SLAA351A April   2007  – November 2018 MSP430F2232 , MSP430F2232 , MSP430F2234 , MSP430F2234 , MSP430F2252 , MSP430F2252 , MSP430F2254 , MSP430F2254 , MSP430F2272 , MSP430F2272 , MSP430F2274 , MSP430F2274

 

  1.   A Simple Glass-Breakage Detector Using an MSP430™ MCU
    1.     Trademarks
    2. 1 Introduction
    3. 2 Hardware Description
      1. 2.1 Device Specifications
      2. 2.2 Power Supply
      3. 2.3 Microphone
      4. 2.4 LED and Buzzer Alert
      5. 2.5 Interface to CC1100 or CC2500 Devices
      6. 2.6 Operational Amplifiers (OAs)
      7. 2.7 Internal Very-Low-Power Oscillator (VLO)
      8. 2.8 JTAG Interface
      9. 2.9 Current Consumption
    4. 3 Software Description
      1. 3.1 Initialization Routine
      2. 3.2 Timer_A
      3. 3.3 ADC10
      4. 3.4 Signal Analysis
        1. 3.4.1 First Stage of Processing
          1. 3.4.1.1 Signal Averaging, Peak Detection, and Zero Crossings
          2. 3.4.1.2 High-Pass Filtering
        2. 3.4.2 Second Stage of Processing
          1. 3.4.2.1 Frequency Composition Ratio
          2. 3.4.2.2 Peak and Zero-Crossing Count
          3. 3.4.2.3 Glass-Breakage Detect
    5. 4 Hardware Schematic
    6. 5 Test Setup
    7. 6 References
  2.   Revision History

1 Introduction

A glass-breakage detector can help ensure safety in buildings and homes. It is a simple mechanism to detect illegal entry through glass windows and doors. The detector analyzes acoustic signals produced during a glass breakage.

The frequency spectrum of the sounds produced during a glass breakage varies with the type of glass used in these doors and windows. This calls for a variety of solutions tailored to types of glass used. In this application report, typical glass-breakage sounds have been used as a tool to design the alert mechanism. These acoustic signals are analyzed after being captured by an onboard microphone. The steps that follow this capture are explained in detail in this report.

The MSP430F2274 is the microcontroller chosen to do this analysis.[2] Although the processor can operate up to 16 MHz, an active-mode frequency of 12 MHz is used.[1] Furthermore, the CPU operating frequency is changed between 8 MHz and 12 MHz to reduce power consumption. The required peripherals are enabled every 2 ms, only when the input signal needs to be captured, to ensure optimal power management. An optional anti-aliasing filter (AAF) in hardware is activated to ensure the signal spectrum is restricted to 20 kHz. The total power consumption of the system is approximately 80 µA with the AAF enabled and approximately 50 µA with the AAF disabled.

The entire hardware setup, software flow, and test setup are discussed in this report. The following sections provide a complete description of the hardware, software, and test setup. The complete details of this reference design are provided in A Simple Glass-Breakage Detector Reference Design.