Help with serial LCD project

[AGCB]

I'm trying to make a portable serial LCD module that I can easily hook up to any project
or PIC with just a few wires using a 74HC595 shift register.
I have used parallel LCDs so I know the basics of the routines. But I can not get this
to work. It assembles fine but the LCD won't initialize.
To give credit where due, my modified routines and hardware use parts and peices from
Nigel, Mike Predko, Blueteeth and probably others that I can't think of right now.
I wanted to try and do the code myself but now I believe it's time to ask for help.
Is there any obvious mistake in this code? I added longer delays to see if the LCD was
being hurried. Thanks. Aaron

;               Send data to LCD via  74HC595
;                                                                   Modified by Aaron
;  This Code Sends the data to the LCD in 4 Bit mode 
;
;  The data is shifted out to a 74HC595   The QD (Pin 3)goes to the
;   LCD's "RS" Bit.  Pins QE-QH (pins 4,5,6 & 7) go to the LCD pins D4 - D7
;    The LCD E pin is tied to the RCLK latch (pin 12)
;	Pins 8 & 13 of the 595 are grounded
;	Pins 16 Vcc and 10 SRCLR are tied to 5 v
;
;  Hardware Notes:
;    PWRT is Enabled.
;   The PIC is a 18F1220 Running at 4 MHz.
;   PortA.0 is the Data Bit
;   PortA.1 is the Clock Bit

	list	p=18F1220	;select device in configuration tab
	
	#include	<p18F1220.inc>	          ;   Runs at 4 MHz
	radix      dec

;  Register Usage
 CBLOCK 0x00C                   

 ENDC

;----------------------------  Define Inforation-----------------------------------
#DEFINE SData PORTA,0
#DEFINE Clock PORTA, 1
#DEFINE	STROBE	PORTA,2

;------------------  Macros---------------------------------------------
Clkstrobe MACRO		;  Strobe the Data Bit
	  bsf	 Clock
	  bcf	 Clock
	 ENDM
	
EStrobe MACRO			;  Strobe the "E" Bit
	  bsf	 Strobe
	  bcf	 Strobe
	 ENDM

;------------------------------------------------------------------------------
 
	config		osc = intio2, fscm = off, ieso = off	;1h
	config		pwrt = on, bor = on, borv = 27		;2L
	config		wdtps = 1, wdt = off			;2h
				;mclr enabled (default) 	;3h
	config		stvr = off, lvp = off, debug = off	;4L
				;default code protection off	;5L, 5h
				;default write protection off	;6L, 6h
				;default table read protection off ;7L, 7h

;----------------------------------------------------------------------------
	org	0x0000
	
	movlw	0x60		;internal osc 4.0 MHz
	movwf	osccon          ;                       pg 17
	bcf	adcon0,ADON	;turn off AD           pg 155
	setf	adcon1		;digital I/O           pg 156	
	clrf	trisa
	clrf	trisb		;all outputs
	clrf	latb		;
	clrf	portb		;all pins low
	clrf	porta
	movlb	0x01		;work in bank 1 GPRs
;----END OF BASIC INIT---------------------------------------------

;------------MAIN---------------------------------------------------
	call	SR_LCD_INIT
circle	goto	circle


;------------SUBS------------------------------------------------
SR_LCD_INIT
	call	del_1S
	movlw	0x30			;set 8 bit mode 1st   0011 0000
	call	LCD_CMD			;to make sure LCD is ready		

	movlw	0x20			;Set 4 bit mode   0010 0000
	call	LCD_Cmd

	movlw	0x28			;function set   0010 1000
	call	LCD_Cmd			;4 bit, 2 line, 5x7

	movlw	0x06			;Set display character entry mode  0000 0110
	call	LCD_Cmd			;increment, display shift off

	movlw	0x0c			;Set display on and cursor off command
	call	LCD_Cmd			;, 

	call	LCD_Clr			;clear display

	retlw	0x00

; ------command set routine-----------------------------------------------
	cblock
	templcd
	sendreg
	endc
LCD_Cmd		movwf	templcd
		swapf	templcd,w		;send upper nibble
		andlw	0x0f			;clear upper 4 bits of W
		call	ser_out
		
		EStrobe			;Pulse the E line high
		call	ms10
		movf	templcd,w		;send lower nibble
		andlw	0x0f			;clear upper 4 bits of W
		call	ser_out
		
		EStrobe			;Pulse the E line high
		call 	ms10
		retlw	0x00

;------------------------------------------------------------
ser_out	movwf	sendreg	;save copy of number
	movlw	0x08	;init 8 counter
	movwf	count
testbit	bcf	SData	;this is the data bit    '0' will be sent unless the next instruction 
						;  determines that a '1' should be sent instead
						
	btfsc	sendreg,7  	;is the MSb of sendreg  '0' or '1'
	bsf	SData    ;it's a '1' so set data bit to '1'        ;if not '1' then send '0'
	
	Clkstrobe		;clock it into 595 and shift register to next bit position
	call	ms10
	rlcf	sendreg,f  	;move to the next bit
	decfsz	count,f		;decrement bit counter
	goto	testbit		;if bit counter is not zero goto next bit	
	return		;done

;----------send character------------------------------------------------

LCD_CharD	addlw	0x30
LCD_Char	movwf	templcd
		swapf	templcd,w		;send upper nibble
		andlw	0x0f			;clear upper 4 bits of W
		IORLW	b'00010000'	;set the RS bit to data
		call	ser_out
		
		EStrobe			;Pulse the E line high

		movf	templcd,w		;send lower nibble
		andlw	0x0f			;clear upper 4 bits of W
		IORLW	b'00010000'	;set the RS bit to data
		call	ser_out
		
		EStrobe			;Pulse the E line high
		call 	Del_256
		retlw	0x00

;-----placement of 1st character---------------------------------

LCD_Line1	movlw	0x80			;move to 1st row, first column
		call	LCD_Cmd
		retlw	0x00

LCD_Line2	movlw	0xc0			;move to 2nd row, first column
		call	LCD_Cmd
		retlw	0x00

LCD_Line1W	addlw	0x80			;move to 1st row, column W
		call	LCD_Cmd
		retlw	0x00

LCD_Line2W	addlw	0xc0			;move to 2nd row, column W
		call	LCD_Cmd
		retlw	0x00

;----Basic house keeping---------------------------------------

LCD_CurOn	movlw	0x0d			;Set display on/off and cursor command
		call	LCD_Cmd
		retlw	0x00

LCD_CurOff	movlw	0x0c			;Set display on/off and cursor command
		call	LCD_Cmd
		retlw	0x00

LCD_Clr		movlw	0x01			;Clear display
		call	LCD_Cmd
		retlw	0x00

;------------DELAYS-------------------------------------------

;COMBO of sec and mS and  us  delays--------------------------

;-------------Adjustable delay-----1-255 seconds (4 1/4 min)
;                   ;enter with number of seconds in wreg before CALL
			;i.e.    movlw   d'xx'
	cblock
	bc1
	bc2
	bc3
	dc1
	dc2
	dc3
	secs
	endc
	
adj_delay_sec
	bcf	intcon,gie	;disable global interrupts   			
	movwf	secs			
repet	call	delay_ms
	decfsz	secs		;1 loop per number entered with in wreg
	goto	repet		;
	bsf	intcon,gie	;enable global interrupts
	return
	
delay_ms
	movlw	d'100'		;
        banksel bc3             ; Each loop here takes 1 SECOND  
        movwf   bc3             ;
dly2    movlw   .13             ; 
        movwf   bc2             ; 
        clrf    bc1             ; 
dly1    decfsz  bc1,f           ;
        goto    dly1		;
        decfsz  bc2,f           ; 
        goto    dly1		;            
        decfsz  bc3,f           ; 
        goto    dly2
        return
	
;------Adjustable delay-----10-2550ms(2.55 seconds)------------
                   ; delay = W x 10ms
			; enter with multiplier in WREG before CALL
				;i.e.  movlw   d'xx'

adj_delay_ms	
	bcf	intcon,gie	;disable global interrupts   ; delay W x 10ms
        banksel dc3                ; Wx10.015ms
        movwf   dc3             
dly2a    movlw   .13             ; repeat inner loop 13 times
        movwf   dc2             ; -> 13x(767+3)-1 = 10009 cycles
        clrf    dc1             ; inner loop = 256x3-1 = 767 cycles
dly1a    decfsz  dc1,f           
        goto    dly1a
        decfsz  dc2,f           ; end middle loop
        goto    dly1a            
        decfsz  dc3,f           ; end outer loop
        goto    dly2a
	bsf	intcon,gie	;enable global interrupts

        return

;---uS_delay   Range  75uS - 19,375uS   (19 mS) ?????????????????????


	;enter with <<desired delay devided by 75>> in W ('d' 1 - 255) 
	;round to nearest whole number

	;I.E.  desired delay = 750uS ÷ 75 = 10
	;I.E.     "    =5mS = 5000 uS ÷ 75 = 66.66 round to 67
			;before CALL instruction  ????????????????????	

	cblock
	cya
	cyb
	cyc
	endc
us_delay
	movwf	cya
	movlw	.25	;25 inner loops
	movwf	cyc
more	movf	cya,w
	movwf	cyb
	
		
cy1	decfsz	cyb	
	goto	cy1	
cy2	decfsz	cyc
	goto	more	
	return

;-------256 uS delay-----------------------
	cblock
	count
	endc
	
del_256	movlw	0xff
	movwf	count
repeat	decfsz	count,f
	goto	repeat
	return

;------------- "canned" common delays in seconds ----------------------

Del_1S	movlw	.1
	rcall	ADJ_DELAY_SEC
	return

Del_2S	movlw	.2
	rcall	ADJ_DELAY_SEC
	return

Del_3S	movlw	.3
	rcall	ADJ_DELAY_SEC
	return

Del_5S	movlw	.5
	rcall	ADJ_DELAY_SEC
	return

Del_10S	movlw	.10
	rcall	ADJ_DELAY_SEC
	return

;----Canned MS delays---------------------------------------

;---- 10 millisecond ------------
MS10	movlw	.1
	call	adj_delay_ms
	return

;---- 100 millisecond ------------
MS100	movlw	.10
	call	adj_delay_ms
	return

;---- 500 millisecond  (1/2 second)-------
MS500	movlw	.50	
	call	adj_delay_ms
	return

  	end

 

[Ian Rogers]

PM Mike Mclaren... He has done the best one I've seem

(Mike, K8LH)

 

[be80be]

Mike using a pic for his serial backpack its nice

 

[AGCB]

PM Mike Mclaren...

I know Mikes on the forum lots so I'll just wait for him to see this. Thanks Ian and Burt
Aaron

 

[Mike - K8LH]

PM Mike Mclaren... He has done the best one I've seem

(Mike, K8LH)

There's nothing I can do for him until he provides a proper schematic. The wiring descriptions in his code just don't make sense...

 

[AGCB]

I'm using this one from a 2008 thread. Aaron

 

[Mike - K8LH]

Hi Aaron,

Do you have a link to the 2008 thread, please? Do you know if anyone has a working interface based on that schematic?

 

[AGCB]

Mike
Let's see if this works
https://www.electro-tech-online.com/threads/74ls174-2-wire-lcd-interface.39640/

Post # 4

I'm open to other suggestions

 

[Mike - K8LH]

Hi Aaron,

Thanks for the link. Unfortunately I just don't see how that circuit could work since an RS signal level change through the '595 would not meet the tAS timing spec in the Hitachi HD44780 datasheet. Basically, unlike the LCD data lines which must be setup before the falling edge of the E strobe, the RS and R/W lines need to be setup before the rising edge of the E strobe. However, in that circuit an RS signal level change wouldn't show up at the LCD until after the E strobe rising edge.

If Blueteeth is around, maybe someone could ask him if that was a working circuit or just a concept?

Regards, Mike

 

[be80be]

There noway that could work and the code for it would be a nightmare If it did. Mike post the one you did with the new little pic

It's a way better setup.

Like this one it's nice real good job


And I have to say Mike does great work

Using a 595 saves pins but using a pic makes a smart serial LCD that can be uesd with plain Usart.

Which like my dryer board It uses serial for the display I used a serial LCD to test the temp and stuff,
But on the working model I used a serial seven segment to show only the time and the money.

 

[Mike - K8LH]

There are several examples of three wire 74HC595 backpacks out there. The DangerousPrototypes Bus Pirate LCD Adapter v2 only costs $9. You might also take a look at the three wire LCD adapter from Raj Bhatt over at Embedded-Lab.com.

 

[be80be]

This is a good layout

 

[languer]

Not sure if you were interested on a non-74HC595 design. But there is a PIC one with code here.

 

[AGCB]

Thanks for the replies. I'll try a different schematic and see what I can make work>
Aaron

 

[be80be]

The one from DangerousPrototypes would be the best. The pins are in logical order

 

[Mike - K8LH]

The one from DangerousPrototypes would be the best. The pins are in logical order

I agree but it also requires the most work from the software (you have to fill the shift register six times to write a single byte to the LCD)...

 

[Mr RB]

This design uses a 74HC595, and only needs one control wire from the PIC. It is a proven design and has been used to drive LCDs by many people in many projects;

**broken link removed**

https://www.romanblack.com/shift1.htm

 

[Mike - K8LH]

Does that design require filling the shift register six times to send a single byte to the LCD? How long would that take, 4-5 milliseconds?

 

[Mike - K8LH]

Aaron.

Please don't dismiss languer's suggestion for an "intelligent" serial LCD interface/backpack too quickly. While only requiring 1-pin for a serial interface is an obvious advantage, the cost savings in terms of code overhead on your host project shouldn't be overlooked. For example, a well designed intelligent serial LCD backpack should initialize the LCD to Hitachi HD44780 specs', which can save quite a bit of code space on your host.

In addition to the very nice serial LCD interface example provided by languer, here's another simple and relatively inexpensive serial interface example (below) which could be made into a tiny backpack or included on a project or development board;

Cheerful regards, Mike

 

[AGCB]

I'm nearly overwhelmed with all the good info I have received here. For the shear satisfaction (which some have mentioned) I think I will try to build a 595 SR version first. But the other options available with the PIC design make that, to me, a more logical (functionally) one. A thing I've noticed with sites that give any code examples at all are that they are usually written in C of which I know little.
But thanks for a boatload of good info.
Aaron