MPR083 datasheet(32/56 Pages) FREESCALE

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Embedded Software Description

Blood Pressure Monitor Design Reference Manual, Rev. 0

4-2

Freescale Semiconductor

The fact that each module has its own .c file simplifies the process of adding and eliminating modules in

the code.

4.4

Software

4.4.1

Blood Pressure Measurement

The blood pressure measurement is part of the hardware independent layer of the application. This module

is set up to work as a state machine that is called from the main loop. When a measurement is not being

taken, the system is in an IDLE state — when a measurement starts, the state machine is changed. It then

enables the pressure sensor, RTC, and TPM modules. Next, the system begins to inflate the cuff according

to the necessary measurement. Whenever a measurement is being taken, the RTC takes an ADC

measurement of the cuff pressure and of the high pass filter every 1 ms. This measurement is what is used

by the blood pressure state machine to adjust the level of inflation by controlling the motors, using a TPM

module in the MCU. After the measurement finishes, the system disables all unused modules and goes

back to the IDLE state.

4.4.2

Capacitive Touch

The sensor is controlled using a state machine which runs in the application’s main loop. It is called

periodically and is non-blocking. This state machine uses the hardware abstraction layers that manage the

IIC and KBI modules of the microcontroller. This figure shows the state machine being used:

MPR083 Datasheet(PDF) 32 Page - Freescale Semiconductor, Inc