SLAAE30 July   2021 MSP430FR2355


  1.   Abstract
  2.   Trademarks
  3. 1PIR Design Description
    1. 1.1 PIR Sensor
    2. 1.2 PIR Signal Chain
      1. 1.2.1 Traditional Motion Detection Signal Chain Design
      2. 1.2.2 Capacitor-Free Signal Chain Design
  4. 2Software
    1. 2.1 Software Architecture
    2. 2.2 Software Flow Chart
    3. 2.3 Power Profile
    4. 2.4 Data Processing
      1. 2.4.1 Digital Signal Conditioning
      2. 2.4.2 Low-Pass Filter for Temperature Drift
      3. 2.4.3 Spikes and Noise
      4. 2.4.4 Motion Detection Function
  5. 3Hardware and Schematic
    1. 3.1 MSP430FR2355
    2. 3.2 Schematic
  6. 4Results
    1. 4.1 Distance: 15 ft (4.5 m)
    2. 4.2 Distance: 22.5 ft (6.9 m)
    3. 4.3 Distance: 36.5 ft (11.1 m)
  7. 5Summary
  8. 6References


Motion detection is valuable in many battery powered building automation applications, from basic security sensors to fully interactive camera systems. These systems rely on accurate, low power motion detection to maximize battery life by keeping powerful processors and wireless radios shut down when not needed. This design provides a low power, high-performance, and very cost competitive motion detection solution using an analog passive infrared (PIR) motion sensor and the MSP430FR2355. The MSP430FR2355 has integrated Smart-Analog Combos (SACs) that include operational amplifiers (OpAmps) and digital to analog convertors (DACs). The SACs can provide the PIR sensor’s entire signal chain, integrated inside the MSP430. The SACs are software configurable, allowing the signal chain to be easily adjusted for higher sensitivity and range, digital feedback loops, and optimized for low power performance. This application report addresses ultra low power, high performance PIR design theory and test results using the MSP430FR2355.