GLCD Found, is it worth buying?

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George Sephton

Senior Member
Hi,
Ive been looking at GLCDs for a while not finding many cheap ones but I found these on ebay and they are so cheap. Is it worth buying and will it interface with a PICAXE, second question Ive used Alhapnumeric displays with the hitatchi driver that uses less than 14 pins, do GLCDs work in the same way? and does this one?

George.
 
lbenson

lbenson

Senior Member
From the data sheet, a lot of pins to drive and a non-trivial command interface, but for 99 pence, why not try it--it's only your time ;-)
 
A

Andrew Cowan

Senior Member
For £3 (inc postage), I think it is a waste of time - if would be very hard to drive. However, if you fancy a challenge...

A
 
W

westaust55

Moderator
George,

Food for thought:

Others here have likely not used that gLCD so you may be on your own,

That gLCD has just under 4000 pixels whereas the gLCD from a Nokia 3310 mobile phone has just over 4000 pixels in 84 x 48 format and is a easy to connect. Eclectic has used one of those. Nokia 3310 gLCD's are relatively easy to find on eabay and elsewhere.

Alternatively if you can locate a Siemens A55, this gLCD has almost 6500 pixes in 101 x 64 format. Do a search and you will find a thread here where I used one for text and simple graphics.
 
G

George Sephton

Senior Member
Ok, I saw the HD66206 and the pins were a lot like the HD(Can't remember) used on alphanumeric display. I thought they would run in the same way.
 
B

BeanieBots

Moderator
The pins and how they connect will be very similar if not identical.
Even how to send for example the byte $0D will probably be the same, but then what?
Send 1 to most alphanumeric displays and they will initialise.
Then send "A" and the letter "A" will appear at wherever the cursor is.

You can't send "A" to a gLCD and expect a letter to magically appear somewhere. What size, and where? At best, you can turn on/off a pixel in a place of your choice. To draw a line, you will need to calculate the co-ordinates of each pixel on that line and then turn the required pixels on or off accordingly.

It can be done, it has been done but not with that particular display.
Follow the links given earlier, read the datasheet and you should be able to do the same. The only difference you are likely to encounter is with the actual commands and numbers you need to send to get the desired pixels to go on/off.
 
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George Sephton

Senior Member
Yeah I was expecting that but one could have a lot of fun designing the screen and people do bitmap to GLCD Software. The only other problem was that not much appears on google when searching for HD66206 and there arent any tutorials like there are for the other driver so I wouldnt know how to turn a pixel on and off. The datasheet doesnt appear to say how to either.
 
D

Dippy

Moderator
George,

Like BB says, it is not a simple matter of firing a character at the screen.

For example, for fonts, if the GLCD doesn't have a built-in character memory then you have to build characters in cells, for example 8x5 or 7x5 or whatever.
e.g. $7E,$11,$11,$11,$7E,$00, // 65 - A - 41
This can be sent to an area on the GLCD.
But, all of this means a lot of logic line switching to define the area or location where you are sending a block.
Larger fonts require more data points for a larger cell obviously.

As BB says, other switching can (after reading the Data Sheet) can put a spot/pixel on the screen at a co-ordinate specified by a previous command.
By sending bytes you can define x pixels in one hit to speed things up.
This is where you have to make all those control and data lines go on-off at the right time and in the right order !!
Do the maths an you can produce lines an circles.
Take it another level and you can plonk images on the screen.

And even if you did manage it, after a year or two, then it would be so slow compared to an interpeter firmware chip - where you could serially fire a character at the screen and get on with your own programming. A pukka chip is probably 50 to 100 times faster than you trying to do it on PICAXE.

Also, and I don't mean to poo-poo that wonderful institution of Ebay, but I have heard of some 'low-cost' (crap) GLCDs not working correctly with interpreter chips.

So, if you get one and it doesn't work then you ask yourself; is it the GLCD or is it my code? (Most likely the code of course, so sorry.)

Personally, I'd say forget it.

When you are a newbie it's best to start off with some things that work ;)
 
D

Dippy

Moderator
A PROPER GLCD Data Sheet will provide all the timing sequences in the form of descriptions and diagrams.
PROPER Data Sheets are usually at least 30 pages long -apart from ones with fewer pages ;)

It is unlikely that you will find a PICAXE tutorial. With all respect due, I'm sure you could eventually get something basic appearing on-screen but even medium speed will require PIC code.

And you will need EEPROM to store an image from your PC for display by your chosen processor.

George, close that Ebay page and look for something a bit more expensive :)
 
hippy

hippy

Ex-Staff (retired)
Software wise it isn't too bad to drive and if doubling up horizontal pixels an entire bitmap could be held in 256 bytes of Eeprom. Hardware wise, not so nice -

* 3V operation
* Negative Vlcd contrast voltage needed
* Not very large
* Effectively a two line display, each 7mm x 48mm with 1mm vertical gap
* Connections on 1mm pitch ( 18 wires )
* Needs 12 output lines to control it

I was tempted, but each awkwardness knocks its practical usefulness to me down, and no doubt why it's so cheap compared to other GLCD's. Probably a good buy if you have a suitable use for it, can handle the hardware, and wanted a few to get the total cost down, assuming it works as described.
 
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