Help with a LCD + Firmware Chip

#1
Right guys, This might be a dificult one to solve. I do my best to describe what I've got and what's going wrong.

So I've just bought a LCD Screen off ebay, cheap one from Hong Kong with a Back light. Here it is:

http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&rd=1&item=230156093498&ssPageName=STRK:MEWN:IT&ih=013

Since i wish to interface this with my Picaxe 28X microcontroller, i also purchased the serial firmware chip from microzed.com.au - Link - http://www.microzed.com.au/PDF/FRM010.pdf

So I've made my PCB, its all printed out and what not. Spent part of the day wireing it all up. All fine, checked it over etc and then turned the power on. Back light turned on and also some white boxes on the LCD screen (It's ment to display a welcome msg). I just can't work out what I have done wrong. It seems like its shorting out somewhere, but i cant find it.

So I've been looking at the data sheet and I dont understand part of it. On the "LCD module connetions" of the firmware manual and Vss, R/W d0, d1, d2 and d3 is connected to 0v and ALSO it states that these lines should be connected to Pin 5, which is infact 0v as well (easer to see on the manual). Is that a mistake??

Can any one suggest a solution that may help me out here? I understand that its far fetched but I really am stuck here.

Cheers
 

hippy

Technical Support
Staff member
#2
It's a HD44780 chipset device according to the eBay advert so it should work. Getting 'white blobs' is a good sign and suggests the display is powered-up, working, but hasn't been initialised properly. Check that D4-D7 are wired correctly and are not crossed over or to the wrong pins.

The LCD is configured as a write-only device so R/W can be tied to 0V. D0-D3 are not used in 4-bit / write-only mode, so <i>can </i> be connected directly to 0V although I would normally leave them not connected to anything, or to 0V via 1K.
 
#3
Hummmmm, Just checked over it, looks fine. Is their a chance that my potentiometer is faulty and causing the problem? Also, is the potentiometer polarized?
 
#6
With this type of display , I do not use
a variable potentiometer for the contrast
adjustment but a fixed resistor of 4.7 k
connected from the contrast pin to ground.
Since you have a 28X why not leave out the
firmware chip and connect directly to the
PICAXE in 4 bit mode.

Kym
 
#7
Humm ok, I will try that 4k7 resistor. Reason why I dont want to connect in 4 bit mode is because I'm running 4 relays, wireless tx/rx, and other various outputs.
 

hippy

Technical Support
Staff member
#8
<i>Reason why I dont want to connect in 4 bit mode is because I'm running 4 relays, wireless tx/rx, and other various outputs. </i>

There's some confusion here - The LCD connects to the FRM010 in 4-bit mode.

An option would be to temporarily run the LCD in 4-bit mode directly from a PICAXE to get it working and then move it to the FRM010 once the issues have been solved, but that could introduce more issues than it removes.
 

hippy

Technical Support
Staff member
#9
dxb1 : <i>So I've made my PCB, its all printed out and what not </i>

It is probably worthwhile posting a link to images of the PCB tracking and photographs of the assembled item if you have them( both sides ) so others can cast a fresh set of eyes over what you have.

Presumably the setup was not prototyped on strip-board or bread-board and this is the first attempt to get it working ?
 
#11
Right here we go.

This is a pic of the LCD screen.

http://imagecloset.com/view5/003d5522929a1fcd830a3e4dfbecabdb/DSC04471.JPG

And here is a pic of the PCB Board, its hard to edit this one, sorry.

http://imagecloset.com/view5/45eac452039db440f0998aabd34c56b3/DSC04470.JPG
 

hippy

Technical Support
Staff member
#12
Despite being labelled as HD44780 on eBay the datasheet shows it actually uses an S6A0069. This should be compatible but it may not be 100% compatible. I found a Spanish language site which had a user of that chipset reporting problems but no definitive answer there. A more extensive web search may turn up more.

If you have another LCD you know worked you can try using that driven from the FRM010 to see how it fares.
 
#14
Or, armed with datasheet, try to drive it direct from the 28X even if just to eliminate it from enquiries. The 28X has enough I/O to run it in 8-bit mode which will be a bit easier to follow and to write a simple test routine.
 
#15
Hi,
I have bought the 20x4 units (same make but from a uk supplier), off ebay and they work fine with both the firmware chip and direct from the picaxe in 4 bit mode (think it was hippy's site or the advanced interfacing manual that the code came from).If the 16x2 module has the same chipset the only slight difference from the one in the lcd manual was some of the character set were slightly different and included a small o (degrees)at hex address DF and an Omega sign at hex F4. The 20x4's I have seem so far to have been a great buy.
 
#16
you could try connecting an led from pin 17 of the serial firmware chip via a 680 ohm resistor to 0v, it should flicker if serial transmission is working, (as per data sheet).
Ive also put an led and resistor on the serial output pin of the picaxe to check picaxe output.
 
#17
Just a thought, when you said &quot;some of the white boxes light up&quot;, If the welcome messages etc are jumpered out all that is shown is half of each Character box (split diagonally) is that what you have?.
 
#18
BeanieBots - I cant wire it up in 4 or 8 bit mode since my PCB has been etched.

kevrus - I have the LED Connected already, pretty sure that it flickers. I can't check it since I need a new power supply.

ercotronic - Yeh that sound like what I got yesterday (can't show any pics yet). A series of boxes light on the screen and slowly fade away after about 3 secs. The box's seem to be &quot;cut&quot;, as in a row of pixels is cuting through them. (Hard to show with out pics I know) This is with the welcome msg enabled.

I should be able to get my power supply tomorrow some time and then post up some more pics.

Thanks for your help.
 
#19
If you find thats what you have then it sounds like you may have tied the jumper pins to the wrong rail if so I think you will also have to alter the baud rate in your code as this also will probably be wrong once you start communicating with the unit.
 
#21
Just had a quick look at the data sheet as a reminder and it says that the weak pullups &quot;should&quot; be enough to leave the pins unconnected but if everything else fails then tie them to the +ive rail with a 1k resistor just to be sure. I really dont think you are too far away from getting this display to work.
 
#23
Right, so this is a pic of what I'm getting on the LCD:

http://imagecloset.com/view5/22b20a1dd28ed79da7d3c5c56e8fc85f/30-08-07_1509.jpg

Im going to totaly rewire it, if that doesn't work I'll buy a new one.
 
#24
Right, so this is a pic of what I'm getting on the LCD:

http://imagecloset.com/view5/22b20a1dd28ed79da7d3c5c56e8fc85f/30-08-07_1509.jpg

Im going to totaly rewire it, if that doesn't work I'll buy a new one.
 
#25
That certainly does not look right to me!
before you do a rewire just double check that the soldering on the lcd pins etc is ok, it maybe the picture but the ones on the left look very close, also double check that the data pins etc are all where they should be it looks like you are extremly close to getting this up and running. What frequency oscillator is the firmware chip using?
 
#26
Yeh, not sure about the freq?? I checked it all over 10 times - still nothing - and now I'm just going to rewire it and see if that helps, making sure i do a better job than last time. Will let you know mabey later tonight.
Cheers
 
#27
Nop, still isnt working :(

I might try and claim this one as faulty, see if I can get a new one before this project is due.

Big thanks to everyone that tried to help me. :)
 

hippy

Technical Support
Staff member
#28
When all else fails, the LCD can be wired to bread-board and suitable pull-up / pull-down resistors can be added so you can clock initialisation and data into the LCD by hand, using switches or just by connecting the LCD input pins to 0V/+V.

You probably aren't interested in doing that at present, but it's always there as an option.
 
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