The ADXL210 accelerometers measure bovine motion for a total of four measured axes. One of the measurements is redundant. 

The accelerometers output a 0- to 1-ms pulse that’s indicative of acceleration from –10 to 10 g. Each axis is connected to one of the Timer0 input capture inputs. The input capture service routine is programmed as an FIQ so that it can interrupt inside the 10-ms logging loop. 

When it starts, input capture code records the time of the pulse using Timer0 counting at 15 MHz. The software waits for the first rising edge and then records the start time, the time of the falling edge (T1), and the time of the start of the next waveform (T2). T1 and T2 are divided to compensate for temperature and drift. The final value is presented as the acceleration value and stored in secondary memory.

Currently, 14 bits of resolution are used. The dropped bits are below the noise level experienced by a static accelerometer. A compile time definition (#define) can be changed to increase the significant bits to a maximum of 16.