User:Sarah Labianca/Notebook/Smyth Lab/2012/04/05
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Downloadsto be filled in with libraries, code, etc, later Building a force gaugeAbout the ADXL345 and ArduinoBackground reading on accelerometers. Our accelerometer of choice was the ADXL 345 from SparkFun Electronics. There are a bunch of code examples for the ADXL345, and the datasheet and quickstart guide were very helpful. The board we used to control and process data from the ADXL345 was an Arduino Uno R3. CircuitI connected the ADXL to the Arduino using a relatively simple circuit. I used the circuit setup from a bildr tutorial. The accelerometer came mounted on a breakout board, with holes where pins could go. I had to solder pins onto the breakout board
Development EnvironmentI wrote and uploaded my code to the Arduino and accelerometer using the Arduino 1.0 IDE on Ubuntu 11.04. Help for getting the integrated development environment running on Ubuntu can be found here. The language is very similar to C. To write code for the ADXL in Arduino 1.0, one needs to have a library containing a .cpp and a .h file. The library is inserted into the libraries folder in the Arduino 1.0 directory. Essentially, a library contains subroutines one may find useful in writing their code and helps a programmer interface with a device, without having to worry about all the details. I used an ADXL 345 library that I found on a bildr tutorial. Code<source lang ="c"> //Arduino 1.0+ Only! //Arduino 1.0+ Only!
ADXL345 adxl; //variable adxl is an instance of the ADXL345 library int x,y,z; float Gx, Gy, Gz; int count=0; void setup(){ Serial.begin(9600); adxl.powerOn(); adxl.setRangeSetting(2); //G sensing range from -2g to +2g //set activity/ inactivity thresholds (0-255) adxl.setActivityThreshold(75); //62.5mg per increment adxl.setInactivityThreshold(75); //62.5mg per increment adxl.setTimeInactivity(6); // how many seconds of no activity is inactive? //look of activity movement on this axes - 1 == on; 0 == off adxl.setActivityX(1); adxl.setActivityY(1); adxl.setActivityZ(1); //look of inactivity movement on this axes - 1 == on; 0 == off adxl.setInactivityX(1); adxl.setInactivityY(1); adxl.setInactivityZ(1); //setting all interupts to take place on int pin 1 //I had issues with int pin 2, was unable to reset it adxl.setInterruptMapping( ADXL345_INT_ACTIVITY_BIT, ADXL345_INT1_PIN ); adxl.setInterruptMapping( ADXL345_INT_INACTIVITY_BIT, ADXL345_INT1_PIN ); //register interupt actions - 1 == on; 0 == off adxl.setInterrupt( ADXL345_INT_ACTIVITY_BIT, 1); adxl.setInterrupt( ADXL345_INT_INACTIVITY_BIT, 1); }
//To see current register values of ADXL345 //printAllRegister(); Scale(); Output(); //getInterruptSource clears all triggered actions after returning value //so do not call again until you need to recheck for triggered actions byte interrupts = adxl.getInterruptSource();
//inactivity if(adxl.triggered(interrupts, ADXL345_INACTIVITY)){ Serial.println("inactivity"); PrintHeadings(); } //activity //if(adxl.triggered(interrupts, ADXL345_ACTIVITY)){ // Serial.println("activity"); //delay(500); // DetermineOffsets();
//} }
void Scale (void){ adxl.readAccel(&x, &y, &z); //CORRECTING FOR OFFSET OF ACCELEROMETER DUE TO POSITION x=x-12; y=y-18; z=z-245; //SCALING IN G'S //scale = total g range / 1024 //-2g to +2g = 4/1024 = 0.00390625, -4g to +4g = 8/1024 = 0.0078125 //-8g to +8g = 16/1024 = 0.015625, -16g to +16g = 32/1024 = 0.03125 Gx = x * 0.0039; Gy = y * 0.0039; Gz = z * 0.0039; } void Output(void){ PrintData(); } void PrintHeadings(void){ //if(count == 0){ Label(); // } //if (count<50){ //count = count++; //} //if (count == 50){ // count = 1; // Label(); //} } void Label (void){ Serial.print("X Raw"); Serial.print("\t"); Serial.print("Y Raw"); Serial.print("\t"); Serial.print("Z Raw"); Serial.print("\t"); Serial.print("X Scaled"); Serial.print("\t"); Serial.print("Y Scaled"); Serial.print("\t"); Serial.println("Z Scaled"); Serial.println(""); } void PrintData (void){ Serial.print(x); Serial.print("\t"); Serial.print(y); Serial.print("\t"); Serial.print(z); Serial.print("\t"); Serial.print(Gx,3); // Serial.print(" G"); Serial.print("\t"); Serial.print(Gy,3); // Serial.print(" G"); Serial.print("\t"); Serial.print(Gz,3); // Serial.println(" G"); Serial.println(""); }
//To Determine Offsets void DetermineOffsets(void){ int x,y,z; adxl.readAccel(&x, &y, &z); Serial.println(x); Serial.println(y); Serial.println(z); delay(3600); } </source>
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