Connecting

As shown here, Trellis is just an LED/keypad controller. You still need an Arduino or similar to do the work of reading the keypad data and then signifying when to light LEDs.

Luckily, we wrote a library that handles all the hard work for you, making it all very easy!

Download the Trellis Arduino library from our github repository by clicking this shiny button
Rename the uncompressed folder Adafruit_Trellis. Check that the Adafruit_Trellis folder contains Adafruit_Trellis.cpp and Adafruit_Trellis.h, and an examples folder

Place the Adafruit_Trellis library folder your sketchbookfolder/libraries/ folder. You may need to create the libraries subfolder if its your first library. Restart the IDE. You can figure out your sketchbookfolder by opening up the Preferences tab in the Arduino IDE.

If you're not familiar with installing Arduino libraries, please visit our tutorial: All About Arduino Libraries!
Next we will connect up the PCBs, we soldered solid-core wires from the 5 connection fingers and plug them into an Arduino. We suggest starting with an Uno since its guaranteed to work

Connect the wires:

  • 5V goes to the 5V power pin on the Arduino
  • GND goes to and GND ground pin
  • SCL goes to the I2C clock pin, on an Uno this is also known as A5
  • SDA goes to the I2C data pin, on an Uno this is also known as A4
  • We connect the INT interrupt pin to A2 - this pin isn't used in our demo code so you can leave it unconnected if you wish.
Now open up the Arduino IDE and open up the File->Examples->Adafruit_Trellis->TrellisTest example sketch and upload it to your Arduino

This sketch tests a single tile, with the default 0x70 address. It will light up all the LEDs in order and then turn them off. Then you can place the elastomer on top & press buttons to toggle buttons

Library reference

The trellis example sketch shows you just about everything you can do with the Trellis library.

Creating the objects

Each panel has its own named object called an Adafruit_Trellis, created like this:
Adafruit_Trellis matrix = Adafruit_Trellis();
when you have many Adafruit_Trellis objects, we suggest creating a TrellisSet which will read all the buttons at once, write all the LEDs at once, etc. Each TrellisSet is given the names of the Adafruit_Trellis objects you created, up to 8.
Adafruit_TrellisSet trellis = Adafruit_TrellisSet(&matrix0, &matrix1, &matrix2, &matrix3);
When you call begin to start the Adafruit_TrellisSet object, pass in the addresses that correspond to your PCBs (see the next page on how to set addresses). The addresses range from 0x70 to 0x77
trellis.begin(0x70, 0x71, 0x72, 0x73); // or four!

Controlling LEDs

You can set or clear LEDs with trellis.setLED(n) and trellis.clrLED(n) where n is the LED # from 0 to (number of Trellis')*16-1. So if you have 4 Trellis's in a set, thats 0 to 63

You can only turn LEDs on or off, there is no grayscale or PWM on this chip

When you are done setting and clearing LEDs you must call writeDisplay() to send the data to all the boards: trellis.writeDisplay() will write all Trellis PCBs in the set at once

You can also test if an LED is lit with trellis.isLED(n) - will return true if the LED is lit, and false if it isn't

Reading Switches


You can read buttons by calling
trellis.readSwitches()
It will return true if there has been any change in switches since the last time you called readSwitches(). So if some buttons were pressed and now aren't or vice versa, it will return true. If nothing's changed, it will return false
Once you've read the switches, you can query the TrellisSet about them.
If you'd like to know if a key #k (k is 0..(number of Trellis')*16-1) is currently pressed, call
isKeyPressed(k)
If you want to know if there was a change in the button, you can ask if it's been pressed or released since the last call to readSwitches()
trellis.justReleased(k)
trellis.justPressed(k)

Adding support for more tiles


You can tile up to 8 Trellis PCBs together (see the next page for the mechanical connections of doing so)

Make sure each Trellis has a unique address ID!

Open up the TrellisTest sketch and change the following

Make more objects

After
Adafruit_Trellis matrix0 = Adafruit_Trellis();
add as many matrices as you like, each with a unique name, e.g.
Adafruit_Trellis matrix1 = Adafruit_Trellis();
Adafruit_Trellis matrix2 = Adafruit_Trellis();
etc...

Make a bigger set

Next we will make a set of matrices. Instead of
Adafruit_TrellisSet trellis = Adafruit_TrellisSet(&matrix0);
update it to add up to 8 matrix names you defined. For example, 4 panels looks like:
Adafruit_TrellisSet trellis = Adafruit_TrellisSet(&matrix0, &matrix1, &matrix2, &matrix3);

Say the number

Change this number from 1 to whatever # you are addressing
// set to however many you're working with here, up to 8
#define NUMTRELLIS 1

Begin again
Change the begin() call to add more addresses. Originally we only have the default 0x70 address:
trellis.begin(0x70); // only one
Change this to add all the addresses you are using:
trellis.begin(0x70, 0x71, 0x72, 0x73); // four!

That's it! Now your TrellisSet will know and control up to 8 panels.

This guide was first published on Dec 06, 2013. It was last updated on Dec 06, 2013. This page (Connecting) was last updated on Nov 16, 2019.