- Support for 4x20 LCD Display and large number display
- Brightness and contrast adjustment with remote
- (OPUS/Wolfson WM8741) DAC volume control: remote and rotary encoder
- (OPUS/Wolfson WM8741) DAC random filter selection 1 to 5 with remote
- (OPUS/Wolfson WM8741) DAC upsampling selection (L, M, H -this is the OSR setting)
- I2C level shifting (5V to 3.3V)
- Optimized power-up sequence

Saturday, June 13, 2009

I2C Address and R/W bit

I was reviewing my code and could not remember why the register addresses I defined in the code was different from the register addresses defined in the data sheet of the WM8741. After an hour reviewing the data sheet and the I2C protocol, I finaly realized that I2C address are 7 bit and the 8th bit is the Read/Write bit.

Since all the registers of the WM8741 are all write registers (R/W bit=0), they all end with zero. So the address value that you send in the I2C protocol is the 7 bit address plus the R/W bit, so the 8-bit values ends with zero.


7-bit Address plus R/W bit

00h=0000000 plus R/W bit = 00000000 = 00h or 0x00
plus R/W bit = 00000010 = 02h or 0x02
02h=0000010 plus R/W bit = 00000100 = 04h or 0x04

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