I2C experience? Please help :)

Projects Programming
1

I am completely new to I2C, so could someone please explain to me what i recorded with Salae LogicAnalyzer...

Is it writing to address "8" and reading from address "9"?

I am trying to learn I2C to control a factory CD player and display using CDM-M3 4.4 CDdrive, PCF8578 & PCF8579 Colum/Row drivers.

Will this code be the equivalent to what is recorded? At least the first two steps...

#include <Wire.h>

void setup() {
  Wire.begin(); // join i2c bus (address optional for master)
}

void loop() {
  Wire.beginTransmission(8); // transmit to device #8 (0x38)
  // device address is specified in datasheet
  Wire.write(byte(0x00)); // 0 - sends instruction byte
  Wire.write(byte(0x02)); // 2
  Wire.endTransmission(); // stop transmitting
  Wire.requestFrom(9, 3); // request 3 bytes from slave device #9

  delay(500);
}

Salae.png
Salae.png1600×900 103 KB

2

Is it writing to address "8" and reading from address "9"?

Yes. Typically, you would be writing to, and reading from, the same device, though.

3

Snake are you trying to add an AUX port to a cadillac cts 2003-2007? Like a proper port via SPDIF and not a monkey left/right analog splice?? :slight_smile:

4

The wire library uses a 7-bit address and when clocking out that 8th bit, the least significant bit, it is a Read/Write flag.

If you weren't using the wire library you may have to shift the address 1 bit to the left and add in the flag before clocking out the byte. In that case 8 and 9 would be the same address but with the R/W flag swapped.

The way it is written is like the device has two addresses.