LCD version of the heart rate monitor. ~ CasinoDigitalTech

LCD version of the heart rate monitor.

A simple LCD version of the heart rate monitor is shown below. This is just a modification of the above circuit.LCD displays are very popular now a most of the embedded system designers prefer them over multiplexed seven segment LED displays. Using LCD displays you can display text, custom characters, graphics and a lot of other stuff and it is a great advantage over the LED counterparts. JHD162 is the LCD display used here. It is a 16X2 LCD display based on the HD44780 driver IC. Go through the following link for knowing more about JHD162 and its interfacing to the 8051 microcontroller. Interfacing LCD display to 8051. The circuit diagram of the LCD version of the heart rate monitor is shown below.

Data/command input pin DB0 to DB7 of the display is interfaced to Port0 of the microcontroller. Resistor network R17 is used for pulling up thePort0. Port0 needs external pull up for proper functioning. Preset resistor R1 is used for adjusting the contrast of the display. R2 limits the current through the back light LED. Other parts of the circuit are similar to the LED version.

Program.

RS EQU P2.7
RW EQU P2.6
EN EQU P2.5
ORG 000H
ACALL INIT
ACALL TEXT1
ACALL LINE2
ACALL TEXT3
MOV DPTR,#LUT
MOV P1,#00000000B
MOV P0,#00000000B
MAIN: MOV R6,#230D
SETB P3.5
MOV TMOD,#01100001B
MOV TL1,#00000000B
MOV TH1,#00000000B
SETB TR1
BACK: MOV TH0,#00000000B
MOV TL0,#00000000B
SETB TR0
HERE: JNB TF0,HERE
CLR TR0
CLR TF0
DJNZ R6,BACK
CLR TR1
CLR TF0
CLR TF1
MOV A,TL1
MOV B,#4D
MUL AB
ACALL SPLIT
ACALL INIT
ACALL TEXT1
ACALL LINE2
ACALL TEXT2
ACALL BPM

SJMP MAIN



INIT:

ACALL CMD
MOV A,#0FH
ACALL CMD
MOV A,#01H
ACALL CMD
MOV A,#06H
ACALL CMD
MOV A,#83H
ACALL CMD
MOV A,#3CH
ACALL CMD
RET

TEXT1:
MOV A,#48H
ACALL DISPLAY
MOV A,#65H
ACALL DISPLAY
MOV A,#61H
ACALL DISPLAY
MOV A,#72H
ACALL DISPLAY
MOV A,#74H
ACALL DISPLAY
MOV A,#20H
ACALL DISPLAY
MOV A,#52H
ACALL DISPLAY
MOV A,#61H
ACALL DISPLAY
MOV A,#74H
ACALL DISPLAY
MOV A,#65H
ACALL DISPLAY
RET

LINE2:

MOV A,#0C0H
ACALL CMD
RET
TEXT2:
MOV A,#62H
ACALL DISPLAY
MOV A,#70H
ACALL DISPLAY
MOV A,#6DH
ACALL DISPLAY
MOV A,#20H
ACALL DISPLAY
RET
TEXT3:
MOV A,#63H
ACALL DISPLAY
MOV A,#6FH
ACALL DISPLAY
MOV A,#75H
ACALL DISPLAY
MOV A,#6EH
ACALL DISPLAY
MOV A,#74H
ACALL DISPLAY
MOV A,#69H
ACALL DISPLAY
MOV A,#6EH
ACALL DISPLAY
MOV A,#67H
ACALL DISPLAY
MOV A,#2EH
ACALL DISPLAY
MOV A,#2EH
ACALL DISPLAY
MOV A,#2EH
ACALL DISPLAY
RET


BPM:
MOV A,R1
ACALL ASCII
ACALL DISPLAY
MOV A,R2
ACALL ASCII
ACALL DISPLAY
MOV A,R3
ACALL ASCII
ACALL DISPLAY
RET



CMD: MOV P0,A
CLR RS
CLR RW
SETB EN
CLR EN
ACALL DELAY
RET

DISPLAY:MOV P0,A
SETB RS
CLR RW
SETB EN
CLR EN
ACALL DELAY
RET

DELAY: CLR EN
CLR RS
SETB RW
MOV P0,#0FFh
SETB EN
MOV A,P0
JB ACC.7,DELAY

CLR EN
CLR RW
RET

DELAY1:MOV R5,#255D
HERE2:DJNZ R5,HERE2
RET

SPLIT: MOV B,#10D
DIV AB
MOV R3,B
MOV B,#10D
DIV AB
MOV R2,B
MOV R1,A
RET

ASCII: MOVC A,@A+DPTR
RET
LUT: DB 48D
DB 49D
DB 50D
DB 51D
DB 52D
DB 53D
DB 54D
DB 55D
DB 56D
DB 57D

END

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