[Gdeaver]

So far the discussion has been on low range accelerometers. Remember, it's on a robot and there may be times when there is a impact or bump that will drive the unit to saturation. It can take a considerable amount of time to recover from a saturated condition. It's enough to affect the integration. Accelerometers are also excellent vibration sensors. One thing that is often over looked is the natural resonance frequency of the sensor. Both the chip package and the sensor have a resonate point that is high enough not to worry about but your going to have to mount the chip on a carrier. You have to worry about the resonance point of the chip-carrier-mounting system.
Glue your chip to the board. Use a thick high grade PC board. More ridged the better. Use some isolation mounting to mount the board to the bot and pay attention to what part of the robot you mount it to. Try to isolate it from the drive train vibration. I think you might have better results if you went to a mid range analog unit. Run the output through and op amp with a gain of one and a 400 HZ low pass filter. Mount the pic18, op amp and sensor on a small ridged carrier that is mounted to a ridge large mass part of the robot with some isolation mounting hardware. Over sample in software to further reduce noise. Let the pic coproc do the calculations and send a periodic update to the FRC .

The Freescale MMA3201D has a low pass fiter on the chip.