Making the Si4844 works with 5V Arduino UNO or similar
The SI4844 device works with +3.3V only. If you are not using a +3.3V version of Arduino, you have to use a kind of converter. I have tested it with success by using the I2C Multiplexer TCA9548A and Arduino UNO. However, during my attempts, just using a regular bidirectional voltage converter was not enough. I mean, It has not worked properly due to I2C communication requirement (I guess). So I have used the TCA9548A as a I2C bidirectional converter and a regular voltage converter to the digital pins, RESET and INTERRUPT. If you follow the idea of the schematic below you will get success.
I used what I had in my hands. However, I think there are other kind of components or methods that can be better than my approach.
The schematic below shows that approach.
IMPORTANT: You have to include in your sketch (setup function) these three lines:
Wire.beginTransmission(0x70);
Wire.write(1 << channel);
Wire.endTransmission();
where channel is the port that you have choosen to connect the arduino to the Si4844. The schematic above shows channel (port) 0. So, the code should be:
Wire.beginTransmission(0x70);
Wire.write(1); // Yes. In this particular case just Wire.write(1). See the C/C++ "<<" for more detail.
Wire.endTransmission();
if you choose the port 7
Wire.beginTransmission(0x70);
Wire.write(1 << 7);
Wire.endTransmission();
The table below show the possibilities to select an I2C channel on TCA9548A.
| channel / port | byte to send |
|---|---|
| 0 | 00000001 |
| 1 | 00000010 |
| 2 | 00000100 |
| 3 | 00001000 |
| 4 | 00010000 |
| 5 | 00100000 |
| 6 | 01000000 |
| 7 | 10000000 |
You can also implement the function below in your code
inline void selectChannel(byte ch) {
if ( ch < 8 ) {
Wire.beginTransmission(0x70); // The const hex 0x70 is the TCA9548A I2C address
Wire.write(1 << ch);
Wire.endTransmission();
}
}
References
- TCA9548ALow-Voltage8-ChannelI2C Switchwith Reset
- TCA9548A Wiring & Test
- Adafruit TCA9548A 1-to-8 I2C Multiplexer Breakout
- Understanding the I2C Bus