NEW! |
Another simple Hitachi LCD display control routine. This ASM code can drive a display with a PIC16F628 with the control lines on any PORTB pins - the actual connection are easily redefined in the code by changing the initial definitions.
; LCD driver by Barry (tron at zoidberg dot nl) include p16f628.inc list p=16f628 __config (_CP_OFF & _DATA_CP_OFF & _PWRTE_ON & _WDT_OFF & _INTRC_OSC_CLKOUT & _LVP_OFF & _BODEN_OFF & _MCLRE_OFF) ; LCD control lines #define LCD_RS 5 ; 0 = Command, 1 = Data #define LCD_RW 6 ; 0 = Write, 1 = Read #define LCD_E 4 ; 1 to send data #define LCD_D4 0 ; 4 data lines #define LCD_D5 1 #define LCD_D6 2 #define LCD_D7 3 ; Registers we will be using #define R_DEL1 0x20 ; Delay register #define R_DEL2 0x21 ; Delay register #define R_WDATA_TMP1 0x22 #define R_WDATA_TMP2 0x23 #define R_SEND_W_TMP 0x24 #define R_WTMP 0x27 ; W storage #define R_STMP 0x28 ; STATUS storage #define R_STMP1 0x2E ; Send temp register #define R_PSEC 0x2F org 0 goto init ; Blank interrupt routine - simply saves and restores status & W ; Add code to do something useful... org 4 movwf R_WTMP ; Save W & STATUS swapf STATUS, W movwf R_STMP bcf STATUS, RP0 int_cleanup: movlw b'11111000' ; Clear interrupt bits andwf INTCON, F swapf R_STMP, W ; Restore W & STATUS movwf STATUS swapf R_WTMP, F swapf R_WTMP, W retfie ; Init sets all I/O lines as outputs and selects PORTA as ; I/O lines by turning the comparators off. init: clrf PORTB clrf PORTA movlw 0x07 movwf CMCON ; Comparators off - PORTA on bsf STATUS, RP0 ; Select bank 1 movlw b'00000000' ; Select PORTB as outputs movwf TRISB movlw b'00000000' ; Select PORTA as outputs movwf TRISA bcf STATUS, RP0 ; Select bank 0 ; Begin the LCD initialisation ; Power up timer should give delay, but do it anyway movlw 0x14 call delay ; Send the command to select 4-bit mode first bcf PORTB, LCD_RS bcf PORTB, LCD_RW movlw 0x02 ; Still in 8-bit, so appears as 0x20 to LCD call w_to_data call pulse_e ; Should now be in 4-bit mode - send init movlw b'00101000' call send_w movlw b'00001110' call send_w movlw b'00000110' call send_w main_loop: bcf PORTB, LCD_RS ; Command mode movlw b'00000010' ; Return cursor to home call send_w bsf PORTB, LCD_RS ; Data mode call delay_1ms ; Takes a couple of ms movlw 'H' call send_w movlw 'e' call send_w movlw 'l' call send_w movlw 'l' call send_w movlw 'o' call send_w movlw '!' call send_w goto main_loop ; ---------------------- send_w movwf R_SEND_W_TMP swapf R_SEND_W_TMP, F movlw 0x0F andwf R_SEND_W_TMP, W call w_to_data call pulse_e swapf R_SEND_W_TMP, F movlw 0x0F andwf R_SEND_W_TMP, W call w_to_data call pulse_e return w_to_data movwf R_WDATA_TMP1 movf PORTB, W movwf R_WDATA_TMP2 bcf R_WDATA_TMP2, LCD_D4 bcf R_WDATA_TMP2, LCD_D5 bcf R_WDATA_TMP2, LCD_D6 bcf R_WDATA_TMP2, LCD_D7 btfsc R_WDATA_TMP1, 0 bsf R_WDATA_TMP2, LCD_D4 btfsc R_WDATA_TMP1, 1 bsf R_WDATA_TMP2, LCD_D5 btfsc R_WDATA_TMP1, 2 bsf R_WDATA_TMP2, LCD_D6 btfsc R_WDATA_TMP1, 3 bsf R_WDATA_TMP2, LCD_D7 movf R_WDATA_TMP2, W movwf PORTB return pulse_e bsf PORTB, LCD_E nop nop nop nop bcf PORTB, LCD_E call delay_1ms call delay_1ms return ; Calls the delay_1ms routine the number of times specified by ; the W register. delay movwf R_DEL2 delay_loop call delay_1ms decfsz R_DEL2, F goto delay_loop return ; When called gives a delay of about 1000 cycles, or 1ms at 4Mhz ; before the next instruction is executed. delay_1ms movlw d'248' movwf R_DEL1 delay_1ms_loop nop decfsz R_DEL1, F goto delay_1ms_loop return end
Stephen
van Schalkwyk Says: " I am quite new to
microprocessors and this code is going to be a great help - many thanks!
Stephen " +
file: /Techref/microchip/4bitlcd-b.htm, 4KB, , updated: 2010/7/2 16:39, local time: 2024/10/4 07:52,
owner: RAK-a_kats-U,
35.171.164.77:LOG IN ©2024 PLEASE DON'T RIP! THIS SITE CLOSES OCT 28, 2024 SO LONG AND THANKS FOR ALL THE FISH!
|
©2024 These pages are served without commercial sponsorship. (No popup ads, etc...).Bandwidth abuse increases hosting cost forcing sponsorship or shutdown. This server aggressively defends against automated copying for any reason including offline viewing, duplication, etc... Please respect this requirement and DO NOT RIP THIS SITE. Questions? <A HREF="http://www.massmind.org/techref/microchip/4bitlcd-b.htm"> PIC 4 bit 16x2 Hitachi LCD driver by Barry</A> |
Did you find what you needed? |
Welcome to massmind.org! |
Welcome to www.massmind.org! |
.