My TDA7439 board

TDA9437

My sound controller board is finally finished. It’s based on the TDA9437 chip. The Dip version of this chip is only available in an annoying SDIP-30 package. It will not fit on a standard prototype board.

The board had inputs for 4 stereo sources (8 pins) and a single stereo output. The IC can select between any of the connected audio sources, and an appropriate gain can be set.
This board also allows a microcontroller to control volume, treble, mid-range and bass. Mute and independent speaker control functions are also available, but I dont think I will use them.

Data transmission from the microprocessor to the TDA7439 and vice versa takes place through the 2-wire I2C bus interface. This consists of the data and clock lines, SDA and SCL. Pull-up resistors to the positive supply voltage must be used (there are no internal pull-ups).

Power up

When powered up with 9 volts, the green LCD should light up. The I2C bus address of the TDA7439 is 0x88 (88hex). This is an 8-bit address, since the arduinos’ wire library only supports 7-bit addresses, an arduino i2c scan will show 0x44. You can use the wire library to address this chip using address 0x44; the extra zero will be added automatically.

Data transmission from the microprocessor to the TDA7439 and vice versa takes place through the 2-wire I2C bus interface. This consists of the data and clock lines, SDA and SCL. Pull-up resistors to the positive supply voltage must be used (there are no internal pull-ups).

Coding

To test and use the board, I used the TDA7439 library :

#include <Wire.h&gt

//Sound Processor chip library
#include <TDA7439.h&gt
TDA7439 equ;

On powerup the output is muted, from the datasheet :

To unmute the board, add this to setup-part in your code.

void setup()
{
equ.setInput(2); // 1 to 4
equ.inputGain(29); // 0 to 30
equ.setVolume(1); // 0 to 48 ( 0 is mute)
//equ.setSnd(0,1); // Bass-7 to +7 
//equ.setSnd(0,2); // Mids -7 to +7
//equ.setSnd(0,3); // Treble -7 to +7
equ.spkAtt(1); // Output attenuation 0 to 79 (db)
}