Adafruit BMP280 + Micro SD Card Reader for Altimeter Data Logger

1#include <Wire.h>
2#include <SPI.h>
3#include <SD.h>
4#include <Adafruit_BMP280.h>
5
6Adafruit_BMP280 bmp;
7
8float newAlt;
9float alt;
10float origAlt;
11float temp;
12
13const int chipSelect = 10; // Change if your CS pin is different
14unsigned long lastLogTime = 0;
15
16void setup() {
17  Serial.begin(9600);
18  while (!Serial);  // wait for serial on some boards
19
20  Serial.println("Initializing BMP280...");
21  if (!bmp.begin(0x76, 0x60)) {
22    Serial.println("Error: BMP280 not found at 0x76");
23    while (1);  // halt
24  }
25
26  bmp.setSampling(Adafruit_BMP280::MODE_NORMAL,
27                  Adafruit_BMP280::SAMPLING_X2,
28                  Adafruit_BMP280::SAMPLING_X16,
29                  Adafruit_BMP280::FILTER_X16,
30                  Adafruit_BMP280::STANDBY_MS_500);
31
32  origAlt = bmp.readAltitude(1013.25); // baseline altitude
33
34  Serial.println("Initializing SD card...");
35  if (!SD.begin(chipSelect)) {
36    Serial.println("Error: SD init failed");
37    while (1);
38  }
39
40  // Create or clear the log file at start
41  File logFile = SD.open("altlog.txt", FILE_WRITE);
42  if (logFile) {
43    logFile.println("Altitude(ft)");
44    logFile.close();
45    Serial.println("SD card ready, logging started.");
46  } else {
47    Serial.println("Error: Can't create log file");
48  }
49}
50
51void loop() {
52  temp = bmp.readTemperature();
53  newAlt = bmp.readAltitude(1013.25);
54
55  if (newAlt > alt) {
56    alt = newAlt;
57  }
58
59  float feet = (alt - origAlt) * 3.281;
60
61  // Log altitude to SD every second
62  if (millis() - lastLogTime >= 1000) {
63    lastLogTime = millis();
64
65    File logFile = SD.open("altlog.txt", FILE_WRITE);
66    if (logFile) {
67      logFile.println(feet, 2);
68      logFile.close();
69    } else {
70      Serial.println("Error: Can't open altlog.txt for writing");
71    }
72  }
73}