View Full Version : Experimenter card

07-15-2009, 08:12 PM
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 (http://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 :)

07-16-2009, 09:45 AM
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:



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.

Catalina - a FREE C compiler for the Propeller - see Catalina (http://forums.parallax.com/showthread.php?p=795326)

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

07-16-2009, 08:24 PM
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.

Composite NTSC sprite driver: Forum (http://forums.parallax.com/showthread.php?p=800114)
NTSC & PAL driver templates: Forum (http://forums.parallax.com/showthread.php?p=803904)
OnePinTVText driver: ObEx (http://obex.parallax.com/objects/480/) Forum (http://forums.parallax.com/showthread.php?p=822453)

07-17-2009, 11:52 PM
I think I've got an idea, I found a driver for 4 - 5x7 led matrix [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?