3

Note: I have read Controlling many LEDs with few GPIO pins, but I can't buy additional parts (Degree project)

The end result is to make a noughts and crosses grid with 2 LEDs per grid cell. This means I will need to be able to light up 18 LEDs individually. Therefore wiring two LEDs in parallel in each cell means I can light each LED depending on the direction of voltage bias applied.

This means I will need a total of 18 RPi connections, however there are only 17 GPIO pins.

I have looked at Charlie- and Multi-plexing and a couple of other LED matrices, but none of these seem to be suitable.

Any ideas?

Community
  • 1
Pingk
  • 131
  • 2
  • 5

4 Answers4

2

Here is a similar question regarding controlling multiple LEDs with a Raspberry Pi with limited GPIO. As @Fred mentioned there are additional headers, but using an I/O extension such as a multiplexer would further expand your possibilities.

Community
  • 1
Mike Naylor
  • 314
  • 1
  • 6
0

If you have a Revision 2 Pi, there's the P5 header, which adds another 4 GPIO pins. This could be an easy way around it.

Fred
  • 4,592
  • 19
  • 29
0

if you have a skilled solderer, you could desolder the ok-led from the raspi's face, and wire one to that, since thats a controllable led

ExploWare
  • 350
  • 1
  • 10
0

You can use this circuit or an equivalent one.

It's serial based so it only uses 5 pins (VCC, Ground, SERIAL, SERIALCLK, WRITECLK).

If you use only one board you can control 32 outputs

Multiple boards multiplies the possible outputs, but you need to send more bytes and latency will be higher.

Ghanima
  • 15,958
  • 17
  • 65
  • 125
nucandrei
  • 121
  • 5