This module integrates the sensor MMA7455L (produced by Freescale), able to detect the movement on three axes, and then in every direction. The chip offers the possibility to select three different sensitivity (± 2g, ± 4g, ± 8g) and makes available, on an SPI bus and the I²C-Bus, the data detected by allowing a more easily read by a microcontroller. There are also two programmable interrupt lines to communicate a certain event, or to perform one or more actions when it detects a certain acceleration or when the module is stopped.
 |
|
| Figure 1. | Module that integretes MMA7455L Three Axis Digital Output Accelerometer. |
The accelerometer connections are carried out on a male strip pitch 2.54 mm, seven contacts, which allows the insertion in any dip socket, female strip or directly on the printed circuit. The module, powered with a DC voltage of 2.5 to 3.6 V, is suitable for be used in all systems that require the detection of movement, acceleration, such as an alarm systems for vehicle, laboratory analytical instruments, electrical equipment, machinery test and robots.
 |
|
| Figure 2. | The module has extremely compact dimensions (10×18×3,6mm). |
Before using this module is necessary to establish (through jumper J1) which must be the voltage applied to pin VIO (Digital Power for I/O pads), levels of the I / O interface must be the same of micro. If the voltage applied between the pin + and – of the module is the same as the interface device is necessary to close J1, while if it is different (for example because the micro operates at 5V) the jumper must be open and the line VIO must be connects to the same supply voltage of the microcontroller. The I²C-Bus module is assigned to 00111011. For more information on the chip MMA7455L consult the datasheet from the Internet site www.freescale.com.
 |
|
| Рисунок 3. | MMMA7455L Breakout Module Schematic Diagram. |
To show the operation of the module I made a little demo with Arduino.
The connection to the microcontroller is very simple and the pin-out allows you to insert the module in the 6-pin for the analog inputs (Figure 4). The low absorption permit to use the input pin A0 as level of communicationis (VIO) brought it to a high logic level (5V), while the pin A1 is set to 0, the mass for the MMA7455L.
The main supply voltage is provide from 3.3 V by Arduino (Figure 5).
 |
|
| Figure 4. | Arduino with connected MMA7455L breakout module. |
 |
|
| Figure 5. | Main supply voltage is provide from 3.3 V from Arduino Board. |
Thanks to the library Wire.h pin A4 and A5 are used to communicate directly with the module.
The communication is very simple thank the library MMA_7455.h developed by Moritz Kemper.
The software written in Processing By IAN allows you to immediately verify the correct operation of Freescale chip. A cube will rotate like the movements of the sensor.
Demonstration video
Downloads
MMA_7455.h and Wire.h libraries, exapmles, software - download
