- 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

Wednesday, June 24, 2009

Which I/O Expander?

My next project is to control the Texas Instruments SRC4192 chip. This device is an "asynchronous reclocker" and feeds the DAC. Theoretically it reduces jitter because it recreates the clock with a much better on-board oscillator. The device is implemented in a kit board from TwistedPearAudio.

The block diagram is as follows:

In order to interface to the control logic lines, I would need an I/O expander that would communicate with Arduino. Basically you want to swith these lines high or low to select the different configurations and features of the device.

Since there are up to 15 control lines and it needs to support the I2C protocol (to communicate with Arduino) and must by in DIP package (for easy soldering). I would need a 16-port I/O expander in DIP package. Looking over at Digikey, there is just one device in stock that meets the criteria: the PCA9555 by NXP Semiconductors.

It cost $2.13 Application note AN469 explains how these devices work in great detail.

1 comment:

Robot Overlord said...

Sounds ambitious. I can't wait to see how it turns out!