driver for adafruit led backpack

display.c

#include "display.h"
#include "third_party/i2cmaster.h"

static const uint8_t number_table[] = {
    0x3F, 0x06, 0x5B, 0x4F, 0x66, 0x6D, 0x7D, 0x07, 0x7F, 0x6F, 0x77, 0x7C,
    0x39, 0x5E, 0x79, 0x71 };

void init_display(int address) {
  i2c_start_wait(address + I2C_WRITE);
  i2c_write(0x21);
  i2c_stop();

  i2c_start_wait(address + I2C_WRITE);
  i2c_write(0x81);
  i2c_stop();

  i2c_start_wait(address + I2C_WRITE);
  i2c_write(0xef);
  i2c_stop();
}

void display_digits(int address, int a, int b, int c, int d, int colon,
    int a_dot, int b_dot, int c_dot, int d_dot) {
  i2c_start_wait(address + I2C_WRITE);
  i2c_write(0x0);
  i2c_write(number_table[a % 16] | (a_dot ? _BV(7) : 0));
  i2c_write(0x0);
  i2c_write(number_table[b % 16] | (b_dot ? _BV(7) : 0));
  i2c_write(0x0);
  if (colon) {
    i2c_write(0xff);
  }
  else {
    i2c_write(0x0);
  }
  i2c_write(0x0);
  i2c_write(number_table[c % 16] | (c_dot ? _BV(7) : 0));
  i2c_write(0x0);
  i2c_write(number_table[d % 16] | (d_dot ? _BV(7) : 0));
  i2c_write(0x00);
  i2c_write(0x00);
  i2c_write(0x00);
  i2c_write(0x00);
  i2c_write(0x00);
  i2c_write(0x00);
  i2c_write(0x00);
  i2c_stop();
}