Added a modified version which shows the CO2 measurements on a LCD.

This commit is contained in:
Tobias Schürg 2018-04-22 21:18:39 +02:00
parent 144b2ed588
commit 1c6c808c03

145
MH-Z19B-LCD/MH-Z19B.ino Normal file
View file

@ -0,0 +1,145 @@
#include <SoftwareSerial.h>
// include the library code:
#include <LiquidCrystal.h>
// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
SoftwareSerial co2Serial(7, 6); // define MH-Z19 RX TX
unsigned long startTime = millis();
void setup() {
Serial.begin(9600);
co2Serial.begin(9600);
pinMode(9, INPUT);
// set up the LCD's number of columns and rows:
lcd.begin(16, 2);
lcd.print("CO2 heating up");
lcd.setCursor(4, 1);
lcd.print("seconds left");
for (int seconds = 180; seconds > 0; seconds--) {
lcd.setCursor(0, 1);
lcd.print(" "); // clear timer
lcd.setCursor(0, 1);
lcd.print(seconds);
delay(1000);
}
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("CO2 Air Quality");
}
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();
// TODO: just clear second line?
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("CO2 Air Quality");
lcd.setCursor(0, 1);
lcd.print("PPM: ");
lcd.setCursor(5, 1);
lcd.print(ppm_pwm);
lcd.setCursor(10, 1);
lcd.print("|");
lcd.setCursor(12, 1);
lcd.print(ppm_uart);
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;
}