Amplifier with i2c control

Device Code
1

I got a little amplifier from adafruit which got build in i2c control. (http://learn.adafruit.com/adafruit-20w-stereo-audio-amplifier-class-d-max9744/digital-control)

But how do I make the imp communicate with it? I have attached Vi2c to the impee’s 3V3, SCL to pin 8, and SDA to pin 9.

I then tried to mess around a bit with this

hardware.i2c89.configure(CLOCK_SPEED_400_KHZ); hardware.i2c89.write(0x4B, "10");

But so far no luck, anyone with more knowledge of i2c who can help me with this?

2

I am also a bit new, but I will give it a try

page 17 of the datasheet

datasheet

The address 0x4B represents “1001011”

“1001” is standard, then “0”, then “11” indicating both pins that woudl create a configurable address are pulled high

This is a 7-bit address but a byte is 8 bits. you need to Left-shift this one

1001011_

and the “_” is replaced by 1 or zero depending whether you are reading or writing.

so

10010111 => 0x97 – I think read
or
10010110 => 0x96 - I think write

are the two addresses to use.

Then you have to add your command and value into a string. have a look at the i2c write documentation of imp for an example of how to append a command with data.

I like to use this tool for binary, hex and decimal conversions.

http://www.mathsisfun.com/binary-decimal-hexadecimal-converter.html

3

oh, sorry. just realized this is a simpler device and I can do better. try this.

again, new at this but have successfully talked spi and i2c branching off example code from others

`function testwritei2c(_volume) {

local address   = 0x96;
local volume = _volume;
if (volume>63){
    volume=63;
}
if (volume<0){
    volume=0;
}

hardware.i2c89.write(address, format("%c%c", volume>>8, volume&0xff));

}`

4

MikeyDK, as mjkuwp94 says, you need to multiply the given I2C address by 2 to use it with the Imp. I usually do it this way:

local device_address = 0x4B << 1; // Shift bits left by one bit i2c <- hardware.i2c89; i2c.configure(CLOCK_SPEED_400_KHZ);

You don’t have to worry about the value of the new bit zero; the imp will take care of that for you when you read or write data from/to your device.

5

Awesome!!! It works!! :smiley:

Used the code from mjkuwp94, then replaced the address with how smittytone does it, so it is easier for me to read. (looking exactly like in the tutorial)

6

Excellent! Well done.

You’ll soon be multiplying I2C addresses by 2 and keying the result straight into your code, but IMHO it’s still good to show in code how it works.