNC OUTBA
MOV A,DIG1
ADD A,#0AH
MOV R7,A
RET
LINE1: DB ' Hi ALL !!!! '
LINE2: DB ' HAVE A GOOD DAY'
LINE3: DB ' Dist Measured '
LINE4: DB ' . cms '
NOPULSE: DB ' NO PULSE '
NOPULSEA: DB ' RECEIVED !!! '
ASCII: DB '0123456789ABCDEF'
END
