Adafruit I2C 7 segment displays

[gfwilliams]

Posted at 2016-06-07 by @gfwilliams

For displays like this: https://www.adafruit.com/products/881

Using the HT16K33 chip. This one will also interface to the alphanumeric displays like these: https://www.adafruit.com/products/1912

But it won't display anything useful, since you need to send 16 bit values to the controller (in ledShow we just send 0 for the top 8 bits)

Just thought I'd post this up:

var table = {
  " ":0,
  0:0x3F, /* 0 */
  1:0x06, /* 1 */
  2:0x5B, /* 2 */
  3:0x4F, /* 3 */
  4:0x66, /* 4 */
  5:0x6D, /* 5 */
  6:0x7D, /* 6 */
  7:0x07, /* 7 */
  8:0x7F, /* 8 */
  9:0x6F, /* 9 */
  "A":0x77, /* A */
  "B":0x7C, /* b */
  "C":0x39, /* C */
  "D":0x5E, /* d */
  "E":0x79, /* E */
  "F":0x71  /* F */
};

function ledInit() {
 I2C1.setup({scl:B6, sda:B7});
 I2C1.writeTo(0x70, 0x21); // clock on
 I2C1.writeTo(0x70, 0x81); // flash
 I2C1.writeTo(0x70, 0xE0 | 15); // brightness 15
}

function ledShow(n) {
 n="    "+n;
 N = n.substr(-4);
 I2C1.writeTo(0x70, [0,table[n[0]],0,table[n[1]],0,0,0,table[n[2]],0,table[n[3]],0]);
}

function ledFlash(isFlashing) {
  // different numbers give different flash speeds
  I2C1.writeTo(0x70, isFlashing ? 0x83 : 0x81);
}

ledInit();
ledShow("0000"); // or just ledShow(0) to have '0', not '0000'

I did it a while ago and didn't have time to make a module - thought it might help someone.

Attachments:

• 881-00.jpg