As mentioned on the “Jumper” page: 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 proto shield, 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; unlike the jumper wire method from the prior page, mirroring doesn’t happen.
Wires are then soldered from the header to specific Arduino pins on the proto shield. 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:
It’s not necessary to install all the buttons and lights on the proto shield if you don’t want — just the basic header pins are sufficient.
For Arduino Uno, using an Adafruit proto shield: if using a shrouded socket (like on the back of the matrix — with the notch so a ribbon cable only fits one way) you’ll need to place this near the “Reset” end of the shield. The plastic shroud obscures a lot of pins. Others’ proto shields may be laid out different…look around for a good location before committing to solder.
For Arduino Mega with our corresponding proto shield: a shrouded socket fits best near the middle of the shield.
Otherwise, you can 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.
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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. |
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For 32x32 and 64x32 matrices, LAT connects to Arduino pin 10.
For a 32x16 matrix, use Arduino pin A3.
This is the same for Arduino Uno or Mega.
The LAT (latch) signal marks the end of a row of data. |
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CLK connects to pin 8 on an Arduino Uno, or pin 11 on an Arduino Mega.
The CLK (clock) signal marks the arrival of each bit of data. |
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OE connects to Arduino pin 9. This is the same for both the Arduino Uno and Mega.
OE (output enable) switches the LEDs off when transitioning from one row to the next. |
Here’s that photo again of a completed shield. You can tell this is for a 32x16 matrix, because there are four ground connections (one of the long vertical strips is a ground bus — see the tiny jumpers there?).
The ribbon cable to the matrix would plug into this with the key facing left.
The colors don’t quite match the examples above, but are close. G1 and G2 are yellow wires. LAT is the purple wire.
