Your LED matrix display needs 12 or 13 digital pins, and only specific combinations will work.  If this much custom wiring worries you, choose the Feather M4 Express with an RGB Matrix Featherwing Kit, because just by connecting the headers you get everything in the right place!

If you hold a ribbon cable flat — no folds — and with both connectors facing you, keys pointed the same direction — there’s is a 1:1 correlation between the pins. The top-right pin on one plug links to the top-right on the other plug, and so forth. This holds true even if the cable has a doubled-over strain relief. As long as the keys point the same way and the plugs face the same way, pins are in the same positions at both ends.

Either end of the ribbon cable can be plugged into the matrix INPUT socket.

The free end of the ribbon can point toward the center of the matrix, or hang off the side…the pinout is still the same. Notice below the direction of the “key” doesn’t change.

A dual-row header gets installed on the prototyping area, similar to the connector on the matrix. Just like the ribbon cable lying flat, as long as these two headers are aligned the same way, they’ll match pin-for-pin.

Wires are then soldered from the header to specific microcontroller pins. Try to keep wire lengths reasonably short to avoid signal interference.

Using color-coded wires helps a lot! If you don’t have colored wires, that’s okay, just pay close attention where everything goes. Our goal is a proto shield something like this (but this is just an example; refer to the following pages for specific information for your board):

You can also use a plain 2x8-pin male header, or two 1x8 sections installed side-by-side (as in the photo above). Since there’s no alignment key with this setup, you might want to indicate it with some tape or a permanent marker.

Depending on the make and model of proto shield, some pins are designed to connect in short rows. Others don’t. For the latter, strip a little extra insulation and bend the wire to wrap around the leg of the socket from behind, then solder.

Connect Ground Wires

32x32 and 64x32 matrices require three ground connections. 32x16 matrices have four.


Most proto shields have tons of grounding points, so you shouldn’t have trouble finding places to connect these.

Upper RGB Data

Pins R1, G1 and B1 (labeled R0, B0 and G0 on some matrices) deliver data to the top half of the display.


Lower RGB Data

Pins R2, G2 and B2 (labeled R1, G1 and B1 on some matrices) deliver data to the bottom half of the display. 

Row Select Lines

Pins A, B, C and D select which two rows of the display are currently lit. (32x16 matrices don’t have a “D” pin — it’s connected to ground instead.)

LAT Wire

The LAT (latch) signal marks the end of a row of data.

OE Wire

OE (output enable) switches the LEDs off when transitioning from one row to the next.

CLK Wire

Last one!

The CLK (clock) signal marks the arrival of each bit of data.

Want to use a breadboard?  We've got you covered too.  With the Breakout Helper, the 16-pin header can straddle that big gap in the middle.

IDC Breakout Helper - 2x8 (16 pin)

This 2x8 (16 pin - 0.1" spaced) IDC Breadboard Helper is great in conjunction with any 16-pin IDC...
This guide was first published on Apr 20, 2020. It was last updated on Apr 20, 2020.
This page (Connecting Using a Proto Shield) was last updated on Sep 18, 2020.