- 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

Monday, March 30, 2009

Opto Isolation for I2C

In audio, one of the main concerns is to eliminate any source of noise. The I2C line may be a source of noise as it is connected to a micro controller, LCD and other devices such as an RF remote.

Optocouplers are a standard way to isolate circuits. With I2C, the use of optocoplers is a bit more challenging because the signals are bi-directional. One way to do it is to use an I2C bi-directional buffer and a couple of opto-isolators as shown in this image:

Recently, Analog Devices released a fully integrated solution, the ADUM1250/2250. An 8-pin/16-pin chip solution with transformer-based isolation:

The technology is called "iCoupler Technology" and claims to be superior to pure optical or pure transformer isolation. The following diagram gives an idea on the technology:

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