In simplified schematic form, here’s what we’re aiming for:

There’s just four connections between the Feather board and each I2C display backpack:

Feather HUZZAH Board

4-digit 7-Segment I2C Backpack




SDA (4)


SCL (5)


For a single-display clock, it’s super simple, just four wires between the boards. With multiple displays, you can either try a multi-way splice, or it’s usually easier and more robust to use a piece of a Perma-Proto board to distribute power and signals to multiple points (I’ll show an example of this on the “Enclosure” page).

The 7-segment display/backpacks require some soldering. It is vitally important that the display be correctly oriented atop the backpack PCB! Use the decimal point markings (or the colons (:) on the 1.2" displays) as an indicator. The IC chip should be visible on the back of the assembly, NOT covered by the display.

If you get the orientation wrong, the display will not work. You’ll need to desolder all of the pins and re-assemble it correctly.

With multiple displays, each must be assigned a unique “address” using the A0, A1 and A2 solder jumper pads on the back:

The default, with no solder pads bridged, is address 0x70. Bridging the A0 pads will add 1 to the address. Bridging A1 adds 2, and A2 adds 4. This allows a maximum of 8 distinct combinations.

Take note of what address you’ve assigned each display — you’ll need this information later to configure the software.

After soldering the display(s) to the backpack(s), you can trim the wires so they don’t poke out the back as much.

You don’t have to wire up the displays to the Feather board yet (I’ll do that on the “Enclosure” page)…lets get the software side set up next, confirm we can access the network before snaking lots of delicate wires around inside a case.

This guide was first published on Apr 03, 2016. It was last updated on Mar 30, 2016.

This page (Circuit) was last updated on Mar 30, 2016.

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