PIC16F84A LCD Programming Help - Electronic Circuits Projects Diagrams Free

Frosty_47 · 13th August 2009, 01:03 AM

I successfully programmed DMC 16249 LCD in 8-bit parallel mode using PIC16F84A. Now my instructor wants me to program that same LCD in serial mode using 74LS164 shift register. I moded my code but all I get is a line and a half of blocks at the output. I already changed LCD, Shift Register, PIC16F84A and even tried it with PIC16F877 with no luck. My code has been reviewed by 3 people already with no one finding anything wrong with it. I don't know what I am doing wrong please help. My code below for reference:

Note: I use MPLAB v8.30, the code compiles with no errors. Also, I use Pickit 3 to program the PIC16F84A and PIC16F877.

Quote:

Code intentionally removed. Please see below for working code...

Frosty_47 · 13th August 2009, 05:31 AM

I was wondering if dead/faulty XTAL oscilator can cause this problem...
I mean what are the chance of XTAL failing ?

ericgibbs · 13th August 2009, 09:11 AM

Quote:

Originally Posted by Frosty_47

I was wondering if dead/faulty XTAL oscilator can cause this problem...
I mean what are the chance of XTAL failing ?

hi,
Ran in your program in the OS sim,OK, using a modified external S/R module. Note this ext module clocks on the low to high edge.

Look at these two images.
The S/R shows the 0x38 LCD setup code byte, have you wired the LCD so that D7 of the S/R is the LSB [D0] of the LCD.???

Also the clocking pulse in the program is going high to low,, the LS164 datasheet states a low to high clock pulse edge.???

Also are you resetting the LS164 at power up.??

Please post your circuit diagram.

EDIT:
The LCD setup sequence needs reworking.
Send at least 2 or 3, 0x38's remove all but one of the 0x06's and check the remainder.

Checked thru all the LCD init and data transfer, it checks OK in simulation.

blueroomelectronics · 13th August 2009, 03:11 PM

Use the PK3 debug mode on the 16F877. If the crystal isn't running it won't enter debug.

PS if you're using a solderless breadboard crystals may not work properly. Also don't forget 0.1uF decoupling caps on VDD &VSS they're not optional.

Frosty_47 · 13th August 2009, 03:13 PM

Thank you for taking time to help me.

I moded the code. However still get nothing at output. Oh and I don't see why the D7 of S/R be connected to LSB when I am shifting right... I tried that anyway with no luck

My moded code below for reference:

PHP Code:

  Code intentionally removed. Please see below for working code...

blueroomelectronics · 13th August 2009, 03:16 PM

Learn to use the debugger. Makes troubleshooting much easier.

ericgibbs · 13th August 2009, 03:46 PM

hi Frosty,

Unzip this zip into an avi and play on your Windows Media.

I have modified an Oshonsoft module to work as a 74LS164.

Frosty_47 · 13th August 2009, 08:04 PM

Quote:

Originally Posted by ericgibbs

hi Frosty,

Unzip this zip into an avi and play on your Windows Media.

I have modified an Oshonsoft module to work as a 74LS164.

WOW! Anymore and I gonna have to start paying you

Yeah, I changed the code to rotate LEFT, that way no need to reconnect the LCD. Still no luck... I get a blank display...

Frosty_47 · 13th August 2009, 11:19 PM

I GOT IT TO WORK! I found one eror in DATAWRT section:

Eror found: BCF PORTA,0 ;RS = 1 for command

Correct Code: BSF PORTA,0 ;RS = 1 for command

Also I had to add:

PHP Code:

  MOVLW    0x07                
CALL    COMNWRT
CALL    LDELAY

MOVLW    0x06                
CALL    COMNWRT
CALL    LDELAY

Without above addition, the characters would not be in their right specified positions...

Here is the Working Code:

PHP Code:

  list p=16F84A
#include <p16F84A.inc>

;***********************Setup constants***********************

BLA        equ        0x20
BLA2    equ        0x21
BLA3    equ        0x22
BLA4    equ        0x23
BLA5    equ        0x24

REG_1    equ        0x30
REG_2    equ        0x31
LOOP    equ        0x32
LOOP2    equ        0x33

;***********************Setup the PORT************************

org 0x00
goto main
org 0x10

main


bsf     STATUS,5            ;switch to Bank 1
MOVLW    0x00
MOVWF    TRISA                ;set all PORTA pins as outputs
MOVWF    TRISB                ;set all PORTB pins as outputs
bcf        STATUS,5            ;switch back to Bank0

Start

bcf        PORTA,2
CALL    LDELAY

MOVLW    0x38                ;initialize LCD 5x7 Matrix
CALL    COMNWRT
CALL    LDELAY

MOVLW    0x38                ;initialize LCD 5x7 Matrix
CALL    COMNWRT
CALL    LDELAY

MOVLW    0x07                
CALL    COMNWRT
CALL    LDELAY

MOVLW    0x06                
CALL    COMNWRT
CALL    LDELAY

MOVLW    0x0F                ;Display on, cursor blinking
CALL    COMNWRT
CALL    DELAY

MOVLW    0x85                ;cursor at line 1, position 5
CALL    COMNWRT
CALL    DELAY

MOVLW    0x41                ;Display letter 'A'
CALL    DATAWRT
CALL    DELAY

MOVLW    0x4E                ;Display letter 'N'
CALL    DATAWRT
CALL    DELAY

MOVLW    0x44                ;Display letter 'D'
CALL    DATAWRT
CALL    DELAY

MOVLW    0x52                ;Display letter 'R'
CALL    DATAWRT
CALL    DELAY

MOVLW    0x45                ;Display letter 'E'
CALL    DATAWRT
CALL    DELAY

MOVLW    0x49                ;Display letter 'I'
CALL    DATAWRT
CALL    DELAY

MOVLW    0xC5                ;cursor at line 2, position 4
CALL    COMNWRT
CALL    DELAY

MOVLW    0x4D                ;Display letter 'M'
CALL    DATAWRT
CALL    DELAY

MOVLW    0x4F                ;Display letter 'O'
CALL    DATAWRT
CALL    DELAY

MOVLW    0x52                ;Display letter 'R'
CALL    DATAWRT    
CALL    DELAY

MOVLW    0x4F                ;Display letter 'O'
CALL    DATAWRT
CALL    DELAY

MOVLW    0x5A                ;Display letter 'Z'
CALL    DATAWRT
CALL    DELAY

THERE    Goto    THERE        ;stay here (I mean there).

COMNWRT                        ;send command to LCD
        MOVWF    REG_1        ;coppy W to reg_1
        MOVLW    0x08        ;Load 8 to W
        MOVWF    LOOP        ;Load 8 to Loop
HERE    RLF        REG_1,1        ;rotate right
        BTFSS    STATUS,0    ;check carry
        bcf        PORTB,1        ;clear RB1 if carry = 0
        BTFSC    STATUS,0    ;check carry
        bsf        PORTB,1        ;set RB1 if carry = 1
        bcf        PORTB,0        ;clear clock
        bsf        PORTB,0        ;L-to-H clock pule
        bcf        PORTB,0        ;clear clock
        DECFSZ    LOOP,1        ;repeat 8 times
        GOTO    HERE    
        
        bcf        PORTA,0        ;RS = 0 for command
        bcf        PORTA,1        ;R/W = 0 for write
        bsf        PORTA,2        ;E = 1 for high pulse
        CALL    SDELAY        ;make a wide en pulse
        bcf        PORTA,2        ;E = 0 for H-to-L pulse
        RETURN



DATAWRT                        ;write data to LCD
                            ;copy W to LCD Data Pin
        MOVWF    REG_2        ;coppy W to reg_2
        MOVLW    0x08        ;Load 8 to W
        MOVWF    LOOP2        ;Load 8 to Loop2
HERE2    RLF        REG_2,1        ;rotate right
        BTFSS    STATUS,0    ;check carry
        bcf        PORTB,1        ;clear RB1 if carry = 0
        BTFSC    STATUS,0    ;check carry
        bsf        PORTB,1        ;set RB1 if carry = 1
        bcf        PORTB,0        ;clear clock
        bsf        PORTB,0        ;L-to-H clock pule
        bcf        PORTB,0        ;clear clock
        DECFSZ    LOOP2,1        ;repeat 8 times
        GOTO    HERE2    

        BSF        PORTA,0        ;RS = 1 for command
        BCF        PORTA,1        ;R/W = 0 for write
        BSF        PORTA,2        ;E = 1 for high pulse
        CALL    SDELAY        ;make a wide en pulse
        BCF        PORTA,2        ;E = 0 for H-to-L pulse
        RETURN


DELAY                        ;15.3mS LCD Write Delay
            MOVLW    0x44
            MOVWF    BLA
            MOVLW    0x19
            MOVWF    BLA2
            
BACK        DECFSZ    BLA,1
            GOTO    BACK
BACK2        DECFSZ    BLA2,1
            GOTO    BACK2
            RETURN


LDELAY                        ;4.5 second power-up delay
            MOVLW     0xFA
            MOVWF    BLA3
            MOVWF    BLA4
            MOVLW    0x02
            MOVWF    BLA5

BACK3        DECFSZ    BLA3,1
            GOTO    BACK3
BACK4        DECFSZ    BLA4,1
            GOTO    BACK4
BACK5        DECFSZ    BLA5,1
            GOTO    BACK5
            RETURN


SDELAY                        ;3uS En pulse delay
            NOP
            RETURN

            END

Thank you Ericgibbs for all your help and efforts!
I found your video to be very helpful in reminding me of shift register operation...

ericgibbs · 14th August 2009, 08:54 AM

hi,

Just a small point about your listing.

Code:

MOVLW "A";   0x41                ;Display letter 'A'
CALL    DATAWRT
CALL    DELAY

MOVLW   "N"; 0x4E                ;Display letter 'N'
CALL    DATAWRT
CALL    DELAY

MOVLW   "D"; 0x44                ;Display letter 'D'
CALL    DATAWRT
CALL    DELAY

MOVLW   "R" ;0x52                ;Display letter 'R'
CALL    DATAWRT
CALL    DELAY

MOVLW    "E";0x45                ;Display letter 'E'
CALL    DATAWRT
CALL    DELAY

You can use double quotes for the ASCII characters.

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13th August 2009, 05:31 AM	#2
Frosty_47	I was wondering if dead/faulty XTAL oscilator can cause this problem... I mean what are the chance of XTAL failing ? __________________ "The people who cast the votes don't decide an election, the people who count the votes do." -Joseph Stalin

13th August 2009, 03:11 PM	#4
blueroomelectronics	Use the PK3 debug mode on the 16F877. If the crystal isn't running it won't enter debug. PS if you're using a solderless breadboard crystals may not work properly. Also don't forget 0.1uF decoupling caps on VDD &VSS they're not optional. __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com/

13th August 2009, 03:13 PM	#5
Frosty_47	Thank you for taking time to help me. I moded the code. However still get nothing at output. Oh and I don't see why the D7 of S/R be connected to LSB when I am shifting right... I tried that anyway with no luck My moded code below for reference: PHP Code: `Code intentionally removed. Please see below for working code...` __________________ "The people who cast the votes don't decide an election, the people who count the votes do." -Joseph Stalin Last edited by Frosty_47; 13th August 2009 at 11:15 PM.

13th August 2009, 03:16 PM	#6
blueroomelectronics	Learn to use the debugger. Makes troubleshooting much easier. __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com/

13th August 2009, 11:19 PM	#9
Frosty_47	Finaly ! I GOT IT TO WORK! I found one eror in DATAWRT section: Eror found: BCF PORTA,0 ;RS = 1 for command Correct Code: BSF PORTA,0 ;RS = 1 for command Also I had to add: PHP Code: `MOVLW 0x07 CALL COMNWRT CALL LDELAY MOVLW 0x06 CALL COMNWRT CALL LDELAY` Without above addition, the characters would not be in their right specified positions... Here is the Working Code: PHP Code: list p=16F84A #include <p16F84A.inc> ;*********************Setup constants******************* BLA equ 0x20 BLA2 equ 0x21 BLA3 equ 0x22 BLA4 equ 0x23 BLA5 equ 0x24 REG_1 equ 0x30 REG_2 equ 0x31 LOOP equ 0x32 LOOP2 equ 0x33 ;*******************Setup the PORT********************** org 0x00 goto main org 0x10 main bsf STATUS,5 ;switch to Bank 1 MOVLW 0x00 MOVWF TRISA ;set all PORTA pins as outputs MOVWF TRISB ;set all PORTB pins as outputs bcf STATUS,5 ;switch back to Bank0 Start bcf PORTA,2 CALL LDELAY MOVLW 0x38 ;initialize LCD 5x7 Matrix CALL COMNWRT CALL LDELAY MOVLW 0x38 ;initialize LCD 5x7 Matrix CALL COMNWRT CALL LDELAY MOVLW 0x07 CALL COMNWRT CALL LDELAY MOVLW 0x06 CALL COMNWRT CALL LDELAY MOVLW 0x0F ;Display on, cursor blinking CALL COMNWRT CALL DELAY MOVLW 0x85 ;cursor at line 1, position 5 CALL COMNWRT CALL DELAY MOVLW 0x41 ;Display letter 'A' CALL DATAWRT CALL DELAY MOVLW 0x4E ;Display letter 'N' CALL DATAWRT CALL DELAY MOVLW 0x44 ;Display letter 'D' CALL DATAWRT CALL DELAY MOVLW 0x52 ;Display letter 'R' CALL DATAWRT CALL DELAY MOVLW 0x45 ;Display letter 'E' CALL DATAWRT CALL DELAY MOVLW 0x49 ;Display letter 'I' CALL DATAWRT CALL DELAY MOVLW 0xC5 ;cursor at line 2, position 4 CALL COMNWRT CALL DELAY MOVLW 0x4D ;Display letter 'M' CALL DATAWRT CALL DELAY MOVLW 0x4F ;Display letter 'O' CALL DATAWRT CALL DELAY MOVLW 0x52 ;Display letter 'R' CALL DATAWRT CALL DELAY MOVLW 0x4F ;Display letter 'O' CALL DATAWRT CALL DELAY MOVLW 0x5A ;Display letter 'Z' CALL DATAWRT CALL DELAY THERE Goto THERE ;stay here (I mean there). COMNWRT ;send command to LCD MOVWF REG_1 ;coppy W to reg_1 MOVLW 0x08 ;Load 8 to W MOVWF LOOP ;Load 8 to Loop HERE RLF REG_1,1 ;rotate right BTFSS STATUS,0 ;check carry bcf PORTB,1 ;clear RB1 if carry = 0 BTFSC STATUS,0 ;check carry bsf PORTB,1 ;set RB1 if carry = 1 bcf PORTB,0 ;clear clock bsf PORTB,0 ;L-to-H clock pule bcf PORTB,0 ;clear clock DECFSZ LOOP,1 ;repeat 8 times GOTO HERE bcf PORTA,0 ;RS = 0 for command bcf PORTA,1 ;R/W = 0 for write bsf PORTA,2 ;E = 1 for high pulse CALL SDELAY ;make a wide en pulse bcf PORTA,2 ;E = 0 for H-to-L pulse RETURN DATAWRT ;write data to LCD ;copy W to LCD Data Pin MOVWF REG_2 ;coppy W to reg_2 MOVLW 0x08 ;Load 8 to W MOVWF LOOP2 ;Load 8 to Loop2 HERE2 RLF REG_2,1 ;rotate right BTFSS STATUS,0 ;check carry bcf PORTB,1 ;clear RB1 if carry = 0 BTFSC STATUS,0 ;check carry bsf PORTB,1 ;set RB1 if carry = 1 bcf PORTB,0 ;clear clock bsf PORTB,0 ;L-to-H clock pule bcf PORTB,0 ;clear clock DECFSZ LOOP2,1 ;repeat 8 times GOTO HERE2 BSF PORTA,0 ;RS = 1 for command BCF PORTA,1 ;R/W = 0 for write BSF PORTA,2 ;E = 1 for high pulse CALL SDELAY ;make a wide en pulse BCF PORTA,2 ;E = 0 for H-to-L pulse RETURN DELAY ;15.3mS LCD Write Delay MOVLW 0x44 MOVWF BLA MOVLW 0x19 MOVWF BLA2 BACK DECFSZ BLA,1 GOTO BACK BACK2 DECFSZ BLA2,1 GOTO BACK2 RETURN LDELAY ;4.5 second power-up delay MOVLW 0xFA MOVWF BLA3 MOVWF BLA4 MOVLW 0x02 MOVWF BLA5 BACK3 DECFSZ BLA3,1 GOTO BACK3 BACK4 DECFSZ BLA4,1 GOTO BACK4 BACK5 DECFSZ BLA5,1 GOTO BACK5 RETURN SDELAY ;3uS En pulse delay NOP RETURN END Thank you Ericgibbs for all your help and efforts! I found your video to be very helpful in reminding me of shift register operation... __________________ "The people who cast the votes don't decide an election, the people who count the votes do." -Joseph Stalin Last edited by Frosty_47; 13th August 2009 at 11:29 PM.

14th August 2009, 08:54 AM	#10
ericgibbs	hi, Just a small point about your listing. Code: MOVLW "A"; 0x41 ;Display letter 'A' CALL DATAWRT CALL DELAY MOVLW "N"; 0x4E ;Display letter 'N' CALL DATAWRT CALL DELAY MOVLW "D"; 0x44 ;Display letter 'D' CALL DATAWRT CALL DELAY MOVLW "R" ;0x52 ;Display letter 'R' CALL DATAWRT CALL DELAY MOVLW "E";0x45 ;Display letter 'E' CALL DATAWRT CALL DELAY You can use double quotes for the ASCII characters. __________________ Eric " Good enough is Perfect " I will NOT answer PM's requesting technical help, please use the Forum PIC tutorials: Nigel's www.winpicprog.co.uk/ Bill's: www.blueroomelectronics.com/