Experimenter card

FredBlais

Hey, I would like to put a 5x7 led matrix like this one : cgi.ebay.ca/5x7-dot-matrix-Red-LED-Display_W0QQitemZ220350280990QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item334de6751e&_trksid=p3286.m20.l1116
Someone has an idea how to drive it properly with the less io possible? Hope that it can fit in there [noparse]:)[/noparse]

RossH

Hi FredBlais,

With this type of display you have to multiplex the outputs, since not all the LEDs can be individually addressed at the same time.

I think you could do it in 8 I/O pins plus one ground pin if you have the appropriate "helper" chip. Here is a project that describes something similar:

http://www.best-microcontroller-projects.com/led-dot-matrix-display.html

Ross.

EDIT: Actually, on second thoughts I don't think you'd need any "helper" chips at all - I think the Prop should be able to do all the multiplexing fast enough to fool the eye.

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Catalina - a FREE C compiler for the Propeller - see Catalina

Post Edited (RossH) : 7/16/2009 5:58:27 AM GMT

ericball

It all depends on the number of propeller pins you want to use. The simple way would be to connect the 12 pins directly to the Propeller (well, through some series resistors). You could probably get it down to 2 pins with some external chips - two shifters to select the row & column (one pin to reset the shifters), and one pin to control the selected LED.

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FredBlais

I think I've got an idea, I found a driver for 4 - 5x7 led matrix [noparse][[/noparse]MAX6953] that works with I2C, so I could drive two bi-color display.
I don't think I can wire that on the experimenter card (it's just too big) so maybe I would have to make my own board,
but I never did any board layout before :S
Anyone already made an expansion card for the hydra?

http://www.lc-led.com/View/itemNumber/287
http://datasheets.maxim-ic.com/en/ds/MAX6953.pdf