Hello, I'm working on a project that requires measuring humidity, temperature, and air pressure and writing the data to an SD card.
I'm new to Arduino, so please forgive me if I make any mistakes or my code looks sloppy.
The data from the BMP280 sensor is incorrect, displaying negative pressures and quite warm temperatures (186 degrees Celsius!).
When I run the example code from the Adafruit BMP280 library on the same circuit, it produces correct readings, leading me to believe that this is a software issue.
Could it be due to having to share the SCK, MISO, and MOSI pins?
Thank you ahead of time!
#include <SD.h> //Library for SD card reader.
#include "DHT.h" //Libraries for the DHT22 sensor.
#define DHTPIN 2
#define DHTTYPE DHT22
DHT dht(DHTPIN, DHTTYPE);
#include <Wire.h> //Libraries for the BMP280 sensor.
#include <SPI.h>
#include <Adafruit_BMP280.h>
#define BMP_SCK (13)
#define BMP_MISO (12)
#define BMP_MOSI (11)
#define BMP_CS (5) //BMP280 CS pin.
Adafruit_BMP280 bmp(BMP_CS, BMP_MOSI, BMP_MISO, BMP_SCK);
File myFile;
const int chipSelect = 4; //SD card reader CS pin.
void setup()
{
pinMode(7, OUTPUT); //For LED and buzzer.
Serial.begin(9600);
digitalWrite(7, LOW);
Serial.println(F("BMP280 test"));
if (!bmp.begin(5)) {
Serial.println(F("Could not find a valid BMP280 sensor, check wiring or "
"try a different address!"));
while (1) delay(10);
}
/* Default settings from datasheet. */
bmp.setSampling(Adafruit_BMP280::MODE_NORMAL, /* Operating Mode. */
Adafruit_BMP280::SAMPLING_X2, /* Temp. oversampling */
Adafruit_BMP280::SAMPLING_X16, /* Pressure oversampling */
Adafruit_BMP280::FILTER_X16, /* Filtering. */
Adafruit_BMP280::STANDBY_MS_500); /* Standby time. */
Serial.print("Initializing SD card...");
// Note that even if it's not used as the CS pin, the hardware SS pin
// (10 on most Arduino boards, 53 on the Mega) must be left as an output
// or the SD library functions will not work.
pinMode(10, OUTPUT);
dht.begin();
if (!SD.begin(4)) {
Serial.println("initialization failed!");
digitalWrite(7, HIGH);
return;
}
Serial.println("initialization done.");
// open the file. note that only one file can be open at a time,
// so you have to close this one before opening another.
myFile = SD.open("humi.txt", FILE_WRITE);
// if the file opened okay, write to it:
if (myFile) {
Serial.print("Writing to humi.txt...");
float humi = dht.readHumidity();
// read temperature as Celsius
float tempC = dht.readTemperature();
// read temperature as Fahrenheit
float tempF = dht.readTemperature(true);
// check if any reads failed
if (isnan(humi) || isnan(tempC) || isnan(tempF)) {
Serial.println("Failed to read from DHT sensor!");
digitalWrite(7, HIGH);
} else {
myFile.print("Humidity: "); //Write data from DHT22 sensor.
myFile.print(humi);
myFile.print("%");
myFile.print(" | ");
myFile.print("Temperature: ");
myFile.print(tempC);
myFile.print("°C ~ ");
myFile.print(tempF);
myFile.println("°F");
delay(1000);
myFile.print(F("Temperature = ")); //Write data from BMP280
myFile.print(bmp.readTemperature());
myFile.println(" *C");
myFile.print(F("Pressure = "));
myFile.print(bmp.readPressure());
myFile.println(" Pa");
myFile.print(F("Approx altitude = "));
myFile.print(bmp.readAltitude(1013.25)); /* Adjusted to local forecast! */
myFile.println(" m");
myFile.println();
}
// close the file:
myFile.close();
Serial.println("done.");
} else {
// if the file didn't open, print an error:
Serial.println("error opening humi.txt");
}
// re-open the file for reading:
myFile = SD.open("humi.txt");
if (myFile) {
Serial.println("humi.txt:");
// read from the file until there's nothing else in it:
while (myFile.available()) {
Serial.write(myFile.read());
}
// close the file:
myFile.close();
} else {
// if the file didn't open, print an error:
Serial.println("error opening humi.txt");
}
}
void loop() //Flashes LED and turns buzzer on/off.
{
digitalWrite(7, HIGH);
delay(1000);
digitalWrite(7, LOW);
delay(1000);
}
