29 917
modifications
Modifications
Sauter à la navigation
Sauter à la recherche
Ligne 56 :
Ligne 56 : + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
→High resolution reading
== Testing the sensor ==
== Testing the sensor ==
In the both case show here under, the measured temperature would be identical.
{{ambox|text=However, if your project does need a high resolution analog reads then it may be appropriate to explore the "High Resolution Reading" example.}}
By default, the Arduino's {{fname|analogRead()}} use a 10 bit coding. So the range of possible value return by {{fname|analogRead()}} is 0 to 1024 (for 0 to 3.3v). This means that the accuracy of reading is 3.3 / 1024 = 0.0032 Volts, so 3.2 mV.
As the M0 does have an ADC (''Analog-to-Digital Converter'') with a precision of 12 bits, we could also use the {{fname|analogReadResolution( 12 )}} to upgrade the {{fname|analogRead()}} resolution to 12 bits. In such case, the range of possible value return by {{fname|analogRead()}} is 0 to 4095 (for 0 to 3.3v). As we have a real 12bit ADC, we can rely on that accuracy (it is not a 10 bits ADC storing the data into a 12 bits integer).
with 12bits we have an reading accuracy of 3.3 / 4095 = 0.000805 Volts, so 0.805 mV.
=== Low resolution reading ===
<syntaxhighlight lang="c">
// where is wired the TMP36
const int temperaturePin = A3; // analogue input
// Executed once when starting the microcontroler
void setup() {
// start serial connexion with the computer
Serial.begin(9600);
}
// Executed again and again
void loop() {
// read the voltage of TMP36
float voltage = getVoltage(temperaturePin);
Serial.print( "Voltage : " );
Serial.print( voltage );
Serial.println( " Volts" );
// convert voltage to temperature
// Degrees = (voltage - 500mV) multiplied by 100
float temperature = (voltage - .5) *100;
Serial.print( "Temperature: " );
Serial.print(temperature);
Serial.println( " °C" );
Serial.println( " " );
delay(1000); // wait 1 second
}
/*
* getVoltage() - return the voltage of an analog pin
*/
float getVoltage(int pin){
// AS the sketch does not call the analogReadResolution()
// function to change the analog reading resolution
// THEN Arduino use the defaut 12 bits resolution!
// Under 12 bits resolution, the analogRead() returns
// a value between 0 & 1024.
//
// Convert digital value between 0 & 1024 to
// voltage between 0 & 3.3 volts.
// (each unit equal 3.3 / 1024 = 3.2 millivolts)
return (analogRead(pin) * .0032);
}
</syntaxhighlight>
Once the sketch uploaded to the board, you can start the Serial Monitor
[[Fichier:ENG-CANSAT-BMP280-04.png]]
Which produce the following result on the Serial Monitor
[[Fichier:ENG-CANSAT-TMP36-60.png|640px]]
{{ENG-CANSAT-TRAILER}}
=== High resolution reading ===
<syntaxhighlight lang="c">
// where is wired the TMP36
const int temperaturePin = A3; // analogue input
// Executed once when starting the microcontroler
void setup() {
// start serial connexion with the computer
Serial.begin(9600);
// Upgrade the ADC resolution from 10 to 12 bits.
analogReadResolution( 12 );
}
// Executed again and again
void loop() {
// read the voltage of TMP36
float voltage = getVoltage(temperaturePin);
Serial.print( "Voltage : " );
Serial.print( voltage );
Serial.println( " Volts" );
// convert voltage to temperature
// Degrees = (voltage - 500mV) multiplied by 100
float temperature = (voltage - .5) *100;
Serial.print( "Temperature: " );
Serial.print(temperature);
Serial.println( " °C" );
Serial.println( " " );
delay(1000); // wait 1 second
}
/*
* getVoltage() - return the voltage of an analog pin
*/
float getVoltage(int pin){
// Convert digital value between 0 & 4095 to
// voltage between 0 & 3.3 volts.
// (each unit equal 3.3 / 4095 = 0.805 millivolts)
return (analogRead(pin) * .000805);
}
</syntaxhighlight>
Once the sketch uploaded to the board, you can start the Serial Monitor
[[Fichier:ENG-CANSAT-BMP280-04.png]]
Which produce the following result on the Serial Monitor
[[Fichier:ENG-CANSAT-TMP36-70.png|640px]]
{{ENG-CANSAT-TRAILER}}
{{ENG-CANSAT-TRAILER}}