What I have now are two ADXL337 accelerometers, feeding an ADS1256 ADC, which is on an SPI port. The purpose is to sense the tilt angles of the two accelerometers. I am not satisfied with the results, since it seems like a lot of work in the software---reading the ADC, scaling, averaging, etc, etc.
I am trying to replace the two ADXL337 with two ADXL313, which seem a lot simpler in my application. The ADXL313 can be configured for 3 or 4 wire SPI, or I2C and does the ADC on chip. Since I am already using SPI I looked at that first, but because of the limited wires on the existing cables I would have to use 3 wire SPI, and still have to swap out some connectors.
After further research I see that using I2C would be easier, as I can use the existing cables and connectors, and it is plenty fast enough for my application.