Pitch and Roll Accelerometer

[brookemilligan]

Hi all,
I have been working on building a swinging Pendulum and I have decided to add an accelerometer and SDcard to collect the data from the accelerometer but I'm having trouble with how to write my pitch angle onto the SDcard and the serial monitor.

Here's my code. If anyone has any ideas that would be amazing. The accelerometer I'm using is the MMA8452Q with an Arduino Uno.

#include <math.h>
#include <SPI.h>
#include <SD.h>
#include <Wire.h> // Must include Wire library for I2C
#include "SparkFun_MMA8452Q.h" // Click here to get the library: http://librarymanager/All#SparkFun_MMA8452Q

MMA8452Q accel; // create instance of the MMA8452 class

const int chipSelect = 4; // pin 4 for Uno

void setup() {
// Open serial communications and wait for port to open:
Serial.begin(9600);
while (!Serial) {
; // wait for serial port to connect. Needed for native USB port only
}
Serial.print("Initializing SD card...");

// see if the card is present and can be initialized:
if (!SD.begin(chipSelect)) {
Serial.println("Card failed, or not present");
// don't do anything more:
while (1);
}
Serial.println("card initialized.");

Wire.begin();
if (accel.begin() == false) {
Serial.println("Not Connected. Please check connections and read the hookup guide.");
while (1);
}
}

void loop() {
if (accel.available()) {
Serial.print(accel.getCalculatedX(), 3);
Serial.print("\t");
Serial.print(accel.getCalculatedY(), 3);
Serial.print("\t");
Serial.print(accel.getCalculatedZ(), 3);
Serial.println();
}
File dataFile = SD.open("datalog.txt", FILE_WRITE);
if (dataFile) {
if (accel.available()) {
dataFile.print(accel.getCalculatedX(), 3);
dataFile.print("\t");
dataFile.print(accel.getCalculatedY(), 3);
dataFile.print("\t");
dataFile.print(accel.getCalculatedZ(), 3);
dataFile.print("\t");
dataFile.println();
}
else {
Serial.print("accel not available");
}
dataFile.close();
// print to the serial port too:
}
// if the file isn't open, pop up an error:
else {
Serial.println("error opening datalog.txt");
}
}
void checkTilt() {
if (accel.available() == true) {
accel.read();
float aX = float(accel.x);
float aY = float(accel.y);
float aZ = float(accel.z);
int pitch = atan2(-aX, aZ) * 180 / M_PI; // rotation on Y axis
int roll = atan2(-aY, aZ) * 180 / M_PI; // rotation on X axis
/*
If accelerometer is level, pitch and roll will both be 0
Pitch: Tilted Up = 1 to 180, Tilted Down = -1 to -180
Roll: Tilted Right = 1 to 180, Tilted Left = -1 to -180
*/
}
}

[anon73444976]

What would be amazing is that a first time poster actually read the posting guidelines.

I have yet to be amazed

[jremington]

Please edit your post to add code tags.

It may not matter for your application, but the formulas for pitch and roll are not correct. Here are some correct ones.

File open and close operations are very slow. To write data to the SD card quickly, open the file once in setup(), not in loop(). Close the file only when you are done collecting data. Also, do not use Serial.print() at the same time, or use a much higher baud rate than 9600.