Thanks Mike,
That was quite innovative of you to use the incomming data to both talk to the PIC and control the RS line of the LCD!!
nice work.
So is your new design going to use a differend PIC with more I/O pins??
Dwight
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Re: How do you drive a Serial LCD?
Thanks Mike,
That was quite innovative of you to use the incomming data to both talk to the PIC and control the RS line of the LCD!!
nice work.
So is your new design going to use a differend PIC with more I/O pins??
Dwight
Dwight
These PIC's are like intricate puzzles just waiting for one to discover their secrets and MASTER their capabilities.
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Re: How do you drive a Serial LCD?
I'm upgrading the interface that uses the 8 pin PIC and actually studying another two slightly more advanced designs.So is your new design going to use a differend PIC with more I/O pins?
If you're interested, I've attached the source (assembler) for the 12F635 backpack as well as the source (also assembler) for the 16F1823 on that prototype board. This is the old software and, as I mentioned, probably not very useful for PBP users who are used to having all those wonderful LCD output formatting capabilities.
Happy Holidays! Mike
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Re: How do you drive a Serial LCD?
Hi Dwight (and gang),
If you're interested... I just finished testing the upgrade to the 8-pin PIC serial LCD interface and it works great. The mod involved adding an RC integrator/filter (10K + 330pF) between the GP0/D4 pin and the LCD RS pin. Now I can drive all six LCD control pins directly from the little 8-pin PIC which means I can collect serial data, analyze it, and write data to the LCD display any way I want. In short, you should be able to feed the serial interface using the DEBUG, SEROUT2 or HSEROUT commands with all of the same formatting parameters you're using now with the LCDOUT command. I'm pretty geeked (yes, I'm a nerd - LOL).
If anyone is interested, I'll start a new thread in the 'schematic' sub-forum after characterizing and testing the firmware. The only real advantages I can think of for this interface is its size (very small footprint on a project board when using the 2x5 header for a MikroE LCD Adapter board) and its ability to drive four lines of a switch matrix (one additional pin on the host can read four switches, an encoder, etc.).
Cheers, Happy Holidays, Mike
Last edited by Mike, K8LH; - 9th December 2011 at 19:47.
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Re: How do you drive a Serial LCD?
Drawing of the updated backpack hardware...
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Re: How do you drive a Serial LCD?
Hi Mike,
Mind if I ask what program you are using to illustrate your drawings?
Thanks,
BobK
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Re: How do you drive a Serial LCD?
Greetings BobK.
The drawings were made using the drawing tools in Excel...
The paper silkscreen on the Radio Shack prototyping board was a printout of the silkscreen layer from DipTrace. The paper silkscreen is laminated with plastic tape and glued onto the board.
Cheerful regards, Mike
Last edited by Mike, K8LH; - 14th December 2011 at 13:07.
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Re: How do you drive a Serial LCD?
Better late than never? Here's firmware for the 12F683 version of the serial backpack.
Cheerful regards, Mike
Code:;****************************************************************** ; * ; Filename: ezLCD v3 (12F683).asm * ; Author: Mike McLaren, K8LH * ; (C)2010: Micro Application Consultants, All Rights Reserved * ; Date: 08-Dec-11 (rev:111210.0637z) * ; * ; K8LH 12F683 serial HD44780 LCD 4-bit interface experiment * ; * ; 8-bit test code. this interface traps a 0xFE character and * ; writes the character immediately following it to the LCD as * ; a command character (RS = 0) * ; * ; * ; MPLab: 8.80 (tabs=8) * ; MPAsm: 5.43 * ; * ;****************************************************************** #include <p12f683.inc> list st=off errorlevel -302 radix dec __config _FCMEN_OFF&_IESO_OFF&_MCLRE_OFF&_WDT_OFF&_INTRC_OSC_NOCLKOUT ;--< variables >--------------------------------------------------- datahi equ 0x40 ; shadow for 1st nibble datalo equ 0x41 ; shadow for 2nd nibble temp equ 0x42 ; low level LCD routines delayhi equ 0x43 ; rsflag equ 0x44 ; ;--< constants >--------------------------------------------------- ; ; bit time (cycles) used to sample a serial bit stream ; ; 9600 baud, 208 (208.3) cycles, 0.16% bit rate error ; 19200 baud, 104 (104.2) cycles, 0.16% bit rate error ; 57600 baud, 35 ( 34.7) cycles, 0.80% bit rate error ; clock equ 8 ; 8 MHz clock usecs equ clock/4 ; cycles/usec multiplier msecs equ clock/4*1000 ; cycles/msec multiplier bRate equ 57600 ; baudrate 9600, 19200, or 57600 bTime equ (usecs*10000000/bRate+5)/10 ; bTime = 208, 104, or 35 cycles ; #define D4 0 ; GP0 -> LCD 'D4' #define D5 1 ; GP1 -> LCD 'D5' #define D6 2 ; GP2 -> LCD 'D6' #define SerPin GPIO,3 ; GP3 -> Serial Input #define D7 4 ; GP4 -> LCD 'D7' #define E 5 ; GP5 -> LCD 'E' #define RS D4 ; RS 'rc' integrator output ;--< macros >------------------------------------------------------ ; ; inDlyCy() in-line delay macro, range 0..1023 cycles, ; produces 0 to 6 instructions. ; inDlyCy macro pTime local dloop if pTime > 3 movlw (pTime)/4-1 ; dloop addlw -1 ; bc dloop ; endif if pTime%4 & 1 nop ; 1 cycle endif if pTime%4 & 2 goto $+1 ; 2 cycles endif endm ; ; K8LH DelayCy() subsystem macro generates four instructions ; DelayCy macro cycles ; 11..327690 cycle range if (cycles<11)|(cycles>(5*65536+10)) error " DelayCy range error " endif movlw high((cycles-11)/5)+1 movwf delayhi movlw low ((cycles-11)/5) call uDelay-((cycles-11)%5) endm ;****************************************************************** ; Reset Vector * ;****************************************************************** org 0x0000 v_reset clrf STATUS ; |B0 goto Main ; |B0 ;****************************************************************** ; Interrupt Vector * ;****************************************************************** org 0x0004 v_int ; ; using IOC interrupt on start bit leading edge ; inDlyCy(bTime/2-4) ; half bit time minus 4 cycles |B0 movlw 1<<E ; preset E bit |B0 movwf datahi ; |B0 movwf datalo ; |B0 ; ; collect lo nibble in 'datalo' (LCD data bits b0..b3) ; bit0 inDlyCy(bTime-3) ; |B0 btfsc SerPin ; bit = 0? yes, skip, else |B0 bsf datalo,D4 ; set LCD D4 shadow bit |B0 bit1 inDlyCy(bTime-2) ; |B0 btfsc SerPin ; bit = 0? yes, skip, else |B0 bsf datalo,D5 ; set LCD D5 shadow bit |B0 bit2 inDlyCy(bTime-2) ; |B0 btfsc SerPin ; bit = 0? yes, skip, else |B0 bsf datalo,D6 ; set LCD D6 shadow bit |B0 bit3 inDlyCy(bTime-2) ; |B0 btfsc SerPin ; bit = 0? yes, skip, else |B0 bsf datalo,D7 ; set LCD D7 shadow bit |B0 ; ; collect hi nibble in 'datahi' (LCD data bits b4..b7) ; bit4 inDlyCy(bTime-2) ; |B0 btfsc SerPin ; bit = 0? yes, skip, else |B0 bsf datahi,D4 ; set LCD D4 shadow bit |B0 bit5 inDlyCy(bTime-2) ; |B0 btfsc SerPin ; bit = 0? yes, skip, else |B0 bsf datahi,D5 ; set LCD D5 shadow bit |B0 bit6 inDlyCy(bTime-2) ; |B0 btfsc SerPin ; bit = 0? yes, skip, else |B0 bsf datahi,D6 ; set LCD D6 shadow bit |B0 bit7 inDlyCy(bTime-2) ; |B0 btfsc SerPin ; bit = 0? yes, skip, else |B0 bsf datahi,D7 ; set LCD D7 shadow bit |B0 ; ; if(datahi == 0x0F) // if data == 0xF0..0xFF ; { datahi.E = 0; // don't write LCD (E bit off) ; datalo.E = 0; // don't write LCD (E bit off) ; } // ; gpio = rsflag; // charge or drain RS cap ; delay_us(3); // ; gpio = datahi; // setup D4..D7 and E=1 ; gpio.E = 0; // E = 0 (write LCD) ; gpio = rsflag; // charge or drain RS cap ; delay_us(3); // ; gpio = datalo; // setup D4..D7 and E=1 ; gpio.E = 0; // E = 0 (write LCD) ; ; rsflag ^= 1<<RS; // toggle rs flag ; if(datahi.E) // if not 0xFE character ; rsflag = 1<<RS; // reset rs flag (RS=1) ; wrhi movf rsflag,W ; the RS bit flag & mask |B0 movwf GPIO ; charge or drain RS cap |B0 movlw b'00110111' ; mask for datahi = 0x0F |B0 -- xorwf datahi,W ; is data == 0xF0..0xFF? |B0 -- skpnz ; no, skip, else |B0 -- bcf datahi,E ; don't write LCD |B0 -- skpnz ; no, skip, else |B0 -- bcf datalo,E ; don't write LCD |B0 -- movf datahi,W ; get data 7..4 bits |B0 movwf GPIO ; setup D4..D7, E=1 |B0 bcf GPIO,E ; E = 0 (write LCD) |B0 wrlo movf rsflag,W ; the RS bit flag & mask |B0 movwf GPIO ; charge or drain RS cap |B0 movlw 1<<RS ; |B0 -- xorwf rsflag,F ; toggle RS flag & mask |B0 -- btfsc datahi,E ; if datahi not 0x0F |B0 -- iorwf rsflag,F ; reset RS flag & mask (RS=1) |B0 -- goto $+1 ; |B0 -- movf datalo,W ; get data 3..0 bits |B0 movwf GPIO ; setup D4..D7, E = 1 |B0 bcf GPIO,E ; E = 0 (write LCD) |B0 stop inDlyCy(bTime-24) ; during middle of stop bit |B0 movf GPIO,W ; clear IOC mismatch |B0 bcf INTCON,GPIF ; clear IOC interrupt flag |B0 retfie ; |B0 ;****************************************************************** ; main * ;****************************************************************** ; ; void main() ; { ; cmcon0 = 7; // comparator off ; gpio = 0; // clear gpio output latches ; trisio = 0b00001000; // gp3 input, others outputs ; osccon = 0b01110000; // setup intosc for 8 MHz ; while(osccon.HTS == 0); // wait for osc stable ; Main movlw b'00000111' ; |B0 movwf CMCON0 ; comparator off |B0 clrf GPIO ; clear GPIO output latches |B0 bsf STATUS,RP0 ; bank 1 |B1 ; clrf ANSEL ; no analog, all digital |B1 movlw b'00001000' ; GP3 input, all others outputs |B1 movwf TRISIO ; |B1 movwf IOCA ; enable IOC for GP3 'SerPin' |B1 movlw b'01110000' ; |B1 movwf OSCCON ; 8-mhz INTOSC system clock |B1 stable btfss OSCCON,HTS ; oscillator stable? |B1 goto stable ; no, branch, else |B1 ; ; HD44780 "initialize by instruction" for 4-bit interface mode ; bcf STATUS,RP0 ; bank 0 |B0 DelayCy(50*msecs) ; LCD 50 msec 'power up' reset |B0 movlw 0x03 ; hi nibble of "8-bit" command |B0 call PutNyb ; step 1 (send nibble only) |B0 DelayCy(4*msecs) ; required 4 msec delay |B0 movlw 0x03 ; |B0 call PutNyb ; step 2 (send nibble only) |B0 DelayCy(160*usecs) ; required 160-us delay |B0 movlw 0x03 ; |B0 call PutNyb ; step 3 (send nibble only) |B0 DelayCy(160*usecs) ; required 160-us delay |B0 movlw 0x02 ; hi nibble of "4-bit" command |B0 call PutNyb ; select 4-bit interface mode |B0 DelayCy(160*usecs) ; required 160-us delay |B0 ; ; now in 4-bit interface mode. ok to send full bytes. ; movlw 0x28 ; 4-bit, 2-lines, 5x7 font |B0 call PutCmd ; send "function set" command |B0 movlw 0x0C ; display on, cursor & blink off |B0 call PutCmd ; send "display on/off" command |B0 movlw 0x06 ; cursor inc, shift off |B0 call PutCmd ; send "entry mode set" command |B0 movlw 0x01 ; clear display (1.53-msecs) |B0 call PutCmd ; send "entry mode set" command |B0 DelayCy(1530*usecs) ; 1.53 msec delay for "clear" |B0 ; ; // setup RA3 'SerPin' for interrupt-on-change ; ; rsflag = 1<<RS; // set RS flag & mask ; while(SerPin == 0); // wait for hi level on GP3 ; temp = gpio; // clear any mismatch condx ; intcon.RAIF = 0; // clear IOC interrupt flag ; ioca.IOCA3 = 1; // eanble IOC for GP3 'SerPin' ; intcon.GIE = 1; // enable global interrupts ; ; while(1); // loop forever ; } ; bcf STATUS,RP0 ; bank 0 |B0 movlw 1<<RS ; |B0 movwf rsflag ; set RS flag & mask (RS=1) |B0 btfss SerPin ; stop state? yes, skip, else |B0 goto $-1 ; loop (wait) |B0 movf GPIO,W ; clear GPIO mismatch condition |B0 bcf INTCON,GPIF ; clear IOC interrupt flag |B0 bsf INTCON,GIE ; enable global interrupts |B0 bsf INTCON,GPIE ; enable 'IOC' interrupts |B0 loop goto loop ; loop forever |B0 ;****************************************************************** ; low level lcd subroutines * ;****************************************************************** PutCmd ; entry point for "cmd" data clrc ; RS = 0 (command) |B? skpnc ; skip unconditionally |B? PutDat ; entry point for "dat" data setc ; RS = 1 (data) |B? banksel temp ; bank 0 |B0 movwf temp ; save WREG data byte |B0 swapf temp,W ; |B0 call PutNyb ; send hi nybble |B0 swapf temp,W ; |B0 call PutNyb ; send lo nybble |B0 DelayCy(50*usecs) ; required between writes |B0 return ; |B0 PutNyb movwf temp ; |B0 bcf GPIO,RS ; RS = 0 (discharge RS cap) |B0 skpnc ; RS = 0? yes, skip, else |B0 bsf GPIO,RS ; RS = 1 (charge RS cap) |B0 movlw 1<<E ; |B0 btfsc temp,0 ; |B0 iorlw 1<<D4 ; |B0 btfsc temp,1 ; b1 = 0? yes, skip, else |B0 iorlw 1<<D5 ; |B0 btfsc temp,2 ; b2 = 0? yes, skip, else |B0 iorlw 1<<D6 ; |B0 btfsc temp,3 ; b3 = 0? yes, skip, else |B0 iorlw 1<<D7 ; |B0 movwf GPIO ; LCD D4..D7 = data1, E = 1 |B0 bcf GPIO,E ; E = 0 |B0 return ; |B0 ;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ; K8LH DelayCy() 16-bit uDelay subroutine ~ ;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ nop ; entry for (delay-11)%5 == 4 |B0 nop ; entry for (delay-11)%5 == 3 |B0 nop ; entry for (delay-11)%5 == 2 |B0 nop ; entry for (delay-11)%5 == 1 |B0 uDelay addlw -1 ; subtract 5 cycle loop time |B0 skpc ; borrow? no, skip, else |B0 decfsz delayhi,F ; done? yes, skip, else |B0 goto uDelay ; do another loop |B0 return ; return with C = Z = 0 |B0 ;****************************************************************** end
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