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65 lines
1.0 KiB
C++
65 lines
1.0 KiB
C++
//
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// FILE: MHZCO2_PWM.ino
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// AUTHOR: Rob Tillaart
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// PURPOSE: demo MHZ library / sensor
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// DATE: 2020-09-01
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/*
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DATASHEET P.?
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Conversion between PWM output and concentration,
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use interrupt pin 3 of Arduino UNO.
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*/
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#include "Arduino.h"
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#include "MHZCO2.h"
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// adjust to calibrate.
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const float MAX_CONCENTRATION = 2000.0;
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volatile uint16_t width;
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void IRQ()
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{
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static uint32_t start = 0;
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int v = digitalRead(3);
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if (v == HIGH) start = millis();
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else width = millis() - start;
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}
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uint16_t PWM_concentration()
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{
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noInterrupts();
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uint16_t TimeHigh = width; // milliseconds
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interrupts();
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uint16_t concentration = round(((TimeHigh - 2) * MAX_CONCENTRATION) * 0.001);
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return concentration;
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}
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void setup()
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{
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Serial.begin(115200);
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Serial.println(__FILE__);
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Serial.print("MHZCO2_LIB_VERSION: ");
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Serial.println(MHZCO2_LIB_VERSION);
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attachInterrupt(digitalPinToInterrupt(3), IRQ, CHANGE);
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}
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void loop()
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{
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Serial.println(PWM_concentration());
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delay(1000);
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}
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// -- END OF FILE --
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