I have an Optrex LCD (DMC-20481NY-LY-AGE) that is 4x20 characters and driven by a Microchip PIC16F877 running at 20MHz. I know I got this exact same physical LCD to work before but for the life of me I can't recall what trick I used to do so. Attached at the end is my software. I get power to the LCD, but all I see is lines 1 and 3 as all dark and lines 2 and 4 as all clear. Hunting around newsgroups leads me to think my initialization routines aren't working (gee, ya think?!?!) but as near as I can tell I have met or exceeded all of the timing requirements for data transfer. PLEASE HELP!!!!! If it matters, I am using a dedicated 5V DC supply to drive both the PIC and the LCD. The PIC is connected to the LCD through 330 Ohm resistors, with 10KOhm pulldown resistors to ground on ALL of the lines on the PIC side. This was because I was seeing a lot of glitches on powerup due to ports being inputs. Each line also has a .01uF cap to ground and there is a bypass capacitor on the 5V line to ground next to the PIC. The BusyFlag is also connected directly from the LCD to the PIC on PORTB, 6. Thanks for any insight! -Will ; LCD Control Software ; ; Software uses a 20MHz crystal ; for timing. ; ;****************************************************************** Stall MACRO LOCAL Stall_Jump goto Stall_Jump Stall_Jump ENDM ;****************************************************************** Wait_For_Busy_Flag MACRO btfsc BUSY_FLAG goto $-1 ENDM ;****************************************************************** Wait_15ms MACRO LOCAL OuterLoop LOCAL InnerLoop movlw .59 movwf OUTER_COUNTER OuterLoop movlw .255 movwf INNER_COUNTER InnerLoop Stall decfsz INNER_COUNTER, F goto InnerLoop decfsz OUTER_COUNTER, F goto OuterLoop ENDM ;****************************************************************** Wait_4.1ms MACRO LOCAL OuterLoop LOCAL InnerLoop movlw .17 movwf OUTER_COUNTER OuterLoop movlw .255 movwf INNER_COUNTER InnerLoop Stall decfsz INNER_COUNTER, F goto InnerLoop decfsz OUTER_COUNTER, F goto OuterLoop ENDM ;****************************************************************** Wait_100us MACRO LOCAL InnerLoop movlw .100 movwf INNER_COUNTER InnerLoop Stall decfsz INNER_COUNTER, F goto InnerLoop ENDM ;****************************************************************** list p=16F877 ; Include file, change directory if needed include "p16f877.inc" #define ENABLE PORTE, 2 #define RS PORTE, 1 #define RW PORTE, 0 #define DATA_PORT PORTD #define BUSY_FLAG PORTB, 6 OUTER_COUNTER equ 0x20 INNER_COUNTER equ 0x21 W_TEMP equ 0x70 STATUS_TEMP equ 0x71 PCLATH_TEMP equ 0x72 ;//Reset Vector Org 0x00 clrf PCLATH ; ensure page bits are cleared goto Initialize ;//Interrupt Vector ORG 0x04 MOVWF W_TEMP ;Copy W to TEMP register SWAPF STATUS,W ;Swap status to be saved into W CLRF STATUS ;bank 0, regardless of current bank, Clears IRP,RP1,RP0 MOVWF STATUS_TEMP ;Save status to bank zero STATUS_TEMP register MOVF PCLATH, W ;Only required if using pages 1, 2 and/or 3 MOVWF PCLATH_TEMP ;Save PCLATH into W CLRF PCLATH ;Page zero, regardless of current page ;Fill this in if you want interrupt vectoring banksel PCLATH_TEMP MOVF PCLATH_TEMP, W ;Restore PCLATH MOVWF PCLATH ;Move W into PCLATH SWAPF STATUS_TEMP,W ;Swap STATUS_TEMP register into W ;(sets bank to original state) MOVWF STATUS ;Move W into STATUS register SWAPF W_TEMP,F ;Swap W_TEMP SWAPF W_TEMP,W ;Swap W_TEMP into W retfie ; return from interrupt ;//Initialization Initialize clrf INTCON clrf INTCON CGIE bcf INTCON, GIE btfsc INTCON, GIE goto CGIE ; //Declare port/pin definitions banksel TRISA movlw B'00000111' movwf ADCON1 ; Port A is all digital movlw B'00000000' movwf TRISA ; Port A is OOOOOOOO movlw B'01000000' movwf TRISB ; Port B is OIOOOOOO movlw B'10000001' movwf TRISC ; Port C is IOOOOOOI movlw B'00000000' movwf TRISD ; Port D is OOOOOOOO bcf TRISE, PSPMODE ; Turn off the parallel port bcf TRISE, 0 ; Port E is -----OOO bcf TRISE, 1 bcf TRISE, 2 bsf OPTION_REG, 7 ;Turn off port B pullups banksel OUTER_COUNTER bsf PORTB, 7 Wait_15ms Wait_15ms bcf PORTB, 7 bcf RS bcf RW movlw b'00111000' call StrobeData Wait_4.1ms Wait_4.1ms bcf RS bcf RW movlw b'00111000' call StrobeData Wait_4.1ms Wait_4.1ms bcf RS bcf RW movlw b'00111000' call StrobeData Wait_4.1ms Wait_4.1ms call DisplayOFF_CursorOFF_BlinkOFF Wait_15ms Wait_4.1ms call DisplayON_CursorON_BlinkON Wait_15ms Wait_4.1ms call EntryModeSet Wait_100us call ClearDisplay Wait_15ms Wait_4.1ms movlw b'01001000' ;H call SendChar movlw b'01100101' ;e call SendChar movlw b'01101100' ;l call SendChar movlw b'01101100' ;l call SendChar movlw b'01101111' ;o call SendChar movlw b'01010111' ;W call SendChar movlw b'01101111' ;o call SendChar movlw b'01110010' ;r call SendChar movlw b'01101100' ;l call SendChar movlw b'01100100' ;d call SendChar Eternal bcf PORTB, 0 nop bsf PORTB, 0 goto Eternal ;----------- StrobeData nop bsf ENABLE nop movwf DATA_PORT nop bcf ENABLE return ;----------- EntryModeSet btfsc BUSY_FLAG goto EntryModeSet bcf RS bcf RW movlw b'00000110' call StrobeData return ;----------- SendChar btfsc BUSY_FLAG goto SendChar bsf RS bcf RW call StrobeData return ;----------- ClearDisplay btfsc BUSY_FLAG goto ClearDisplay bcf RS bcf RW movlw 0x01 call StrobeData return ;----------- HomeCursor btfsc BUSY_FLAG goto HomeCursor bcf RS bcf RW movlw 0x02 call StrobeData return ;----------- DisplayOFF_CursorOFF_BlinkOFF btfsc BUSY_FLAG goto DisplayOFF_CursorOFF_BlinkOFF bcf RS bcf RW movlw b'00001000' call StrobeData return ;----------- DisplayOFF_CursorOFF_BlinkON btfsc BUSY_FLAG goto DisplayOFF_CursorOFF_BlinkON bcf RS bcf RW movlw b'00001001' call StrobeData return ;----------- DisplayOFF_CursorON_BlinkOFF btfsc BUSY_FLAG goto DisplayOFF_CursorON_BlinkOFF bcf RS bcf RW movlw b'00001010' call StrobeData return ;----------- DisplayOFF_CursorON_BlinkON btfsc BUSY_FLAG goto DisplayOFF_CursorON_BlinkON bcf RS bcf RW movlw b'00001011' call StrobeData return ;----------- DisplayON_CursorOFF_BlinkOFF btfsc BUSY_FLAG goto DisplayON_CursorOFF_BlinkOFF bcf RS bcf RW movlw b'00001100' call StrobeData return ;----------- DisplayON_CursorOFF_BlinkON btfsc BUSY_FLAG goto DisplayON_CursorOFF_BlinkON bcf RS bcf RW movlw b'00001101' call StrobeData return ;----------- DisplayON_CursorON_BlinkOFF btfsc BUSY_FLAG goto DisplayON_CursorON_BlinkOFF bcf RS bcf RW movlw b'00001110' call StrobeData return ;----------- DisplayON_CursorON_BlinkON btfsc BUSY_FLAG goto DisplayON_CursorON_BlinkON bcf RS bcf RW movlw b'00001111' call StrobeData return ;----------- END
Help getting an LCD to work
Started by ●February 3, 2004
Reply by ●February 3, 20042004-02-03
Hi, the 2 dark lines means that the module has not been initialised. Remove all the components from the connections to the module, just connect directly.
Reply by ●February 3, 20042004-02-03
Hi again, i just noited that your "strobe data" is too fast, check the data sheet for timming, also your should put the data on the port before the enable pulse.
Reply by ●February 3, 20042004-02-03
Will wrote:> I have an Optrex LCD (DMC-20481NY-LY-AGE) that is 4x20 characters and > driven by a Microchip PIC16F877 running at 20MHz. I know I got this > exact same physical LCD to work before but for the life of me I can't > recall what trick I used to do so. Attached at the end is my > software. I get power to the LCD, but all I see is lines 1 and 3 as > all dark and lines 2 and 4 as all clear. Hunting around newsgroups > leads me to think my initialization routines aren't working (gee, ya > think?!?!) but as near as I can tell I have met or exceeded all of the > timing requirements for data transfer. PLEASE HELP!!!!! If it > matters, I am using a dedicated 5V DC supply to drive both the PIC and > the LCD. The PIC is connected to the LCD through 330 Ohm resistors, > with 10KOhm pulldown resistors to ground on ALL of the lines on the > PIC side. This was because I was seeing a lot of glitches on powerup > due to ports being inputs. Each line also has a .01uF cap to ground > and there is a bypass capacitor on the 5V line to ground next to the > PIC. The BusyFlag is also connected directly from the LCD to the PIC > on PORTB, 6. Thanks for any insight![...] 10nF on each signal line is quite a lot! Why do you need such a big capacitive load on the data wires? Have you checked the timing on a scope, or are you just counting clock cycles in your program? -- Cheers Stefan
Reply by ●February 3, 20042004-02-03
Make sure you have the proper delays in the Init routines. I've used the same display and had problems with short delays in the Init routines. Cheers "Will" <larkmore@aol.com> wrote in message news:5faf6114.0402031434.38db8ce2@posting.google.com...> I have an Optrex LCD (DMC-20481NY-LY-AGE) that is 4x20 characters and > driven by a Microchip PIC16F877 running at 20MHz. I know I got this > exact same physical LCD to work before but for the life of me I can't > recall what trick I used to do so. Attached at the end is my > software. I get power to the LCD, but all I see is lines 1 and 3 as > all dark and lines 2 and 4 as all clear. Hunting around newsgroups > leads me to think my initialization routines aren't working (gee, ya > think?!?!) but as near as I can tell I have met or exceeded all of the > timing requirements for data transfer. PLEASE HELP!!!!! If it > matters, I am using a dedicated 5V DC supply to drive both the PIC and > the LCD. The PIC is connected to the LCD through 330 Ohm resistors, > with 10KOhm pulldown resistors to ground on ALL of the lines on the > PIC side. This was because I was seeing a lot of glitches on powerup > due to ports being inputs. Each line also has a .01uF cap to ground > and there is a bypass capacitor on the 5V line to ground next to the > PIC. The BusyFlag is also connected directly from the LCD to the PIC > on PORTB, 6. Thanks for any insight! > -Will > > ; LCD Control Software > ; > ; Software uses a 20MHz crystal > ; for timing. > ; > > ;****************************************************************** > Stall MACRO > LOCAL Stall_Jump > goto Stall_Jump > Stall_Jump > ENDM > ;****************************************************************** > Wait_For_Busy_Flag MACRO > btfsc BUSY_FLAG > goto $-1 > ENDM > ;****************************************************************** > Wait_15ms MACRO > LOCAL OuterLoop > LOCAL InnerLoop > > movlw .59 > movwf OUTER_COUNTER > OuterLoop > movlw .255 > movwf INNER_COUNTER > InnerLoop > Stall > decfsz INNER_COUNTER, F > goto InnerLoop > decfsz OUTER_COUNTER, F > goto OuterLoop > ENDM > ;****************************************************************** > Wait_4.1ms MACRO > LOCAL OuterLoop > LOCAL InnerLoop > > movlw .17 > movwf OUTER_COUNTER > OuterLoop > movlw .255 > movwf INNER_COUNTER > InnerLoop > Stall > decfsz INNER_COUNTER, F > goto InnerLoop > decfsz OUTER_COUNTER, F > goto OuterLoop > ENDM > ;****************************************************************** > Wait_100us MACRO > LOCAL InnerLoop > > movlw .100 > movwf INNER_COUNTER > InnerLoop > Stall > decfsz INNER_COUNTER, F > goto InnerLoop > ENDM > ;****************************************************************** > > list p=16F877 > > ; Include file, change directory if needed > include "p16f877.inc" > > #define ENABLE PORTE, 2 > #define RS PORTE, 1 > #define RW PORTE, 0 > > #define DATA_PORT PORTD > #define BUSY_FLAG PORTB, 6 > > OUTER_COUNTER equ 0x20 > INNER_COUNTER equ 0x21 > > > W_TEMP equ 0x70 > STATUS_TEMP equ 0x71 > PCLATH_TEMP equ 0x72 > > > ;//Reset Vector > Org 0x00 > clrf PCLATH ; ensure page bits are cleared > goto Initialize > > ;//Interrupt Vector > ORG 0x04 > MOVWF W_TEMP ;Copy W to TEMP register > SWAPF STATUS,W ;Swap status to be saved into W > CLRF STATUS ;bank 0, regardless of current bank, Clears > IRP,RP1,RP0 > MOVWF STATUS_TEMP ;Save status to bank zero STATUS_TEMP > register > MOVF PCLATH, W ;Only required if using pages 1, 2 and/or 3 > MOVWF PCLATH_TEMP ;Save PCLATH into W > CLRF PCLATH ;Page zero, regardless of current page > > ;Fill this in if you want interrupt vectoring > > banksel PCLATH_TEMP > MOVF PCLATH_TEMP, W ;Restore PCLATH > MOVWF PCLATH ;Move W into PCLATH > SWAPF STATUS_TEMP,W ;Swap STATUS_TEMP register into W > ;(sets bank to original state) > MOVWF STATUS ;Move W into STATUS register > SWAPF W_TEMP,F ;Swap W_TEMP > SWAPF W_TEMP,W ;Swap W_TEMP into W > retfie ; return from interrupt > > ;//Initialization > Initialize > clrf INTCON > clrf INTCON > CGIE > bcf INTCON, GIE > btfsc INTCON, GIE > goto CGIE > > ; //Declare port/pin definitions > banksel TRISA > movlw B'00000111' > movwf ADCON1 ; Port A is all digital > movlw B'00000000' > movwf TRISA ; Port A is OOOOOOOO > movlw B'01000000' > movwf TRISB ; Port B is OIOOOOOO > movlw B'10000001' > movwf TRISC ; Port C is IOOOOOOI > movlw B'00000000' > movwf TRISD ; Port D is OOOOOOOO > bcf TRISE, PSPMODE ; Turn off the parallel port > bcf TRISE, 0 ; Port E is -----OOO > bcf TRISE, 1 > bcf TRISE, 2 > > bsf OPTION_REG, 7 ;Turn off port B pullups > > banksel OUTER_COUNTER > bsf PORTB, 7 > > Wait_15ms > Wait_15ms > > bcf PORTB, 7 > > bcf RS > bcf RW > movlw b'00111000' > call StrobeData > > Wait_4.1ms > Wait_4.1ms > > bcf RS > bcf RW > movlw b'00111000' > call StrobeData > > Wait_4.1ms > Wait_4.1ms > > bcf RS > bcf RW > movlw b'00111000' > call StrobeData > > Wait_4.1ms > Wait_4.1ms > > call DisplayOFF_CursorOFF_BlinkOFF > Wait_15ms > Wait_4.1ms > > call DisplayON_CursorON_BlinkON > Wait_15ms > Wait_4.1ms > > call EntryModeSet > Wait_100us > > call ClearDisplay > Wait_15ms > Wait_4.1ms > > movlw b'01001000' ;H > call SendChar > movlw b'01100101' ;e > call SendChar > movlw b'01101100' ;l > call SendChar > movlw b'01101100' ;l > call SendChar > movlw b'01101111' ;o > call SendChar > movlw b'01010111' ;W > call SendChar > movlw b'01101111' ;o > call SendChar > movlw b'01110010' ;r > call SendChar > movlw b'01101100' ;l > call SendChar > movlw b'01100100' ;d > call SendChar > > Eternal > bcf PORTB, 0 > nop > bsf PORTB, 0 > goto Eternal > > ;----------- > StrobeData > nop > bsf ENABLE > nop > movwf DATA_PORT > nop > bcf ENABLE > return > ;----------- > EntryModeSet > btfsc BUSY_FLAG > goto EntryModeSet > bcf RS > bcf RW > movlw b'00000110' > call StrobeData > return > ;----------- > SendChar > btfsc BUSY_FLAG > goto SendChar > bsf RS > bcf RW > call StrobeData > return > ;----------- > ClearDisplay > btfsc BUSY_FLAG > goto ClearDisplay > bcf RS > bcf RW > movlw 0x01 > call StrobeData > return > ;----------- > HomeCursor > btfsc BUSY_FLAG > goto HomeCursor > bcf RS > bcf RW > movlw 0x02 > call StrobeData > return > ;----------- > DisplayOFF_CursorOFF_BlinkOFF > btfsc BUSY_FLAG > goto DisplayOFF_CursorOFF_BlinkOFF > bcf RS > bcf RW > movlw b'00001000' > call StrobeData > return > ;----------- > DisplayOFF_CursorOFF_BlinkON > btfsc BUSY_FLAG > goto DisplayOFF_CursorOFF_BlinkON > bcf RS > bcf RW > movlw b'00001001' > call StrobeData > return > ;----------- > DisplayOFF_CursorON_BlinkOFF > btfsc BUSY_FLAG > goto DisplayOFF_CursorON_BlinkOFF > bcf RS > bcf RW > movlw b'00001010' > call StrobeData > return > ;----------- > DisplayOFF_CursorON_BlinkON > btfsc BUSY_FLAG > goto DisplayOFF_CursorON_BlinkON > bcf RS > bcf RW > movlw b'00001011' > call StrobeData > return > ;----------- > DisplayON_CursorOFF_BlinkOFF > btfsc BUSY_FLAG > goto DisplayON_CursorOFF_BlinkOFF > bcf RS > bcf RW > movlw b'00001100' > call StrobeData > return > ;----------- > DisplayON_CursorOFF_BlinkON > btfsc BUSY_FLAG > goto DisplayON_CursorOFF_BlinkON > bcf RS > bcf RW > movlw b'00001101' > call StrobeData > return > ;----------- > DisplayON_CursorON_BlinkOFF > btfsc BUSY_FLAG > goto DisplayON_CursorON_BlinkOFF > bcf RS > bcf RW > movlw b'00001110' > call StrobeData > return > ;----------- > DisplayON_CursorON_BlinkON > btfsc BUSY_FLAG > goto DisplayON_CursorON_BlinkON > bcf RS > bcf RW > movlw b'00001111' > call StrobeData > return > ;----------- > END
Reply by ●February 4, 20042004-02-04
I can only tell you from my experience which things made my life difficult with LCD. 1. Contrast voltage had to be negative. I belive it isn't the case in your case, you only have to connect 10k potentiometer for contrast. 2. Inpropper initialization routine. Wrong sequence of initialization commands. If order off commands is not right it can cause a lot of headaches. 3. Using BUSY flag? When using BUSY flag you have to watch carefuly during the initialization routine when the busy flag can be checked. In your case my guess you would be you have incorrect initialization routine maybe timings are ok but the order of commands isn't. I had done initialization as written in one datasheet of my 2x16 LCD, and it worked badly sometimes it would initialize the LCD, and sometimes wouldn't I found another sequence for initializing on the Internet and it worked great since then. Mickey
Reply by ●February 4, 20042004-02-04
"Will" <larkmore@aol.com> wrote in message news:5faf6114.0402031434.38db8ce2@posting.google.com...> I have an Optrex LCD (DMC-20481NY-LY-AGE) that is 4x20 characters and > driven by a Microchip PIC16F877 running at 20MHz. I know I got this > exact same physical LCD to work before but for the life of me I can't > recall what trick I used to do so. Attached at the end is my > software. I get power to the LCD, but all I see is lines 1 and 3 as > all dark and lines 2 and 4 as all clear. Hunting around newsgroups > leads me to think my initialization routines aren't working (gee, ya > think?!?!) but as near as I can tell I have met or exceeded all of the > timing requirements for data transfer. PLEASE HELP!!!!! If it > matters, I am using a dedicated 5V DC supply to drive both the PIC and > the LCD. The PIC is connected to the LCD through 330 Ohm resistors, > with 10KOhm pulldown resistors to ground on ALL of the lines on the > PIC side. This was because I was seeing a lot of glitches on powerup > due to ports being inputs. Each line also has a .01uF cap to ground > and there is a bypass capacitor on the 5V line to ground next to the > PIC. The BusyFlag is also connected directly from the LCD to the PIC > on PORTB, 6. Thanks for any insight! > -WillYour strobedata routine is too fast. Many LCD displays have a cycle time of 500ns to 1000ns, where the E has to be kept high for 300 to 500ns or longer. Apart from that, your filtering of the datalines kills your signals. 0.01uF and 330 Ohm has a time constant of 3.3us. Your signals in the order of 1us cycle times will NEVER pass this filter. Remove the caps and resistors and you'll be fine. Meindert
Reply by ●February 4, 20042004-02-04
Have a look at this very usfull sofware pic simulator including lcd http://www.oshonsoft.com/pic.html regards bob "Will" <larkmore@aol.com> wrote in message news:5faf6114.0402031434.38db8ce2@posting.google.com...> I have an Optrex LCD (DMC-20481NY-LY-AGE) that is 4x20 characters and > driven by a Microchip PIC16F877 running at 20MHz. I know I got this > exact same physical LCD to work before but for the life of me I can't > recall what trick I used to do so. Attached at the end is my > software. I get power to the LCD, but all I see is lines 1 and 3 as > all dark and lines 2 and 4 as all clear. Hunting around newsgroups > leads me to think my initialization routines aren't working (gee, ya > think?!?!) but as near as I can tell I have met or exceeded all of the > timing requirements for data transfer. PLEASE HELP!!!!! If it > matters, I am using a dedicated 5V DC supply to drive both the PIC and > the LCD. The PIC is connected to the LCD through 330 Ohm resistors, > with 10KOhm pulldown resistors to ground on ALL of the lines on the > PIC side. This was because I was seeing a lot of glitches on powerup > due to ports being inputs. Each line also has a .01uF cap to ground > and there is a bypass capacitor on the 5V line to ground next to the > PIC. The BusyFlag is also connected directly from the LCD to the PIC > on PORTB, 6. Thanks for any insight! > -Will > > ; LCD Control Software > ; > ; Software uses a 20MHz crystal > ; for timing. > ; > > ;****************************************************************** > Stall MACRO > LOCAL Stall_Jump > goto Stall_Jump > Stall_Jump > ENDM > ;****************************************************************** > Wait_For_Busy_Flag MACRO > btfsc BUSY_FLAG > goto $-1 > ENDM > ;****************************************************************** > Wait_15ms MACRO > LOCAL OuterLoop > LOCAL InnerLoop > > movlw .59 > movwf OUTER_COUNTER > OuterLoop > movlw .255 > movwf INNER_COUNTER > InnerLoop > Stall > decfsz INNER_COUNTER, F > goto InnerLoop > decfsz OUTER_COUNTER, F > goto OuterLoop > ENDM > ;****************************************************************** > Wait_4.1ms MACRO > LOCAL OuterLoop > LOCAL InnerLoop > > movlw .17 > movwf OUTER_COUNTER > OuterLoop > movlw .255 > movwf INNER_COUNTER > InnerLoop > Stall > decfsz INNER_COUNTER, F > goto InnerLoop > decfsz OUTER_COUNTER, F > goto OuterLoop > ENDM > ;****************************************************************** > Wait_100us MACRO > LOCAL InnerLoop > > movlw .100 > movwf INNER_COUNTER > InnerLoop > Stall > decfsz INNER_COUNTER, F > goto InnerLoop > ENDM > ;****************************************************************** > > list p=16F877 > > ; Include file, change directory if needed > include "p16f877.inc" > > #define ENABLE PORTE, 2 > #define RS PORTE, 1 > #define RW PORTE, 0 > > #define DATA_PORT PORTD > #define BUSY_FLAG PORTB, 6 > > OUTER_COUNTER equ 0x20 > INNER_COUNTER equ 0x21 > > > W_TEMP equ 0x70 > STATUS_TEMP equ 0x71 > PCLATH_TEMP equ 0x72 > > > ;//Reset Vector > Org 0x00 > clrf PCLATH ; ensure page bits are cleared > goto Initialize > > ;//Interrupt Vector > ORG 0x04 > MOVWF W_TEMP ;Copy W to TEMP register > SWAPF STATUS,W ;Swap status to be saved into W > CLRF STATUS ;bank 0, regardless of current bank, Clears > IRP,RP1,RP0 > MOVWF STATUS_TEMP ;Save status to bank zero STATUS_TEMP > register > MOVF PCLATH, W ;Only required if using pages 1, 2 and/or 3 > MOVWF PCLATH_TEMP ;Save PCLATH into W > CLRF PCLATH ;Page zero, regardless of current page > > ;Fill this in if you want interrupt vectoring > > banksel PCLATH_TEMP > MOVF PCLATH_TEMP, W ;Restore PCLATH > MOVWF PCLATH ;Move W into PCLATH > SWAPF STATUS_TEMP,W ;Swap STATUS_TEMP register into W > ;(sets bank to original state) > MOVWF STATUS ;Move W into STATUS register > SWAPF W_TEMP,F ;Swap W_TEMP > SWAPF W_TEMP,W ;Swap W_TEMP into W > retfie ; return from interrupt > > ;//Initialization > Initialize > clrf INTCON > clrf INTCON > CGIE > bcf INTCON, GIE > btfsc INTCON, GIE > goto CGIE > > ; //Declare port/pin definitions > banksel TRISA > movlw B'00000111' > movwf ADCON1 ; Port A is all digital > movlw B'00000000' > movwf TRISA ; Port A is OOOOOOOO > movlw B'01000000' > movwf TRISB ; Port B is OIOOOOOO > movlw B'10000001' > movwf TRISC ; Port C is IOOOOOOI > movlw B'00000000' > movwf TRISD ; Port D is OOOOOOOO > bcf TRISE, PSPMODE ; Turn off the parallel port > bcf TRISE, 0 ; Port E is -----OOO > bcf TRISE, 1 > bcf TRISE, 2 > > bsf OPTION_REG, 7 ;Turn off port B pullups > > banksel OUTER_COUNTER > bsf PORTB, 7 > > Wait_15ms > Wait_15ms > > bcf PORTB, 7 > > bcf RS > bcf RW > movlw b'00111000' > call StrobeData > > Wait_4.1ms > Wait_4.1ms > > bcf RS > bcf RW > movlw b'00111000' > call StrobeData > > Wait_4.1ms > Wait_4.1ms > > bcf RS > bcf RW > movlw b'00111000' > call StrobeData > > Wait_4.1ms > Wait_4.1ms > > call DisplayOFF_CursorOFF_BlinkOFF > Wait_15ms > Wait_4.1ms > > call DisplayON_CursorON_BlinkON > Wait_15ms > Wait_4.1ms > > call EntryModeSet > Wait_100us > > call ClearDisplay > Wait_15ms > Wait_4.1ms > > movlw b'01001000' ;H > call SendChar > movlw b'01100101' ;e > call SendChar > movlw b'01101100' ;l > call SendChar > movlw b'01101100' ;l > call SendChar > movlw b'01101111' ;o > call SendChar > movlw b'01010111' ;W > call SendChar > movlw b'01101111' ;o > call SendChar > movlw b'01110010' ;r > call SendChar > movlw b'01101100' ;l > call SendChar > movlw b'01100100' ;d > call SendChar > > Eternal > bcf PORTB, 0 > nop > bsf PORTB, 0 > goto Eternal > > ;----------- > StrobeData > nop > bsf ENABLE > nop > movwf DATA_PORT > nop > bcf ENABLE > return > ;----------- > EntryModeSet > btfsc BUSY_FLAG > goto EntryModeSet > bcf RS > bcf RW > movlw b'00000110' > call StrobeData > return > ;----------- > SendChar > btfsc BUSY_FLAG > goto SendChar > bsf RS > bcf RW > call StrobeData > return > ;----------- > ClearDisplay > btfsc BUSY_FLAG > goto ClearDisplay > bcf RS > bcf RW > movlw 0x01 > call StrobeData > return > ;----------- > HomeCursor > btfsc BUSY_FLAG > goto HomeCursor > bcf RS > bcf RW > movlw 0x02 > call StrobeData > return > ;----------- > DisplayOFF_CursorOFF_BlinkOFF > btfsc BUSY_FLAG > goto DisplayOFF_CursorOFF_BlinkOFF > bcf RS > bcf RW > movlw b'00001000' > call StrobeData > return > ;----------- > DisplayOFF_CursorOFF_BlinkON > btfsc BUSY_FLAG > goto DisplayOFF_CursorOFF_BlinkON > bcf RS > bcf RW > movlw b'00001001' > call StrobeData > return > ;----------- > DisplayOFF_CursorON_BlinkOFF > btfsc BUSY_FLAG > goto DisplayOFF_CursorON_BlinkOFF > bcf RS > bcf RW > movlw b'00001010' > call StrobeData > return > ;----------- > DisplayOFF_CursorON_BlinkON > btfsc BUSY_FLAG > goto DisplayOFF_CursorON_BlinkON > bcf RS > bcf RW > movlw b'00001011' > call StrobeData > return > ;----------- > DisplayON_CursorOFF_BlinkOFF > btfsc BUSY_FLAG > goto DisplayON_CursorOFF_BlinkOFF > bcf RS > bcf RW > movlw b'00001100' > call StrobeData > return > ;----------- > DisplayON_CursorOFF_BlinkON > btfsc BUSY_FLAG > goto DisplayON_CursorOFF_BlinkON > bcf RS > bcf RW > movlw b'00001101' > call StrobeData > return > ;----------- > DisplayON_CursorON_BlinkOFF > btfsc BUSY_FLAG > goto DisplayON_CursorON_BlinkOFF > bcf RS > bcf RW > movlw b'00001110' > call StrobeData > return > ;----------- > DisplayON_CursorON_BlinkON > btfsc BUSY_FLAG > goto DisplayON_CursorON_BlinkON > bcf RS > bcf RW > movlw b'00001111' > call StrobeData > return > ;----------- > END
Reply by ●February 4, 20042004-02-04
"Will" <larkmore@aol.com> wrote in message news:5faf6114.0402031434.38db8ce2@posting.google.com...> with 10KOhm pulldown resistors to ground on ALL of the lines on theI think one pin on the most PICs is open collector.
Reply by ●February 4, 20042004-02-04
"Meindert Sprang" <mhsprang@NOcustomSPAMware.nl> wrote in message news:<40209d2c$1@news.nb.nu>...> Your strobedata routine is too fast. Many LCD displays have a cycle time of > 500ns to 1000ns, where the E has to be kept high for 300 to 500ns or longer.I'm not sure how you're arriving at that conclusion. The formula I used to determine how long the enable pin strobed was as follows: For a PIC 20 MHz external resonator/crystal -> 5MHz instruction rate (clock/4) -> 200 ns per instruction. Even assuming worst case that the PIC sets the pin high at the very end of the BSF instruction and low at the very beginning of the BCF instruction, there are 3 instructions between them. At 200ns each, that's at least 600ns and possibly 800ns if everything lines up nicely. I've also checked it with a scope probe and it looks more than long enough. In fact, I have verified that the PIC is in fact sending the signals I thinnk it should be at the right timing, based upon the datasheet that Optrex had on their website. In case anyone cares, that file was Dmcman_full.pdf and had 58 pages. It had no revisions listed on the second page so I guess it was revision 0.
