LCD interfacing?

[evandude]

anyone have experience with LCD's using the HD66702 controller?
I'm trying to get one working, and having a little trouble.
it comes on, first line is all black, nothing on the second line. just wondering if anyone had a similar experience and could give me some tips.

thanks

 

[Nigel Goodwin]

anyone have experience with LCD's using the HD66702 controller?
I'm trying to get one working, and having a little trouble.
it comes on, first line is all black, nothing on the second line. just wondering if anyone had a similar experience and could give me some tips.

They come on like that if you just put power on them, so it's probably not being controlled correctly. You don't mention what you are using to control it.

 

[evandude]

i'm using a PIC... i've set everything up on the PIC to do exactly what it says in the manual for the LCD, but it doesnt' appear to respond to any of the commands. gah. oh well... I guess i'll screw with it some more later. i've been messing with individual things, making sure everything fits the protocol in the manual... it would be helpful if i could just get some sign of life from it... maybe i'll have better luck tomorrow.

 

[Nigel Goodwin]

i'm using a PIC... i've set everything up on the PIC to do exactly what it says in the manual for the LCD, but it doesnt' appear to respond to any of the commands. gah. oh well... I guess i'll screw with it some more later. i've been messing with individual things, making sure everything fits the protocol in the manual... it would be helpful if i could just get some sign of life from it... maybe i'll have better luck tomorrow.

It took me a long time to get an LCD to work, loads of example code I tried just didn't seem to work. Eventually I used bit and pieces from all over the place, plus parts of my own and ended up with reliable, reproducable, LCD routines.

You can see the LCD routines as part of my PIC tutorials at http://www.winpicprog.co.uk, but my web forwarding appears to be down at the moment, so try the actual host site at **broken link removed**.

I've had good reports from lots of people over these routines, and I use them all the time.

 

[StupidDum]

i'm using a PIC... i've set everything up on the PIC to do exactly what it says in the manual for the LCD, but it doesnt' appear to respond to any of the commands. gah. oh well... I guess i'll screw with it some more later. i've been messing with individual things, making sure everything fits the protocol in the manual... it would be helpful if i could just get some sign of life from it... maybe i'll have better luck tomorrow.

LCD is not tough. After ensuring all the pin connections are correct, then just follow the steps to send command/data to LCD. If it doesnt work, try to add some delay in between data transfer, 20us should be sufficient.

 

[evandude]

yeah, well, that's what I have been doing. I've looked over the manual several times and can't see anything that i'm not doing exactly the way the manual says to... and i've got delays all over the place just in case.

 

[evandude]

alright, I've got it giving me a blinking cursor and both lines now. thanks for the help guys, the links gave me some assistance.

 

[k7michal]

what was the Key ingrediant? I too am working with LCD's and have been having the problem you describe.

 

[Exo]

Take a look here:
http://home.iae.nl/users/pouweha/lcd/lcd.shtml

You need to setup the lcd first. Telling it you want to use 4 bit or 8 bit interface, charachter size,...

 

[evandude]

i had a few things messed up... like one of my supposed output pins was set up as an input... and when i did finally get the LCD responding, all the characters were wrong... turns out that in the PIC i was using, the internal clock was off, so the USART was reading the serial data completely wrong... but then again that had nothing to do with the LCD.

just stick to the manual. check all your outputs, check your timing delay routines, etc... that's all that turned out to be wrong with my setup.
oh, and in case anyone's wondering, the HD66702 controller seems to use exactly the same setup procedure and commands as the MUCH more popular HD44780... i followed a guide for the HD44780, mostly because it was much easier to read than the manual for the controller that i have, due to it being written in very badly translated english... and everything worked out alright.