Der ADXL345 ist ein stromsparender (40µA beim Messen, 0,1µA im StandBy) 3-Achsen Beschleunigungssensor, mit einer Auflösung von 13-Bit ist er sehr genau (4mg/LSB).
Die Messadten lassen sich über SPI (3 oder 4 Wire Betrieb) oder I2C auslesen.
Der Sensor enthält zahlreiche eingebaute Funktionen, wie z.B. Freie Fall Erkennung, Überschreitung eines Voreingestellten Messwertes.
Technische Daten:
- 2.0-3.6VDC Supply Voltage
- Ultra Low Power: 40uA in measurement mode, 0.1uA in standby@ 2.5V
- Tap/Double Tap Detection
- Free-Fall Detection
- SPI and I2C interfaces
#include <Wire.h> #define DEVICE (0x53) //ADXL345 device address #define TO_READ (6) //num of bytes we are going to read each time (two bytes for each axis) byte buff[TO_READ] ; //6 bytes buffer for saving data read from the device char str[512]; //string buffer to transform data before sending it to the serial port double g = 9.806; int time; void setup() { Wire.begin(); // join i2c bus (address optional for master) Serial.begin(9600); // start serial for output //Turning on the ADXL345 writeTo(DEVICE, 0x2D, 0); writeTo(DEVICE, 0x2D, 16); writeTo(DEVICE, 0x2D, 8); } void loop() { // Serial.println('Neue Messung'); // while(true){ int regAddress = 0x32; //first axis-acceleration-data register on the ADXL345 int x, y, z; double ax, ay , az; readFrom(DEVICE, regAddress, TO_READ, buff); //read the acceleration data from the ADXL345 //each axis reading comes in 10 bit resolution, ie 2 bytes. Least Significat Byte first!! //thus we are converting both bytes in to one int x = (((int)buff[1]) << 8) | buff[0]; y = (((int)buff[3])<< 8) | buff[2]; z = (((int)buff[5]) << 8) | buff[4]; time = millis(); time = time * 0.001; //we send the x y z values as a string to the serial port sprintf(str, "%d %d %d", x, y, z); Serial.print(str); Serial.print(" "); Serial.println(time); //It appears that delay is needed in order not to clog the port delay(50); } //---------------- Functions //Writes val to address register on device void writeTo(int device, byte address, byte val) { Wire.beginTransmission(device); //start transmission to device Wire.write(address); // send register address Wire.write(val); // send value to write Wire.endTransmission(); //end transmission } //reads num bytes starting from address register on device in to buff array void readFrom(int device, byte address, int num, byte buff[]) { Wire.beginTransmission(device); //start transmission to device Wire.write(address); //sends address to read from Wire.endTransmission(); //end transmission Wire.beginTransmission(device); //start transmission to device Wire.requestFrom(device, num); // request 6 bytes from device int i = 0; while(Wire.available()) //device may send less than requested (abnormal) { buff[i] = Wire.read(); // receive a byte i++; } Wire.endTransmission(); //end transmission }
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