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

2.3 Microphone

The input signal is captured by a Panasonic WM-61A microphone that has a frequency response between 20 Hz and 20 kHz and can operate at voltages up to 10 V. The microphone has a signal-to-noise ratio of approximately 60 dB. The microphone is turned on every 2 ms when the input signal needs to be captured. This on-and-off mechanism is controlled in software by port pin P4.0 of the MSP430 MCU, which provides the supply voltage of DVCC to the microphone. The maximum current consumption during this capture is approximately 0.5 mA. The microphone is physically disabled by placing a jumper on header X3.