SCA3000 datasheet(13/43 Pages) VTI

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SCA3000 Series

VTI Technologies Oy

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Doc.Nr. 8257300A.07

Rev.A.07

2.5.3

Examples

A simple example of output ring buffer usage:

Write "10000000" (C0h) into MODE register (enable output ring buffer, BUF_EN = '1')

Acceleration data can be read normally

INT-pin is activated when buffer is ½ full, see section 2.7 for detailed INT-pin information.

In the next example, the output Ring Buffer is configured to sample only the Z-axis acceleration

data with 8 bit resolution and reduced data rate (only every second sample is stored into output

ring buffer). In addition, the SCA3000 is configured to give an interrupt when the output ring buffer

is ¾ full:

Write "11000000" (C0h) into the MODE register (enable output ring buffer, BUF_EN = '1',

set data length to 8 bits, BUF_8BIT = '1')

Write "00000000" (00h) into UNLOCK register

Write "01010000" (50h) into UNLOCK register

Write "10100000" (A0h) into UNLOCK register

Write "00001011" (0Bh) into CTRL_SEL register (to select indirect OUT_CTRL register)

Unlock sequence for register lock

Write "00000101" (03h) into CTRL_DATA register (this data is written into OUT_CTRL

Write "10000001" (81h) into INT_MASK register (set buffer interrupt level to ¾ full,

BUF_F_EN = '1', set INT-pin to active high, INT_ACT = '1')

Acceleration data can be read normally for all axis and with full resolution. The buffer data

can be read from BUF_DATA register

INT-pin is activated when the output ring buffer is ¾ full of Z-axis acceleration data, see

section 2.7 for detailed INT-pin information.

2.6

Temperature measurement

2.6.1

Usage

Nine bit temperature information is available in the TEMP_MSB and TEMP_LSB registers, if the

feature is enabled in the product (see Table 1). The TEMP_MSB register must be read before the

TEMP_LSB register in order to get valid temperature data. Registers are updated with the latest

temperature data when accessed. See section 3.3 for register details.

The temperature registers’ typical output at +23 °C is 256 counts and a 1 °C change in temperature

typically corresponds to a 1.8 LSB change in the SCA3000 temperature output. Temperature

information is converted to [°C] as follows

Equation 1

[]

LSB

Temp

dec

−

256

where Temp[°C] is temperature in Celsius and Tempdec is the temperature from TEMP_MSB and

TEMP_LSB registers in decimal format.

2.7

Interrupt function (INT-pin)

2.7.1

Usage

The Motion Detector and Free Fall Detector will generate an interrupt to INT-pin when the

corresponding function is enabled and the interrupt condition is met. The SCA3000's ring buffer will

generate an interrupt when interrupt functionality has been enabled. Setting BUF_F_EN bit in

INT_MASK register "1" results in interrupt when the register is 75% full. Setting BUF_H_EN bit in

INT_MASK register "1" results in interrupt when the register is 50% full.

Setting INT_ALL bit in INT_MASK register will mask all interrupts.

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