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Keith W.
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Joined: 09/10/2011
Location: Australia
Posts: 118

Posted: 10:53am 09 Oct 2011

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Hi Maximite Forum,

Long a follower of the Forum I have gained knowledge and enjoyed Forum discussions. I now have something to contribute that may be of interest to others.

I was tempted to buy a Displaytech 64128A 128 by 64 Graphic LCD Display from Rockby Electronics at the price of $7 each. I am also interested in I2C for a larger project. To start I have used a Picaxe 28X2 to drive the display to preserve Maximite pins, using I2C for communications with the Picaxe. I required 14 pins to drive the display. Believing that a Maximite graphic was required I scanned the Enclosure Label from page 90 of the April �Silicon Chip� article, some pixel editing and then I created a pixel ascii hex text file. A little Maximite program converts this SD card text file to a binary file. Graphic and text and position information may then be transferred from the Maximite SD card to the Picaxe. A limited small character font (capitals and digits and 5 other letters) is squeezed into the Picaxe-28X2 256 byte EEProm. Display commands are: - Clear screen, Position to X-Y, Load Graphic Pixels and Display Ascii text. The Picaxe and display is limiting update speed. The MMBASIC code employs delays between messages to the Picaxe though some I2C messages themselves contain 250+ bytes. The LCD screen has separately enabled driver chips for the left and right halves of the display. This complicates the Picaxe code to automatically switch halves. I was assisted in my project by another displaying test on a graphic LCD found on the web.

I wish to urge Geoff Graham to present a Maximite Logo Graphic on screen at start up.

What do you think?

Keith W.

crackerjack

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Joined: 11/07/2011
Location: Australia
Posts: 164

Posted: 10:58am 09 Oct 2011

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Hi Keith - very cool - my post 1 minute ahead of yours is on a very similar topic - that of displaying a splash image. I have a small program that loads a BMP file from the SD card and displays it on the VGA screen. There is a lot of common thinking (though different approaches) on the same sort of topic. Interesting...

Lance.

Keith W.
Senior Member

Joined: 09/10/2011
Location: Australia
Posts: 118

Posted: 11:07am 09 Oct 2011

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Hi Lance,

I was looking for a quick answer. Interested in driving the LCD. The original graphic was anti aliased and my scan was jaggy although I ended up with a .bmp after editing. I then cheated and hand coded the graphic, only 512 pixels.

Keith.

MOBI
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Joined: 02/12/2012
Location: Australia
Posts: 819

Posted: 09:07pm 14 Mar 2014

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Hi Keith,

I was browsing through i2c topics and found your post. I thought it might be worth revisiting for the uMite.

Some years ago, I was given a 64x128 LCD without driver so I wrote one. I just wondered how it compared with yours with respect to i2c protocol etc.

David M.

Keith W.
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Joined: 09/10/2011
Location: Australia
Posts: 118

Posted: 12:22am 15 Mar 2014

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Hi David,

Now you are taking me back so far that I cannot yet find the Maximite code.

I have zipped up the Picaxe code and the circuit of the picaxe driver card behind the display. The circuit is in two parts because it is a screen grab from Diptrace. Perhaps it is only in the free version but you cannot seem to save the schematic in anything but the Diptrace format.

The picaxe acts to interpret the I2C messages and drive the screen. I hope that you can work it out. I will continue to look for the Maximite code that sends some test messages and the graphic data file at least. I did not go further with this project; something else must have been more interesting. The particular picaxe had just enough rom memory to squeeze in a simple capital font in compacted data format c/w numerals. The font is from the old BBC computer and designed to look OK with minimal size. The Micromite can manage must more than that. Rockby Electronics still have 128 * 64 LCD displays at ever decreasing prices.

2014-03-15_102103_Picaxe_128_64_.zip

Keith W.

MOBI
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Joined: 02/12/2012
Location: Australia
Posts: 819

Posted: 12:49am 15 Mar 2014

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Hi Keith,

So you actually built the LCD driver using a PICaxe? How did it go for speed?

The one I wrote used a PIC16F88. The info you have given me will allow me to compare my i2c data format with yours. Do you think the 64x128 has a future with the uMite?

Can't say as I've ever used a picaxe as an i2c slave before. It is too easy to drop a specific function into a pic slave template.

regards

David M.

MicroBlocks

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Joined: 12/05/2012
Location: Thailand
Posts: 2209

Posted: 01:00am 15 Mar 2014

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@Keith,

I use a PDF printer to 'print' schematics from Diptrace.
You can depending on which pdf 'printer' you have also print to a picture file as output.

Microblocks. Build with logic.

Keith W.
Senior Member

Joined: 09/10/2011
Location: Australia
Posts: 118

Posted: 01:32am 15 Mar 2014

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David it was slow, would not recomend it for graphics but may find a place in some application. I have not found one yet, still sitting in a box. From memory it was the display that limited the speed, taking ages to swallow the data and the write handshaking did not work correctly. The picaxe did not set the world on fire.
Have used many othe character LCDs with less trouble.

Perhaps if these display were OK (useable) they would not be $7 each.

TZA Thank you, I had not thought of that solution. I will find a PDF printer. Makes sense.

Keith W. Edited by Keith W. 2014-03-16

WhiteWizzard
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Joined: 05/04/2013
Location: United Kingdom
Posts: 2927

Posted: 02:17am 15 Mar 2014

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Has anyone else used an EA-DOGXL160 display? These are 160x104 and have a choice of interface on the one PCB.

If so what was the interface you selected, and was it fast enough for basic graphical displays? Note, I am not trying too achieve smooth full-screen animation!

I really like the modular approach in terms of their range of back-light choice. The screens draw minimal current, and I think they are reasonably priced for the consistent quality they give.

However, if there are alternative displays that meet these requirements that you have personally used before then please pass on any info for me to look at!

Thanks . . .

MOBI
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Joined: 02/12/2012
Location: Australia
Posts: 819

Posted: 12:38pm 15 Mar 2014

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Quote it was slow, would not recomend it for graphics but may find a place in some application

I think my version was quite fast but like you, I'll have to dig it out of the junk box and try it. It was a serial set up but with a bit of pin manipulation in firmware I reckon it can be made i2c. I also did a 240x128 lcd in serial mode.

I want to breadboard up a uMite with keypad and LCD (20x4) using uMite direct, not i2c and see if it will run my software then I'll have a go at the 64x128.

Some years ago, I came across a picaxe driver for a mono Nokia display. As you say, it was s l o w, particularly with clear screen, so I did up a pic16F628 version which was a very significant improvement. Clear screen as good as instantaneous.

David M.

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