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Green rectangular circuit board with sixteen LED pads and keypad contacts in a four-by-four grid

Adafruit

Adafruit Trellis Monochrome Driver PCB for 4x4 Keypad & 3mm LEDs engineering development tool

SKU CH-WR1M-AQ3Y8

I2C driver board for a 4×4 keypad and 3mm LEDs, tiles up to eight units for 128 keys on one bus

  • Product typePrototyping Products
  • I2C bus controls 16 LEDs per tile
  • Tile up to 8 boards for 128 keys
  • Matches Adafruit 4x4 elastomer keypad
  • On-board sequencer reads keys and drives LEDs
  • Requires Arduino or similar microcontroller to operate

Adafruit Trellis Monochrome Driver PCB

This bare driver PCB is designed for the Adafruit 4x4 elastomer keypad. It provides the I2C-controlled sequencer and reader circuitry for 16 keys and 16 matching 3mm LED positions. The board contains no microcontroller, so an external Arduino or similar device is required to drive it. Engineers use it to add a backlit keypad interface to custom prototypes.

Suits embedded developers building custom keypads

Makers who need a ready-to-use keypad with integrated lighting should look elsewhere, as this PCB ships without any LEDs or elastomer buttons. Projects that cannot accommodate an external microcontroller for I2C communication will not be able to operate this board. Builders requiring more than 128 total keys must choose a different architecture.

Single I2C bus supports up to eight tiled boards

Up to eight driver PCBs can share one I2C bus, allowing a maximum matrix of 4x32 or 16x8 for 128 combined buttons and LEDs. Each tile handles its own 4x4 scanning and LED driving independently. This chaining capability is the key specification that determines whether the board fits the project's scale.

How it compares

Measured against everything we stock in Engineering Workstations & Dev Kits, at today’s prices. Recalculated every night.

Price $13.99
Pricier than about 60% of the 170 comparable items (median $11.49).

Specifications

Product
Product typePrototyping Products

Questions about this item

What microcontroller do I need to drive this Trellis PCB?

An Arduino or similar microcontroller is required to read keypresses and command the on-board LED sequencer over I2C.

Can I chain this board with older Trellis tiles I already own?

Up to 8 PCBs can share one I2C bus, giving 128 buttons and LEDs in a 4x32 or 16x8 layout.

How do I confirm the I2C sequencer is alive after wiring?

Scan the bus for the tile's address, then send a command to light each of the 16 LEDs in turn.

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