Trellis is an open source backlight keypad driver system. It is easy to use, works with any 3mm LEDs and eight tiles can be tiled together on a shared I2C bus.
The Trellis PCB is specially made to match the Adafruit 4x4 elastomer keypad.
Each Trellis PCB has 4x4 pads and 4x4 matching spots for 3mm LEDs. The
circuitry on-board handles the background key-presses and LED lighting
for the 4x4 tile. However, it does not have any microcontroller or other
'brains' - an Arduino (or similar microcontroller) is required to
control the Trellis to read the keypress data and let it know when to
light up LEDs as desired.
Each tile has an I2C-controlled LED sequencer and keypad reader already
on it. The chip can control all 16 LEDs individually, turning them on or
off. It cannot do grayscale or dimming. The same chip also reads any
keypresses made with the rubber keypad. The connections are 'diode
multiplexed' so you do not have to worry about "ghosting" when pressing
multiple keys, each key is uniquely addressed.
The tiles have 3 address jumpers. You can tile up to 8 PCBs together
(for a total of 4x32 or 16x8=128 buttons/leds) on a single I2C bus, as
long as each one has a unique address. All the tiles connect by the
edges with solder, and share the same power, ground, interrupt, and i2c
clock/data pins. So, you can easily set up to 128 LEDs and read up to
128 buttons using only 2 I2C wires! The tiles can be arranged in any
configuration they want as long as each tile is connected to another
with the 5 edge-fingers.
Each LED is multiplexed with a constant-current driver, so you can mix
and match any colors you like. You don't need it to be all blue, all
red, etc. Mix it up! Any 3mm LED can be used, although we find that
diffused LEDs with 250mcd+ brightness look best.
Last updated on 2013-12-06 at 09.56.22 PM