View Full Version : LCDOUT w/custom interface?

Mike, K8LH
- 20th September 2009, 16:23
Someone on another Forum asked me if it's possible to use the LCDOUT function with my old Novelty Serial LCD Interface (a simple 1-pin interface experiment inspired by the Predko 2-pin shift-register interface).

The interface uses standard Async' Serial data but in a rather exotic format where each byte is sent as two bytes, one nybble per byte, along with the LCD 'RS' bit.

; host low level K8LH Novelty 12F635 Serial LCD Driver
clrc ; C = RS = 0, 'command' |B0
skpnc ; |B0
setc ; C = RS = 1, 'data' |B0
movwf Temp ; save data in WREG |B0
swapf Temp,W ; swap nybbles -> WREG |B0
call LcdNyb ; send left nybble |B0
movf Temp,W ; send right nybble |B0
andlw 0x0F ; mask off left nybble |B0
skpnc ; RS = 0? yes, skip, else |B0
iorlw b'11000000' ; set the RS bits |B0
btfss PIR1,TXIF ; transmit buffer empty? |B0
goto $-1 ; no, branch, else |B0
movwf TXREG ; send byte |B0
return ; |B0

Can the LCDOUT function use a custom driver like the one above (after being upgraded to catch the special $FE character)?

Kind regards, Mike

- 20th September 2009, 20:12
I must be missing the point. If it is wired as shown just use the normal LCDOUT. ???

How is the 2 pin or 1 pin thing you mention wired?

- 12th October 2009, 16:06
Hi, Dave

I think this might be some kind of serial to parallell converter ... trying to use the minimum pin count device ...

might be used for a very particular use ...

The Question was " Can I use THAT with PBP "LCDOUT" Command ??? "

so, the answer is NO ...

May be some SEROUT2 with modifier for 4 bits data out ... ( to be confirmed )


- 12th October 2009, 16:46
May be some SEROUT2 with modifier for 4 bits data out ... ( to be confirmed )

OK, I see what I was missing now. This is a LCD Backpack thing.

- 3rd March 2015, 04:54
RA4 is an open drain output.
You'll need a pull-up resistor on that pin.