mirror of
https://github.com/sigmasternchen/MH-Z-CO2-Sensors
synced 2025-03-15 14:48:55 +00:00
104 lines
2.2 KiB
C++
104 lines
2.2 KiB
C++
/* MHZ library
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By Tobias Schürg
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*/
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#include "MHZ.h"
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MHZ:: MHZ(uint8_t rxpin, uint8_t txpin, uint8_t pwmpin, uint8_t type)
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: co2Serial(rxpin, txpin)
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{
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_rxpin = rxpin;
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_txpin = txpin;
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_pwmpin = pwmpin;
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_type = type;
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co2Serial.begin(9600);
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}
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int MHZ::readCO2UART() {
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Serial.println("-- read CO2 uart ---");
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byte cmd[9] = {0xFF, 0x01, 0x86, 0x00, 0x00, 0x00, 0x00, 0x00, 0x79};
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byte response[9]; // for answer
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Serial.println("Sending CO2 request...");
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co2Serial.write(cmd, 9); //request PPM CO2
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// clear the buffer
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memset(response, 0, 9);
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int i = 0;
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while (co2Serial.available() == 0) {
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// Serial.print("Waiting for response ");
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// Serial.print(i);
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// Serial.println(" s");
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delay(1000);
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i++;
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}
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if (co2Serial.available() > 0) {
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co2Serial.readBytes(response, 9);
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}
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// print out the response in hexa
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for (int i = 0; i < 9; i++) {
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Serial.print(String(response[i], HEX));
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Serial.print(" ");
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}
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Serial.println("");
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// checksum
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byte check = getCheckSum(response);
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if (response[8] != check) {
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Serial.println("Checksum not OK!");
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Serial.print("Received: ");
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Serial.println(response[8]);
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Serial.print("Should be: ");
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Serial.println(check);
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}
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// ppm
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int ppm_uart = 256 * (int)response[2] + response[3];
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Serial.print("PPM UART: ");
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Serial.println(ppm_uart);
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// temp
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byte temp = response[4] - 40;
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Serial.print("Temperature? ");
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Serial.println(temp);
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// status
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byte status = response[5];
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Serial.print("Status? ");
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Serial.println(status);
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if (status == 0x40) {
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Serial.println("Status OK");
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}
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return ppm_uart;
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}
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byte MHZ::getCheckSum(byte *packet) {
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Serial.println("-- get checksum ---");
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byte i;
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unsigned char checksum = 0;
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for (i = 1; i < 8; i++) {
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checksum += packet[i];
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}
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checksum = 0xff - checksum;
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checksum += 1;
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return checksum;
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}
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int MHZ::readCO2PWM() {
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Serial.println("-- read CO2 pwm ---");
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unsigned long th, tl, ppm_pwm = 0;
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do {
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Serial.print(".");
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th = pulseIn(_pwmpin, HIGH, 1004000) / 1000;
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tl = 1004 - th;
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ppm_pwm = 5000 * (th - 2) / (th + tl - 4);
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} while (th == 0);
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Serial.print("PPM PWM: ");
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Serial.println(ppm_pwm);
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return ppm_pwm;
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}
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