I have reviewed the specification on pages 15 and 16 for the ADIS16488 that describe the integrated outputs for the rotation rate and aceleration. These values appear to be the integrals of the rate and acceleration over the sample interval as indicated by the output rate DEC_RATE. The documentation presents equations that indicates that there is a trapezoidal integration of the rate and acceleration to get the DELTANG and DELTVAL results. What is not clear is the integration rate of the implied internal summation to get the integrated output. Ideally, the internal integration would at the high internal sampling frequency of 2.46kHz. Therefore if the DEC_RATE is set to achieve 98.4Hz, we would internally sum DEC_RATE+1 = 25 samples to get the 98.4Hz (delta_T =0.01016secs) output. However, based on the equations for the output as presented in the spec, integration would be simply the average of the rate or acceleration as defined by the (start+end)/2 of the samples.

Can you please explain how this integration works ...

--- Jim

from page 20 of the spec ...

The output sample rate is equal to 2460/(DEC_RATE + 1).

DIN = 0x8D00 to reduce the output sample rate to 98.4 SPS (2460 ÷ 25).

Hello Jim,

Sorry that this slipped into this week. We are going to update the datasheet to reflect the following, which I think, agrees with what you were hoping for. I hope that this helps. Best, NevadaMark

## Delta Angles

The delta angle outputs represent an integration of the gyroscope measurements and use the following formula for all three axes (x-axis displayed):

where:

ω

_{x}= x-axis rate of rotation (gyroscope)fs = sample rate

n = sample time, prior to the decimation filter

D = decimation rate = D = DEC_RATE+1

When using the internal sample clock, f

_{S}will be equal to 2460SPS. When using the external clock option, f_{S}will be equal to the frequency of the external clock. In this mode, a 252MHz sample clock measures the time between active edges, in order to determine the actual sample rate for this calculation. See Table 55 and Figure 20 for more information on the DEC_RATE register (decimation filter). The registers that use the x_DELTANG_OUT format are the primary registers for the delta angle calculations. When processing data from these registers, use a 16-bit, twos complement data format (see Table 24, Table 25, and Table 26). Table 27 provides x_DELTANG_OUT digital coding examples.Table 24. X_DELTANG_OUT (Page 0, Base Address = 0x42)

BitsDescription[15:0]

X-axis delta angle data; twos complement,

±720° range, 0° = 0x0000, 1 LSB = 720°/2

^{15}= ~0.022°Table 25. Y_DELTANG_OUT (Page 0, Base Address = 0x46)

BitsDescription[15:0]

Y-axis delta angle data; twos complement,

±720° range, 0° = 0x0000, 1 LSB = 720°/2

^{15}= ~0.022°Table 26. Z_DELTANG_OUT (Page 0, Base Address = 0x4A)

BitsDescription[15:0]

Z-axis delta angle data; twos complement,

±720° range, 0° = 0x0000, 1 LSB = 720°/2

^{15}= ~0.022°Table 27. x_DELTANG_OUT Data Format Examples

Angle (°)DecimalHexBinary+720 × (2

^{15}− 1)/2^{15}+32,767

0x7FFF

0111 1111 1110 1111

+1440/2

^{15}+2

0x0002

0000 0000 0000 0010

+720/2

^{15}+1

0x0001

0000 0000 0000 0001

0

0

0x0000

0000 0000 0000 0000

−720/2

^{15}−1

0xFFFF

1111 1111 1111 1111

−1440/2

^{15}−2

0xFFFE

1111 1111 1111 1110

−720

−32,768

0x8000

1000 0000 0000 0000