12f675_fuse_about_to_blow!

[LEDave]

Have tweaked the DATAUS and can see pretty much all the characters, cheers.

I'm slightly embarrassed but I'll fess-up. I'm still having a problem with the back-light.

The display pdf shows the Anode / cathode on pins 15 / 16 with the current as below:

With B/L ILED VLED=5.0V -- 72 80 mA

So I'm thinking at 5v with 75ma a 60 ohm resistor on pin 15, pin 16 ground should do it.

I always thought LED's worked on about 25ma, must be a big LED inside then?

Dave

[Byte_Butcher]

So I'm thinking at 5v with 75ma a 60 ohm resistor on pin 15, pin 16 ground should do it.

I always thought LED's worked on about 25ma, must be a big LED inside then?

Dave

It may have one big LED, or several smaller ones in parallel.
I have some Lumex displays that are rated for up to 160mA. But they are viciously bright at that level and I rarely run them at more than 50mA.
For dim lighting conditions, I may run them at 20mA..

I'd start with about 1/2 current and see how it goes. No need to run them any harder than necessary. If you've got 100 ohms, or 200 even, give it a go.

Don't forget that resistor wattage... a 60 ohm resistor @ 75mA = 0.3375 watts dissipated.

Steve

[LEDave]

Thanks for that Steve.

I'll start with 200ohms. Just to double check that goes to the anode pin 15 right?

Dave (Mr Windy).

[mackrackit]

It does not matter, 15 or 16.

[LEDave]

Finaly managed to find five minutes to connect the back-light up using a 150ohm
resistor, however:

Before connection I had 4 lines of text. Then I connected the back-light which came on a nice blue colour but the text vanished. I then disconnected the back-light,the text didn't reappear, reloaded the program still no text (with or without the back-light on). I then loaded the program into my other 16F684 with the same outcome

Could it be the DATAUS number again?

Or something more worrying.

Dave

[HenrikOlsson]

Hmmm, from where do you pull the current for the backlight and is that supply rated/capable of supplying the current? Measure the voltage as you turn on the backlight and see if it sags.

Do you have a PAUSE at the beginning of the program to allow the LCD to boot up properly before writing to it? Something like PAUSE 1000 or whatever....

/Henrik.

[LEDave]

Hi Henrik

I've measured the voltage, it doesn't blip from 4.6v, even when the back-light is switched off - on.

I added the pause.Still no text showing.

Here's the program:

ANSEL   = %00000000    'Disable analog select so ports work as digital i/o.
CMCON0  = %00000111    'Disable analog comparators.
TRISA   = %00000000    'Set PORTA as OUTPUT.
PORTA   = %00000000    'Set PORTA pins all low.
TRISC   = %00000000    'Set PORTC as OUTPUT.
PORTC   = %00000000    'Set PORTC pins all low.

DEFINE LCD_DREG     PORTC    'PORTC.0 WILL CONNECT TO DB4, PORTC3 TO DB7
DEFINE LCD_DBIT     0
DEFINE LCD_RSREG    PORTC
DEFINE LCD_RSBIT    4        'PORTC.4 CONNECT TO LCD PIN4
DEFINE LCD_EREG     PORTC
DEFINE LCD_EBIT     5         'PORTC.5 CONNECT TO LCD PIN6
DEFINE LCD_BITS     4
DEFINE LCD_LINES    4
DEFINE LCD_COMMANDUS 2000     
DEFINE LCD_DATAUS 75

DEFINE OSC 4

MAIN:
PAUSE 1500
LCDOUT $FE,1,"*Hello WORLD*!"
LCDOUT $FE,$C0,"I't WORKS!"
LCDOUT $FE,$94,"I't WORKS!"
LCDOUT $FE,$d4,"Oh dear it stopped!"
GOTO MAIN

Dave