API Audio Accessories 7-22-10 User's Guide download pdf (Page 13)

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9700.0031 © Zephyr Technology 2010 2010-07-22

Heart Beat Timestamp (1 to 15)

The heart beat timestamp is a 16 bit unsigned integer, representing the time at which the heart beat occurred, in

milliseconds. (Valid range 0 – 65535ms)

The time used to populate the timestamp rolls over after 65535ms. This should be taken into consideration when

calculating the heart beat interval (RR time).

The R to R data consists of a series of R-detection timestamps with 1 millisecond resolution. The internal clock

rolls over at 65535 ms.

Figure 9 : PQRS Waveform showing the R-R Interval.

The R to R interval is the time between subsequent R peaks in an ECG waveform.

15 values are sent, such that at the fastest valid heart rate (240bpm) 3 consecutive packets can be dropped

without loss of information. Timestamp #1 is the most recent heart beat and timestamp #15 is the oldest.

Distance

The distance is a 16 bit unsigned integer, representing the cumulative distance travelled since the device was

powered on, in 16ths of a meter (valid range 0 to 4095).

The distance travelled rolls over every 256m.

Instantaneous speed

The Instantaneous speed is a 16 bit unsigned integer, representing the Instantaneous speed of the wearer in

steps of 1/256m/s. The valid range is 0 – 4095 steps or 0 to 15.996m/s.

Strides

The strides count is an unsigned byte, representing the number of strides since the unit was powered on. The

valid range is 0 to 255 strides. The number of strides rolls over every 128 strides.

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API Audio Accessories 7-22-10 User's Guide Page 13