measurement_co2_by_S300L_for_arduino_uno_r3.ino

/* Measurement CO2 by S-300L-3V for Arduino UNO R3 */
/* Output >>
Ready
862
866
871
875
877
*/

#include <SoftwareSerial.h>
SoftwareSerial SerialUART(6, 7); // RX, TX

/* by S-300L: http://doc.switch-science.com/datasheets/ELT/User+Guide+for+U-ART+command+for+Low-Power+ver160719+cdg.pdf */
uint16_t CO2ppm() {
  while (!SerialUART.available()); /* wait max 3 seconds by spec (TODO: Timeout) */
  String buf = SerialUART.readStringUntil('\n'); /* separete char by spec */
  int pos = buf.lastIndexOf(" ppm"); /* Avoiding garbage in buffer */
  String v = buf.substring(pos - 6, pos);
  return v.toInt();
}

void setup() {
  Serial.begin(115200);
  SerialUART.begin(38400);
  Serial.println("Ready");
}

void loop() {
  uint16_t ppm = CO2ppm();
  Serial.println(ppm);
  delay(5000);
}