Hi Arduino gurus!
I have an Arduino Uno setup with a CO2 monitor, with code that should output the CO2 values from the sensor.
However, when I upload the code and run the serial monitor outputs reverse question marks (as uploaded on the picture).
I know a lot of people have had the same issue, and I tried to implement the same solutions but nothing has worked. The baud value matches in Serial Monitor and the code.
Can you help me figuring out what is wrong? Below I have attached the code, pictures and hardware setup.
Best regards
Valdemar
#include <SoftwareSerial.h>
SoftwareSerial SerialCom(13, 12); // RX, TX
// analog interface
const int analogPin = A0;
// PWM interface
const int pwmPin = 9;
void setup() {
SerialCom.begin(9600);
pinMode(pwmPin, INPUT_PULLUP);
delay(180000); // preheat the CO2 sensor for 3 minutes
Serial.begin(115200);
Serial.println("Analog:,UART:,PWM:");
}
void loop() {
int ppm_analog = get_analog();
int ppm_uart = gas_concentration_uart();
int ppm_PWM = gas_concentration_PWM();
Serial.print(ppm_analog);
Serial.print(",");
Serial.print(ppm_uart);
Serial.print(",");
Serial.println(ppm_PWM);
delay(60000); // sleep for 1 minute
}
int get_analog() {
float v = analogRead(analogPin) * 5.0 / 1023.0;
int gas_concentration = int((v) * (5000/2));
return gas_concentration;
}
int gas_concentration_uart() {
byte addArray[] = {0xFF, 0x01, 0x86, 0x00, 0x00, 0x00, 0x00, 0x00, 0x79};
char dataValue[9];
SerialCom.write(addArray, 9);
SerialCom.readBytes(dataValue, 9);
int resHigh = (int) dataValue[2];
int resLow = (int) dataValue[3];
int ppm_uart = (resHigh*256)+resLow;
return ppm_uart;
}
int gas_concentration_PWM() {
while (digitalRead(pwmPin) == LOW) {};
long t0 = millis();
while (digitalRead(pwmPin) == HIGH) {};
long t1 = millis();
while (digitalRead(pwmPin) == LOW) {};
long t2 = millis();
long tH = t1-t0;
long tL = t2-t1;
long ppm = 5000L * (tH - 2) / (tH + tL - 4);
while (digitalRead(pwmPin) == HIGH) {};
delay(10);
return int(ppm);
}
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