Need Help with 8x8 LED unit (not pimoroni product)


#1

Hey guys I have this 8x8 LED matrix unit.

Its been laying in my todo box forever but I have no idea how this works with the raspberry pi.

Does anyone have some ideas?


#2

This is a good introduction to how these kinds of displays are configured: http://www.appelsiini.net/2011/how-does-led-matrix-work

You’ll need to do some probing (or find the datasheet) to determine the exact pin out though!


#3

Looks like you’ll need to dig up a datasheet as a first port of call.

It’s basically a bunch of LEDs that share common anode and cathode pins. You can light each one in turn by applying a voltage across the two pins that correspond to it.

A quick Google of the number on the side results in this page: http://binusmt.in/ld-1088bs-pin-details/

I’m not sure where pin 1 is on your device, but you should locate it, and connect a 3.3v supply through a large resistor ( 600ohm to 1k ) to be on the safe side. Then locate what you think might be pin 3 and connect it to ground. An LED should light up!

You can use this method to trial-and-error your way through finding all the anodes/cathodes of the LEDs if the graphic in that link is wrong.

As for connecting it to the Pi, you’d usually use an LED driver chip to do the heavy lifting- it’d talk i2c and handle driving the LEDs. From the Pi you’d only theoretically be able to turn on about 20 of the 64 LEDs at any one time before you blew the budget ( based on an arbitrary estimate of 3mA per LED ).


#4

Throwing in my very lazy alcohol addled and most likely useless 2 cents here: I got one of these because they were cheap, but didn’t have the time to figure it out so…err…I think it’s in my component box.
That was partially because the wiring for mine was very very weird (think rats nest). I think adafruit do a backpack if you want to cheat, tho it’s not for 8x8 - http://www.adafruit.com/product/1427 (not sure pimoroni have it?) might be a starting point for your own design though.


#5

I’ve just cobbled together some python code to drive an 8x8 direct from the B+ GPIO (should work with B too if you use all available GPIOs).

http://pastebin.com/nCaZgVAf

It’s not overly bright but works. Charlotte’s suggestion is how I have worked with these in the past. http://fortoffee.org.uk/2013/12/8x8-snake/ much easier!


#6

@gadgetoid would you be able to use this one http://shop.pimoroni.com/products/1-2-8x8-square-led-matrix as you suggest herein.

Bonus question 1: how many LED would you be able to light at once using a model A+ and 2A PSU?
Bonus question 2: would it fit the breadboard on an Explorer (including resistors, which I guess would be required?)