Busy flag problems with CFAH2004A-GGB-JP

A

azzman

New member
I am having a problem with the busy flag never clearing (always stays high)

CFAH2004A-GGB-JP

this is my init code.
notes:
-delayshort is about a 500ms delay.
-blink is a simple routine to blink an led.
-lcdputcmd2 sends the value in w to the lcd without checking the busy flag.
-lcdputcmd sends the value after checking the busy flag


LCDINIT

; Busy-flag is not yet valid
CLRF LCD_CTRL ; ALL PORTA output should output Low.

call blink
call blinkfast

MOVLW 0x038 ; 8-bit-interface, 2-lines
call LCDPUTCMD2

call blink
call blink

MOVLW 0x038 ; 8-bit-interface, 2-lines
call LCDPUTCMD2
call DELAYSHORT
MOVLW 0x038 ; 8-bit-interface, 2-lines
call LCDPUTCMD2
call DELAYSHORT


; bsf LCD_CTRL, LCD_E
; call DELAYSHORT
; bcf LCD_CTRL, LCD_E

call blink
call blinkfast

MOVLW 0x038 ; 8-bit-interface, 2-lines
call LCDPUTCMD2



MOVLW 0x008 ; disp.off, curs.off, no-blink
call LCDPUTCMD

call blink
call blink

movlw 0x001
call LCDPUTCMD

MOVLW 0x006 ; Entry Mode
call LCDPUTCMD

MOVLW 0x00C ; Display On Cursor Off
call LCDPUTCMD
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C

cosmicvoid

Master
You should post the code for the LCDPUTCMD routine.

I was looking at some old code of mine for character mode displays, and I was amused to see that in my busy check routine, I had added a counter in the loop, so the routine would bail out after a while if the flag never went low. I guess that the busy flag was not all that reliable ;) .
 
CF Tech

CF Tech

Administrator
I have a timeout on the busy flag too. Not because I have ever seen it be unreliable, but if the code hangs indefinitely because of a bad LCD, your debugging is shot. If the code is smart enough to give up on the busy flag after a maximum possible delay then other functions in the system will work, and the symptoms will start pointing to the LCD system.
 
A

azzman

New member
here are the lcdputcmd and lcdbusy routines.

so is it safe to say that i got a bad lcd at this point?


LCDPUTCMD
MOVWF LCD_TEMP
CALL LCDBUSY
BCF LCD_CTRL, LCD_RW
BCF LCD_CTRL, LCD_RS
BSF LCD_CTRL, LCD_E
MOVF LCD_TEMP, W
MOVWF LCD_DATA
BCF LCD_CTRL, LCD_E
RETURN

LCDBUSY
BSF STATUS,RP0
MOVLW 0x0FF
MOVWF TRISB
BCF STATUS,RP0
BCF LCD_CTRL, LCD_RS
BSF LCD_CTRL, LCD_RW
BSF LCD_CTRL, LCD_E
MOVF LCD_DATA, W
BCF LCD_CTRL, LCD_E
ANDLW 0x80
BTFSS STATUS, Z
GOTO LCDBUSY
LCDNOTBUSY
BCF LCD_CTRL, LCD_RW
BSF STATUS,RP0
MOVLW 0x000
MOVWF TRISB
BCF STATUS,RP0

RETURN
 
CF Tech

CF Tech

Administrator
I am not real familiar with the PIC instructions, but I think that the "BTFSS" is wrong. You want to loop if the busy is a one, and skip the loop instruction if the busy is 0. Try replacing it with a "BTFSC".
 
A

azzman

New member
this is lcdputcmd2. it takes out lcdbusy and puts in huge delays.

this is to bypass the busy flag altogether. I tried changing btfss to btfsc. didn't work...

any suggestions? do i have a bad lcd?


LCDPUTCMD2
MOVWF LCD_TEMP ; Command to be sent is in W
BCF LCD_CTRL, LCD_RW ; Set LCD in read mode
BCF LCD_CTRL, LCD_RS ; Set LCD in command mode
MOVF LCD_TEMP, W
MOVWF LCD_DATA ; Send data to LCD
CALL DELAY1S
BSF LCD_CTRL, LCD_E ; LCD E-line High
CALL DELAY1S
BCF LCD_CTRL, LCD_E ; LCD E-line Low
CALL DELAY1S
RETURN
 
C

cosmicvoid

Master
I am not going to analyze your code too closely, as I hate the PIC instruction set.

One comment for the routine that uses fixed delays... the longest command execution time is only 1.53 mS, so a 2 mS delay would be adequate.

Another thought, depending on your cpu clock rate, is that you may have an E pulse width that is too short. The spec says 150 nS minimum. In the version with busy test, there is only one instruction between the E set and E clear. If you have a 20 MHz clock (50 nS cycle time) then the E width would only be 100 nS. What's your clock speed? Have you checked the E width?
 
A

azzman

New member
ok i feel really stupid

after hooking my breadboard to an agilent logic analyzer i found my problem to be that i didn't set my PORTA to be output.

sorry for troubling you guys over this
 
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