Requires large current greater than microcontroller

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Unformatted text preview: de – add external buffer/amplifier) ECHO requires a pull-up resistor (determine current that needs to flow into microcontroller pin - size resistor so proper voltage is on pin # Ω # ! "Ω $ " 1 42 ' - Detecting a change in compass direction 7 Oscillator must be set to match detector 4 bits change from 0001 to 0011 to 0010 to 0110 to 0100 … Always alternating between one bit on and two bits on Parity tree can detect difference between one and two bits being asserted XOR tree of four bits (one TTL SSI package) Output must change at least once for every change in orientation Use interrupts to detect changes e.g., NE E SE 1100 0100 0110 0 1 0 N E S W * - : $ $ , # 7 turn on emitter sleep for 600us val_on = read detector turn off emitter sleep for 600us val_off = read detector return ( val_on & ~val_off ) timer goes off wake timer goes off wake Mostly in main turn on emitter Using interrupt handlers set timer sleep timer goes off val_on = read detector turn off emitter reset timer sleep timer goes off (again) val_off = read detector return ( val_on & ~val_off ) wake 7 8 7 Micro-electro-mechanical system that measures force Always sending out IR Detector drives LED (guaranteed to match frequency) F = ma (I. Newton) Measured as change in capacitance between moving plat...
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