dim lcd

happybenguy · Joined: 22 Apr 2005 Posts: 5

hi all. I just got my first lcd screen in and got it all hooked up today. Its a 16*1a. I am using bascom avr and am using the lcd functions. I got the lcd to come on and to display text but the text is really dim. I have the contrast pin connected to ground so that should be ok. I couldnt get it to have the characters show up darker, so i hooked it up all 8 bits and the rs and e line and wrote my own little lcd program that initializes and sends data to the lcd. That worked well and the characters were nice and dark, so i know the lcd works fine, but when i have it hooked up in 4 bit mode and use the bascom lcd functions i cannot get it to display the characters nice and dark like they were when i had it hooked up the other way. I would really like to be able to use the lcd function in bascom because doing it all manually takes forever. If anyone could help me that would be really great. Thanks

DToolan · Posted: Fri Apr 22, 2005 4:33 am Post subject:

I would use a pot to vary contrast. I've never had a problem with the following 4-bit connect... here

happybenguy · Joined: 22 Apr 2005 Posts: 5

well i tried the pot but it didnt fix the problem. I know i have everything hooked up right but im starting to think that it works well in 8bit mode and not so well in 4bit mode because it was a cheap lcd and i maybe have a low duty cycle in 4 bit mode due to the fact that it must right each character using two cycles instead of one. Im purdy sure that is whats going on so i am woundering if there is a way that i can use the basom lcd commands but output using all 8 lines from portb instead of using 4 then maybe have the rs and enable bits on porta or somthing. Is that possible? thanks for your help.

Duval JP · Joined: 22 Jun 2004 Posts: 1198 Location: France

Hi,
Would you please add
The type of µcontroler of your LCD
the type of µcontroler used (Atmega, tiny...)
speed Xtal...
a brief of the config you did
the statments you use...

did you use the IDE options\compiler\lcd or did you program it ?

But I confirm Bascom works without any Pb to drive LCD. 1, 2, 4 lines is OK

JP

happybenguy · Joined: 22 Apr 2005 Posts: 5

alrighty, here goes

lcd controller is a ks0066u, same thing as the stanard controlers as far as i can tell

got it hooked up to a mega32

using the internal rc at 8mhz

this program is the one that i hooked up in 4 bit mode and used the basom functions with and uses the lcd settings from the options menu which are set for my lcd. 16x1a-4bit-port

Duval JP · Joined: 22 Jun 2004 Posts: 1198 Location: France

did you unselect the JTAG ?
Port C is not working correctly with Jtag enabled !

happybenguy · Joined: 22 Apr 2005 Posts: 5

heh, yep, made sure it jtag was off first too(had that probem once though and it took me forever to troubleshoot Wink

)
see the thing is, is that it works the second way(8bit), but the first way it doesnt(4bit), and bascom default outputs to portb using its functions and 4bit mode. Im gonna keep messing with it tho. I'll let you know if i get it figured out. any more suggestions are well come.

DToolan · Posted: Sat Apr 23, 2005 1:04 am Post subject:

If your chip had an address / data bus (for connecting external memory) then you could "CONFIG LCDMODE = BUS". Afterward (with a few other config statements), the LCD commands would be as simple as usual (CLS, etc.). Unfortunately, the M32 isn't one of those chips. The 8515, M64 or M128 are some examples of chips with the alternate XRAM interface.

jenalcom · Posted: Sat Apr 23, 2005 6:25 am Post subject:

It may sound silly but -- have you tried to output without using the do..loop or using a longer wait time?

It may be that the CLS command is taking a long time on that display and you are therefore refreshing too quickly.

Just an idea

Alan

happybenguy · Joined: 22 Apr 2005 Posts: 5

well, i have tried to do it with just outputing one word then ending the program, but it had the same result. I do however have a 8515 laying around, so i am goin to try to figure out how to hook that up, but the way you make it sound is that i dont actually need the external ram, i just treat the lcd as the external ram, is that correct? well anyhow, im gonna try to play around with the 8515 tommarow and see what i can discover. Ill let you guys know what i find out.

DToolan · Posted: Sat Apr 23, 2005 7:16 pm Post subject:

No, you won't need any XRAM connected. Look in the HTML help file under "Adding XRAM". There is a diagram there showing what pins to connect to the LCD. The initialization code should be something like this...

ATIU · Joined: 15 Oct 2004 Posts: 534

You should look at the datasheet of your LCD on how to hook up the contrast bias voltage. Some requires negative bias while most will work with Vcc and Gnd. A pot, one connected to Vcc (+5v) and Gnd, while the center of the pot goes to the bias pin. My experience is that bias voltage is just about 0.5V, so connecting this to gnd will not work, or just darken the whole LCD. If connected a pot, then the other end should be connect to Vcc.