Arduino Code

The Arduino code presented below works well on GEMMA v2.. But if you have an M0 board you must use the CircuitPython code on the next page of this guide, no Arduino IDE required!
If this is your first time using Gemma, work through the Introducing Gemma guide first; you need to customize some settings in the Arduino IDE.

Be sure to check out Phil Burgess's space invader pendant guide for getting the source code on to GEMMA properly.
Once you have your GEMMA/Trinket profiles installed in your Adafruit Arduino IDE, copy this code into a new sketch in Arduino and save it as matrix.ino.
// Trinket/Gemma + LED matrix backpack jewelry.  Plays animated
// sequence on LED matrix.  Press reset button to display again,
// or add optional momentary button between pin #1 and +V.
// THERE IS NO ANIMATION DATA IN THIS SOURCE FILE, you should
// rarely need to change anything here.  EDIT anim.h INSTEAD.

#define BRIGHTNESS   12 // 0=min, 15=max
#define I2C_ADDR   0x70 // Edit if backpack A0/A1 jumpers set

#include <TinyWireM.h>
#include <avr/power.h>
#include <avr/sleep.h>
#include "bmo.h"       // Animation data is located here

static const uint8_t PROGMEM reorder[] = { // Column-reordering table
    0x00,0x40,0x20,0x60,0x10,0x50,0x30,0x70,0x08,0x48,0x28,0x68,0x18,0x58,0x38,0x78,
    0x04,0x44,0x24,0x64,0x14,0x54,0x34,0x74,0x0c,0x4c,0x2c,0x6c,0x1c,0x5c,0x3c,0x7c,
    0x02,0x42,0x22,0x62,0x12,0x52,0x32,0x72,0x0a,0x4a,0x2a,0x6a,0x1a,0x5a,0x3a,0x7a,
    0x06,0x46,0x26,0x66,0x16,0x56,0x36,0x76,0x0e,0x4e,0x2e,0x6e,0x1e,0x5e,0x3e,0x7e,
    0x01,0x41,0x21,0x61,0x11,0x51,0x31,0x71,0x09,0x49,0x29,0x69,0x19,0x59,0x39,0x79,
    0x05,0x45,0x25,0x65,0x15,0x55,0x35,0x75,0x0d,0x4d,0x2d,0x6d,0x1d,0x5d,0x3d,0x7d,
    0x03,0x43,0x23,0x63,0x13,0x53,0x33,0x73,0x0b,0x4b,0x2b,0x6b,0x1b,0x5b,0x3b,0x7b,
    0x07,0x47,0x27,0x67,0x17,0x57,0x37,0x77,0x0f,0x4f,0x2f,0x6f,0x1f,0x5f,0x3f,0x7f,
    0x80,0xc0,0xa0,0xe0,0x90,0xd0,0xb0,0xf0,0x88,0xc8,0xa8,0xe8,0x98,0xd8,0xb8,0xf8,
    0x84,0xc4,0xa4,0xe4,0x94,0xd4,0xb4,0xf4,0x8c,0xcc,0xac,0xec,0x9c,0xdc,0xbc,0xfc,
    0x82,0xc2,0xa2,0xe2,0x92,0xd2,0xb2,0xf2,0x8a,0xca,0xaa,0xea,0x9a,0xda,0xba,0xfa,
    0x86,0xc6,0xa6,0xe6,0x96,0xd6,0xb6,0xf6,0x8e,0xce,0xae,0xee,0x9e,0xde,0xbe,0xfe,
    0x81,0xc1,0xa1,0xe1,0x91,0xd1,0xb1,0xf1,0x89,0xc9,0xa9,0xe9,0x99,0xd9,0xb9,0xf9,
    0x85,0xc5,0xa5,0xe5,0x95,0xd5,0xb5,0xf5,0x8d,0xcd,0xad,0xed,0x9d,0xdd,0xbd,0xfd,
    0x83,0xc3,0xa3,0xe3,0x93,0xd3,0xb3,0xf3,0x8b,0xcb,0xab,0xeb,0x9b,0xdb,0xbb,0xfb,
    0x87,0xc7,0xa7,0xe7,0x97,0xd7,0xb7,0xf7,0x8f,0xcf,0xaf,0xef,0x9f,0xdf,0xbf,0xff };

void ledCmd(uint8_t x) { // Issue command to LED backback driver
  TinyWireM.beginTransmission(I2C_ADDR);
  TinyWireM.write(x);
  TinyWireM.endTransmission();
}

void clear(void) { // Clear display buffer
  TinyWireM.beginTransmission(I2C_ADDR);
  for(uint8_t i=0; i<17; i++) TinyWireM.write(0);
  TinyWireM.endTransmission();
}

void setup() {
  power_timer1_disable();    // Disable unused peripherals
  power_adc_disable();       // to save power
  PCMSK |= _BV(PCINT1);      // Set change mask for pin 1
  TinyWireM.begin();         // I2C init
  clear();                   // Blank display
  ledCmd(0x21);              // Turn on oscillator
  ledCmd(0xE0 | BRIGHTNESS); // Set brightness
  ledCmd(0x81);              // Display on, no blink
}

uint8_t rep = REPS;

void loop() {

  for(int i=0; i<sizeof(anim); i) { // For each frame...
    TinyWireM.beginTransmission(I2C_ADDR);
    TinyWireM.write(0);             // Start address
    for(uint8_t j=0; j<8; j++) {    // 8 rows...
      TinyWireM.write(pgm_read_byte(&reorder[pgm_read_byte(&anim[i++])]));
      TinyWireM.write(0);
    }
    TinyWireM.endTransmission();
    delay(pgm_read_byte(&anim[i++]) * 10);
  }

  if(!--rep) {             // If last cycle...
    ledCmd(0x20);          // LED matrix in standby mode
    GIMSK = _BV(PCIE);     // Enable pin change interrupt
    power_all_disable();   // All peripherals off
    set_sleep_mode(SLEEP_MODE_PWR_DOWN);
    sleep_enable();
    sei();                 // Keep interrupts disabled
    sleep_mode();          // Power down CPU (pin 1 will wake)
    // Execution resumes here on wake.
    GIMSK = 0;             // Disable pin change interrupt
    rep   = REPS;          // Reset animation counter
    power_timer0_enable(); // Re-enable timer
    power_usi_enable();    // Re-enable USI
    TinyWireM.begin();     // Re-init I2C
    clear();               // Blank display
    ledCmd(0x21);          // Re-enable matrix
  }
}

ISR(PCINT0_vect) {} // Button tap
Create a new window and paste in the BMO animation code and save it as bmo.h in the same directory as the matrix sketch.

You may have to remove the .ino extension that gets added to the bmo.h file making it bmo.h.ino, remove that last .ino appending to just .h. Close the IDE and reopen it. The matrix sketch should show the bmo.h file in a tab.

Goto the tools file menu and select the Adafruit Gemma 8MHz profile under the Board drop down menu. Select USBTinyISP under the Programer drop down in the tool file menu.

Plug in a mini USB cable to the Gemma and connect it to your computer. Wait until you see a red blinkling LED on the Gemma and then hit the left arrow icon button to upload the code.
If you get a message in the IDE "Done Uploading" the code successfully uploaded to the GEMMA!
      // Animation data for Trinket/Gemma + LED matrix backpack jewelry. 
#define REPS 255 // Number of times to repeat the animation loop (1-255)
const uint8_t PROGMEM anim[] = {
  
  B11111111, // 1 frame
  B10011001,
  B10011001,
  B11111111,
  B10000001,
  B11000011,
  B11100111,
  B11111111,
  25, // 0.25 second delay
  
  B11111111, // 2 frame
  B10011001,
  B10011001,
  B11111111,
  B10111101,
  B10111101,
  B11000011,
  B11111111,
  25, // 0.25 second delay
  
  B11111111, // 3 frame
  B10011001,
  B10011001,
  B11111111,
  B10000001,
  B11000011,
  B11100111,
  B11111111,
  25, // 0.25 second delay
  
  B11111111, // 4 frame
  B10011001,
  B10011001,
  B11111111,
  B10111101,
  B10111101,
  B11000011,
  B11111111,
  25, // 0.25 second delay
  
  B11111111, // 5 frame
  B10011001,
  B10011001,
  B11111111,
  B11111111,
  B11111111,
  B10000001,
  B11111111,
  25, // 0.25 second delay
  
  B11111111, // 6 frame
  B10011001,
  B10011001,
  B11111111,
  B11100111,
  B11011011,
  B11100111,
  B11111111,
  25, // 0.25 second delay
  
  B11111111, // 7 frame
  B10111101,
  B00011000,
  B10111101,
  B11100111,
  B11011011,
  B11100111,
  B11111111,
  25, // 0.25 second delay
  
  B11111111, // 8 frame
  B11111111,
  B00011000,
  B11111111,
  B11100111,
  B11011011,
  B11100111,
  B11111111,
  25, // 0.25 second delay
  
  B11111111, // 9 frame
  B10111101,
  B00011000,
  B10111101,
  B11100111,
  B11011011,
  B11100111,
  B11111111,
  25, // 0.25 second delay
};
    

Writing Custom LED Animations

Check out Phil Burgess's Space invader guide for a great break down on how to write your own LED animations.

Animation Tool for Adafruit 8x8 LED Matrix

Check out this awesome website for building letter based LED animations. You simply click on letters to build an animation which can then be out putted to animation data for the Trinket/Gemma. It's awesome!
This guide was first published on Feb 20, 2014. It was last updated on Feb 20, 2014. This page (Arduino Code) was last updated on Dec 12, 2018.