This is a library for using the MMA7455 accelerometer as a tilt sensor, with an Arduino, through I2C. A tilt sensor simply tells you which way the device is oriented (e.g. Y axis up). This library abstracts away all the messy detail of the accelerometer stuff.
It is based on the code from the Arduino website.
To use this library, simply paste MMA7455.h and MMA7455.ino into the same folder as your main .ino file. Then add the following line to the top of your code.
#include "MMA7455.h"
If you only want to use this device as a simple 3-axis (or fewer) tilt sensor, you only need to consider two functions. The other functions are included just in case.
First initialise the device, using the following function. The argument up is set to the orientation the device starts in, which is Y_POS, Y_NEG, X_POS, X_NEG, Z_POS or Z_NEG. For example, in the first photo above, the device is in the Z_POS position, because the positive z axis is pointing up. In the 2nd photo it's in the Z_NEG position.
int MMA7455_init(orientation up);
Similarly, to read what orientation the device is in after initialising in a known orientation, use the following function.
orientation MMA7455_orientation(void);
This function returns Y_POS, Y_NEG, X_POS, X_NEG, Z_POS, Z_NEG or NOT_SURE. This function looks for which axis is measuring acceleration of about 1 g-force. (More specifically, greater than THRESH g-force.) If no axis is measuring close to 1 g-force, or multiple are, then it returns NOT_SURE.
The default I2C address for this device is 0x1D. If you are having trouble communicating to the device, change the following line in MMA7455.h.
#define MMA7455_I2C_ADDRESS 0x1D
There is an example program included. This prints the new orientation through serial, whenever the orientation changes.
To use it, start the device in the Z_POS position (like the first photo above). Then run the code. Open the serial monitor and see what it printed as you rotate the device.