User Manual

ZSTAR3 Sensor Board Description

ZSTAR3 Reference Design Manual, Rev. 0.1

Freescale Semiconductor 3-17

Preliminary

Figure 3-3. ZSTAR3 Sensor Board Software Overview

For the Sensor Board operation, several of the MC13213’s hardware modules are used: Analog to Digital

Converter (ADC), Synchronous Peripheral Interface (SPI), External Interrupt Request (IRQ), Keyboard

Interrupts and General Purpose Input/Output (GPIO).

3.2 Accelerometric sensor sw controller

Reading of XYZ levels and all others operation with sensor is depends on current assembled sensor. The

ZSTAR3 sensor board supports two types of Freescale accelerometric sensors, analogue(MMA736xLT)

and digital(MMA745xL). Assembly sensor is powered by IO pins of MCU, this solution allow reach a

lowest power consumtion in sleep mode.

3.2.1 Double sensor support software model

All common control functions of sensor are physically create as two individual function. First for analogue

and second for digital sensor. Main software is using only volatile pointers on this function, that are

assigned within initialization of program, by ”

Recognise_Sensor() “ function. This function recognises an

assembled sensor and assigns right functions address to volatile RAM pointers. For example, by this way

analogue sensor is using ADC to read XYZ values of sensor and digital sensor is using digital interface,

but in source code are only one line:

p_Read_Accelerometer((void*) &(accel_data[0].x)).

3.2.2 Autocalibration process

The software uses for both types of sensor autocalibration process to get offset calibration values. It uses

a simple 0g X, 0g Y, +1g Z acceleration method. The sensor board runs autocalibration process for each g

scale of sensor, and thus uses for each g scale induvidual set of calibration values. For more details see

GPIO

ADC

KBI

Sensor

Buttons

GPIO

Sensor data

collector

Data

buffer

modem

2.4GHz

LED

Protocol

Handler

and

driver