LCD cable length?

[Art]

Will do, thanks
I think I'll have to.

[Art]

A little problem...
Installed the hijack routines and the two files in PBP directory.
When I use the include file for lcdanypin, I get an error (using MPASM)
for line 87 which is this line:
LOW LCD_RS : HIGH LCD_E

If I comment that out I then get a lot of errors

[Darrel Taylor]

LCD_RS and LCD_E should be declared in your program, along with the other LCD pins.
Something like ...

;----[ Change these to match your LCD ]--------------------------------------- 
LCD_DB4    VAR PORTA.0 
LCD_DB5    VAR PORTB.3 
LCD_DB6    VAR PORTB.7 
LCD_DB7    VAR PORTC.1 
LCD_RS     VAR PORTD.4 
LCD_E      VAR PORTA.1 
LCD_Lines  CON 2 ' # of Lines on LCD, 1 or 2 (Note: use 2 for 4 lines) 
LCD_DATAUS CON 50 ' Data delay time in us 
LCD_COMMANDUS CON 2000 ' Command delay time in us 
INCLUDE "LCD_AnyPin.pbp" ; *** Include MUST be AFTER LCD Pin assignments ****

[Art]

Oops!

[Art]

Bah! Still not having much luck here,
I have the LCD routines working, and changed the LCD_anypin file as follows:

;===============( DO NOT Change anything below this line )====================
;----[Virtual LCD Port --- 4bit mode]-----------------------------------------
ASM
LCD_Port_HNIB  macro           ; Port definition for LCD High Nibble
    Vbit   LCDCDFLAG, _LCD_RS  ; Select Command/Data register
    Vpin   4, _LCD_DB4         ; Put the High Nibble on the bus
    Vpin   5, _LCD_DB5
    Vpin   6, _LCD_DB6
    Vpin   7, _LCD_DB7
    PulseLow  _LCD_E, 5        ; pulse the Enable Pin for 2 us
  endm
;-----------------------    
LCD_Port_LNIB  macro           ; Port definition for LCD Low Nibble 
    Vpin   0, _LCD_DB4         ; Put the Low Nibble on the bus
    Vpin   1, _LCD_DB5
    Vpin   2, _LCD_DB6
    Vpin   3, _LCD_DB7
    PulseLow  _LCD_E, 5        ; pulse the Enable Pin for 2 us
  endm
ENDASM

Since I'm only using a single display, hopefully that's all that is needed to enable the E pin for 5us.
Still the display coming on at all after startup is hit & miss.
It seems to come on straight after programming with the pickit2 (when powered by the pickit2,
but doesn't want to come on when powered by any other means (or even by the pickit2 when not being programmed).

[Art]

Seems the problem is hardware Darrel!

I wanted the pic to be able to switch on & off power to the LCD, so I used a BD649 transistor to switch the ground pin of the LCD display.

The base is connected via 2.2K resistor to a spare pic pin, collector to the LCD ground, and emitter connected to the circuit ground.
Then the idea was to set the pic pin connected to base high, and then wait the "PAUSE 1000" delay time for the LCD to be ready each time I used it.
If I now short the emitter and collector of the BD649 while powering up, the display works every time (with LCD_anypin).

I can then release the short between the transistor pins, and the display stays on! What's happening there?

It's probably become obvious it's for a car circuit.
The idea is to have the LCD (VFD) powered only when the car is started, but the pic circuit should be running all the time.

[Darrel Taylor]

Maybe ...

If the data/RS/E pins are not tri-stated while the power to the VFD is OFF, it could be trying to power it from those pins.
Then when the transistor turns on, it doesn't activate the power-on reset in the display.

When programming with the PICkit, those pins will always tri-state during programming.

Just turning off the transistor without tri-stating all the pins first may not be enough.
Then remember to clear the FLAGS variable, so PBP will re-initialize the display.