Here’s a wiring schematic for the Raspberry Pi version. Refer back to this when getting to later steps:

Color-coded by function:

Red

+5V

Black

Ground

Blue

I2C SDA

Yellow

I2C SCL

Notice there are two groups of four matrices each. Each group gets wired to a different I2C bus. Specific pin numbers will be discussed later.

And here’s a similar diagram for Pico RP2040:

Build Steps

Prep Wires

Silicone female-to-female jumper wires will be used to link the matrices to header pins on the Raspberry Pi or Pico.

5 each of four colors are sufficient to build two sets of wiring harnesses. Cut these in half to produce 40 half-wires total, and strip about 1 cm of insulation from all the cut wire ends.

Twist four same-color wires together facing the same way, then twist one more wire from the other direction to produce a four-way splitter cable. Solder where these wires all meet, then cover the exposed solder joint with heat-shrink tubing.

Repeat the process above to produce eight such 4-way splitters in total, two each for power, ground, I2C data and clock. You can optionally use a bit more heat-shrink to tidy up the wire bundles.

Connect Cases

Align the case parts and use four M2.5x12mm screws to fasten together. 

Attach Frames

Use M2.5x8mm screws to attach the LED frames to the stand-offs inside the case.

Solder Driver 

Solder the longer end of the header pins towards the back of the driver board. The short side of the header pins face the LEDs and the acrylic sheets.

Solder Address Pads

Each matrix controller within a group of four must be assigned a unique I2C address, settable with solder bridges on the back. The first matrix can be left alone, using the default address of 0x74. The other three should get a single solder bridge, setting them to address 0x75, 0x76 and 0x77, respectively. Repeat for both sets of four.

Assembling the matrix-and-driver sandwich is explained in greater detail in this guide.

Solder Connection headers

Solder four header pins to each matrix. Solder the shorter pins to the driver board. The longer pins face away from the driver board and connect to the female jumper wires.

EXPERT TIP: experienced builders will always connect all wiring outside the case first, then skip ahead to the software setup. Once everything is tested and known working, disconnect and re-assemble in the case as we’ll show next. This adds extra steps but is SO MUCH EASIER to troubleshoot than after everything’s enclosed!

Attach Charlie LED Matrices 

Position each matrix in the order shown in the schematic at top, and with the four pin header connection towards the bottom. Leftmost matrix as seen from the front will be 0x74. From the back, these will be in the opposite order.

Attach Acrylic

The Black LED Acrylic slides over the matrices.

Plug in Jumpers

Connect each jumper to the corresponding header pin on each matrix, and to the Pi or Pico as shown in the corresponding wiring diagram at the top of this page.

Attach Vents

The back vents press fit into the walls around each cube.

Mount Pi or Pico

 

Use M3x6mm long screws to mount Raspberry Pi computer. The USB port align the cutout on the bottom case.

The Raspberry Pico mounts what an addition frame over the stand-offs on the bottom case.

 

Attach Bottom Case

Use four M2.5x8mm screws to attach the bottom case. 

As mentioned on the Overview page, the USB right-angle connector will block the HDMI ports. This is fine for “headless” use, as with an OctoPrint server. If you require HDMI out, you’ll need to improvise with a different USB adapter or cable.

This guide was first published on Apr 19, 2022. It was last updated on 2022-04-19 18:34:16 -0400.

This page (Assemble) was last updated on May 15, 2022.

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