I'm using an Arduino Uno, 1.0.5 r2 version of the IDE with and ultrasonic HC-SR04 sensor for measuring a tank water level. I want to send the data obtained over internet using the official arduino GSM shield sending them on the plot.ly servers with their API using a GPRS connection. When I'm doing all the tasks I get inaccurate values as these:
When I use the only ping sensor without the GSM shield all works well getting good data. The same using a potentiometer + GSM shield + plot.ly.
The function I use for getting the distance is:
long distCalc() {
long durata, distanza;
digitalWrite(TRIG_PIN, LOW); // TRIG_PIN = pin 12
delayMicroseconds(2);
digitalWrite(TRIG_PIN, HIGH);
delayMicroseconds(10);
digitalWrite(TRIG_PIN, LOW);
durata = pulseIn(ECHO_PIN, HIGH); //ECHO_PIN = pin 11
distanza = durata / 29.1 / 2 ;
return distanza; // in uscita la distanza in [cm]
}
and the one for posting the data on plot.ly servers is (loop function):
void loop() {
long distanza;
distanza = distCalc(); //fase di calcolo distanza
Serial.print(distanza);
Serial.println("cm");
graph.plot(millis(), int(distanza), tokens[0]); //fase di invio su plot.ly
delay(20);
}
Could it be a software serial interrupt that hangs the pulseIn measurement? How could I avoid this?
