BMA222 Bosch Sensortec, BMA222 Datasheet - Page 25

• Manufacturer Part Number: BMA222
• Description: 3-AXIS ACCELEROMETER DIGITAL SMD
• Manufacturer: Bosch Sensortec

Specifications of BMA222

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 828-1025-2

4.8.5 Any-motion (slope) detection
Any-motion detection uses the slope between successive acceleration signals to detect
changes in motion. An interrupt is generated when the slope (absolute value of acceleration
difference) exceeds a preset threshold. It is cleared as soon as the slope falls below the
threshold. The principle is made clear in figure 6.
The threshold is set with the value of register (0x28) slope_th. 1 LSB of (0x28) slope_th
corresponds to 1 LSB of acceleration data. Therefore, an increment of (0x28) slope_th is 3.91
mg in 2g-range (7.81 mg in 4g-range, 15.6 mg in 8g-range and 31.3 mg in 16g-range). And the
maximum value is 996 mg in 2g-range (1.99g in 4g-range, 3.98g in 8g-range and 7.97g in 16g-
range).
The time difference between the successive acceleration signals depends on the selected
bandwidth and equates to 1/(2*bandwidth) (Δt=1/(2*bw)). In order to suppress failure signals,
the interrupt is only generated (cleared) if a certain number N of consecutive slope data points is
larger (smaller) than the slope threshold given by (0x28) slope_th. This number is set by the
(0x27) slope_dur bits. It is N = (0x27) slope_dur + 1 for (0x27).
Example: (0x27) slope_dur = 00b, …, 11b = 1decimal, …, 4decimal
Rev. 1.0
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Note: Specifications within this document are subject to change without notice.
acceleration
slope_th
slope
INT
acc(t
0
−1/(2*bw))
Figure 6: Principle of any-motion detection
acc(t
slope_dur
slope(t
0
)
0
)=acc(t
slope_dur
Data sheet
0
BMA222
)−acc(t
Page 25
0
−1/(2*bw))
time
time
time
Bosch Sensortec
07 March 2011