Using three ADXL345's on a single Arduino

Forum 2005-2010 (read only) Hardware Interfacing
1

Forgive me if this has been covered already...I tried a search and didn't find what I was looking for.

Essentially, I need to create a motion capture system using three ADXL345 accelerometers. It seems, though, that I need at least 18 analog input pins to accomplish this, and no Arduino board exists which features that many input pins.

Am I missing something? Or, perhaps, it's possible to use some sort of ADC to use the digital pins as analog pins?

Thanks.

2

Do you need to use analog output accelerometers? You could get 3 I2C devices.
I believe some of the ADI and Freescale devices have address two address pins.

(* jcl *)

3

Could you use an I2C port expander like this one: SparkFun I2C Expander Breakout - PCF8575 - BOB-08130 - SparkFun Electronics ?

I don't know if it can do analog...