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led matrix

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bloody-orc

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Hi there.

i have a problem. i'm trying to control 15x15 bipolar-led matrix. leds have 3 leads (one common and other different). 1 can only bare 2 ports for that from my uprocessor. what schematic should i make inbeteween them?

i was thinking of somekind of counter thingis but cant make up a good schematic or this saddly can anyone please help me...

best regards
Rain

PS: (sry for doublepost)
 
control 450 LED junctions, with only 2 io lines, my goodness that's ambitious

Maxim has an i2c 2-wire IO expander (LED drivers), MAX6956, which offers 20 tri-state latches ... so three of those would work ... one for your anode rows, and two for the bi-color cathode columns (or whatever), you can use up to 16 of them on a single i2c bus.

alternately, you could look at a 74HC595 serial load shift register... but its a 3 wire device, perhaps you have a control line that you can dual-purpose, using steering diodes?
 
who sed anything about 2 IO lines. i sed 2 ports (that is 16 IO lines). maybe some clock outputs at some point and some counters in the middle... i just cant figure it out myself...

IO expanders cost too much for me so those i cant use saddly :(
 
oooo, okay ... two 8 bit ports, not two lines .. gotcha

well then, I recommend two 'lines' of 74HC595 latches for your columns, and drive the rows with a multiplexer or straight off the uP

theres a lot of talk about the 595 already on the forum, including schematics ... basically you hook up 3 lines from your uP; Clock, Latch and Serial Data ... then you bitbang out your data, toggle the latch and presto, the latches display a parallel representation of the data you clocked in serially.

you'll need four 595's, connected as two sixteen bit latches, then can share common clock and serial data lines, but give each 16 bit register its own latch line, and maybe each its own clear line (they have lots of options, check the DS). there is 32 outputs to drive your 30 columns (2 sets of 15 right?)

for the rows, use a multiplexer (takes 3 control lines) or direct-drive them from the uP ... depending on the power involved (whats the rating on the array?), you'll probably need power transistors to drive the rows... assuming 10ma per led junction, 30 junctions per row, thats 300mA, well beyond what a normal uP or uC can deliver.
 
yes, very nice. this chip seems to do the job. now to figure out how da hell do i use one ;) the datahseet i found was so "shitty".
 
the datasheets don't give any programming examples if thats what you mean.

I can share some Picbasic code if you're interested

I used a 24 bit register (three 595's) here to control eight RGB leds:

https://projects.dimension-x.net/archives/51

not exactly the same as your application, but you could think of it as one row in an array.
 
thanks for help. i have found some DS's for other chips that have examples of how to interwace the chip to a controller and some bitrows of what should go in the data input etc. but well i hope i get some info from your programs (lucy i speak basic...)


Cant fint the soft nor schematick... could you send them on my email at
 
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