Initial commit

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Tobias Schürg 2018-04-22 11:36:51 +02:00
commit 405515f61c
4 changed files with 125 additions and 0 deletions

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.gitattributes vendored Normal file
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# Auto detect text files and perform LF normalization
* text=auto

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LICENSE Normal file
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MIT License
Copyright (c) 2018 Tobias Schürg
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

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README.md Normal file
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# MH-Z19B CO2 Module

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mhz19-2.ino Normal file
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#include <SoftwareSerial.h>
SoftwareSerial co2Serial(7, 6); // define MH-Z19 RX TX
unsigned long startTime = millis();
void setup() {
Serial.begin(9600);
co2Serial.begin(9600);
pinMode(9, INPUT);
}
void loop() {
Serial.println("------------------------------");
Serial.print("Time from start: ");
Serial.print((millis() - startTime) / 1000);
Serial.println(" s");
int ppm_uart = readCO2UART();
int ppm_pwm = readCO2PWM();
delay(5000);
}
int readCO2UART() {
byte cmd[9] = {0xFF, 0x01, 0x86, 0x00, 0x00, 0x00, 0x00, 0x00, 0x79};
byte response[9]; // for answer
Serial.println("Sending CO2 request...");
co2Serial.write(cmd, 9); //request PPM CO2
// clear the buffer
memset(response, 0, 9);
int i = 0;
while (co2Serial.available() == 0) {
// Serial.print("Waiting for response ");
// Serial.print(i);
// Serial.println(" s");
delay(1000);
i++;
}
if (co2Serial.available() > 0) {
co2Serial.readBytes(response, 9);
}
// print out the response in hexa
for (int i = 0; i < 9; i++) {
Serial.print(String(response[i], HEX));
Serial.print(" ");
}
Serial.println("");
// checksum
byte check = getCheckSum(response);
if (response[8] != check) {
Serial.println("Checksum not OK!");
Serial.print("Received: ");
Serial.println(response[8]);
Serial.print("Should be: ");
Serial.println(check);
}
// ppm
int ppm_uart = 256 * (int)response[2] + response[3];
Serial.print("PPM UART: ");
Serial.println(ppm_uart);
// temp
byte temp = response[4] - 40;
Serial.print("Temperature? ");
Serial.println(temp);
// status
byte status = response[5];
Serial.print("Status? ");
Serial.println(status);
if (status == 0x40) {
Serial.println("Status OK");
}
return ppm_uart;
}
byte getCheckSum(char *packet) {
byte i;
unsigned char checksum = 0;
for (i = 1; i < 8; i++) {
checksum += packet[i];
}
checksum = 0xff - checksum;
checksum += 1;
return checksum;
}
int readCO2PWM() {
unsigned long th, tl, ppm_pwm = 0;
do {
th = pulseIn(9, HIGH, 1004000) / 1000;
tl = 1004 - th;
ppm_pwm = 5000 * (th - 2) / (th + tl - 4);
} while (th == 0);
Serial.print("PPM PWM: ");
Serial.println(ppm_pwm);
return ppm_pwm;
}