Has anyone Used the ST2225A chip with the SX?

jmevans

I recently purchased one of these LED display units for $1.00
http://www.allelectronics.com/cgi-bin/item/DSY-1/345/MULTIFUNCTION_LED_DISPLAY_MODULE_.html

I see that David Cook at Robot Room has used them with a Atmel AVR ATtiny
http://www.robotroom.com/MultiSegmentLEDDisplay.html

From looking at the data sheets for the ST2225 that is used
http://www.siti.com.tw/product/spec/LED/ST2225A.pdf
I see that I need to use a clock signal and send 36 bits at a time.

I would like to experiment with using this display with the SX,
could any one share a little sorce code in SXB that would work
with this unit?

Thanks
Mark

T&E Engineer

I have not been able to find anything on the Parallax forums on the ST2225A (and almost nothing on Google too). It looks like a neat chip. Since it appears to be an SPI type chip, you might want to read about my posting with another similar SPI chip called the LC7932M found on an AD-501-B 16x16 LED matrix board from www.Futurlec.com .

I went through the same struggles in learning how to interface to an SPI LED type chip. You will need to spend some time reading and re-reading through the ST2225A datasheet and see how it compares.

Here is a link to the work I did on the AD-501-B board (w/ LC7932M chips) for the SX-28. There is also a link within that link for original work done on a BS2 chip by Parallax.

http://forums.parallax.com/showthread.php?p=658966

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jmevans

Any other Examples of how to send 36 bits with a clock signal for each bit?

JonnyMac

I'm on my way over to All Electronics -- I'll pick one up and write a demo for it; when I can (things are a bit busy lately).

jmevans

JonnyMac,

Were you able to pick one of those up?

They seem like a really good deal. I can get mine to light up using shiftout but I can't seem to get any legible char.'s

Mark

JonnyMac

I had the same experience; I am under the impression that you have to do the multiplexing manually; that means the communications via SHIFTOUT is going to need to be constant and, therefore, should be moved to an interrupt.

Zoot

That is one cool display for $1.00.

Indeed, according to Mr. Cook's article, the display has the driver, but does not multiplex; the host is responsible for that:

Somebody said...
The microcontroller must redraw each portion of the display over and over very quickly (refresh) to make it seem that the entire display is lit at the same time.

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jmevans

Any Luck Yet?

Vern Graner

jmevans said...
Any Luck Yet?

This looks promising:

http://www.serialwombat.com/sdk/pin_mode_phoneled.htm

I know it is an example using something called a "wombat" but maybe the source code included on the page would be a good place to start reverse engineering code for the SX?

Vern

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jmevans

Great find, It looks promising.