mma8451 - Accel experimental software

Simple code example for Adafruit MMA8452 3-axis Accelerometer.

This is a very basic python library for mma8451 accelerometer. The library was tested on Raspberry pi model 2A and model 3 connected to the Freescale(c) MMA8451 3-axis accelerometer sensor, purchased from Adafruit(c). This is the Adafruit page regarding our device> https://www.adafruit.com/?q=mma8451&

Dependencies and related readings:

1. https://learn.adafruit.com/adafruit-16-channel-servo-driver-with-raspberry-pi/configuring-your-pi-for-i2c A brief guide on How to Configure Your Pi for I2C

2. http://www.nxp.com/doc/MMA8451Q The MMA8451 Data sheet: Technical data

3. https://www.nxp.com/docs/en/application-note/AN4076.pdf Data Manipulation and Basic Settings of the MMA8451, 2, 3Q

Initial Preparation

This section explains how to setup the whole things to test your MMA8451 device on a Raspberry Pi

Basic environment Preparation

• Grab the following material:

  1. One Raspberry Pi (which could be any model)
  2. One Power supply for Raspberry Pi
  3. One SD card or MicroSD card (depending on your RPi model) preferably a class 10
  4. One HDMI monitor
  5. One USB Mouse
  6. One USB Keyboard
  7. One MMA85451 3-axis accelerometer sensor

• Also have available... 8. A good internet connection (to access the internet) 9. A LAN switch (to connect you RPi to the internet) and a RJ45 UTP/STP LAN straight Cable (patch cord) 10. Another PC (either Windows, Linux or Mac will be OK) 11. Enough patience and Spirit of Adventure :)

Raspberry Pi preparation and setup

• From you PC, download a Raspbian GNU/Linux 8 (jessie) for your RPi. See download page at: https://www.raspberrypi.org/downloads/
• Transfer/Copy the Operating System (Raspbian GNU/Linux 8 - jessie) into the SD/MicroSD Card. (see instruction at: https://www.raspberrypi.org/documentation/installation/installing-images/)
  1. Instruction on how to install RPi OS from Windows(R) can be found at: https://www.raspberrypi.org/documentation/installation/installing-images/windows.md
  2. Instruction on how to install RPi OS from Linux can be found at: https://www.raspberrypi.org/documentation/installation/installing-images/linux.md

Once you have transferred/copied the Raspblian into the SD/MicroSD

• Safely dismount the SD/MicroSD Card from your PC
• Stick the SD/MicroSD Card into your RPi
• Connect the HDMI cable of your monitor to rhe HDMI connetor of your RPi
• Connect the USB keyboard to one of the USB connectors available on your RPi
• Connect the USB mouse to ne of the USB connectors available on your RPi
• Connect your RPi to you LAN switch using the LAN Cable (patch cord)
• Power up your RPi by connecting the microUSB connector of the Power Supply to your RPi
• You can watch the startup process of your RPi on the screen.

When the startup procedure is completed you can begin configure you RPi as described here below.

• On our RPi screen, open a terminal window

• Run the Raspberry Pi configuration tool raspi-config to apply some basic RPi configuration, at least those mentioned below are recommended (for more information, please consult: https://www.raspberrypi.org/documentation/configuration/raspi-config.md)

  1. Expand Filesystem : to Ensures that all of the SD card storage is available to the OS
  2. Change User Password : to change password for the default user (pi)
  3. Advanced Options => A6 I2C : to enable automatic loading of I2C kernel module
  4. Advanced Options => A4 SSH : to enable remote command line access to your Pi using SSH ''' sudo raspi-config # Run raspi-config sudo reboot # after raspi-config terminates, reboot your RPi to allow changes to take effect '''

• Run rpi-update to update your RPi firmware and reboot to allow all changes to take effect.

  sudo rpi-update
  sudo reboot
  

• Update all packages and eventually newer kernel version (more info at: https://www.raspberrypi.org/documentation/raspbian/updating.md)

  sudo apt-get update
  sudo apt-get upgrade
  

  Please note that the above command takes some time to complete, since it access the internet to download and install ann the needed software.

• Install the following packages via shell command and reboot you RPi

  sudo apt-get install build-essential python-dev python-smbus python-pip git
  sudo apt-get install i2c-tools
  sudo reboot
  

• Update your RPi firmware (useful information can be found at: https://www.raspberrypi.org/forums/viewtopic.php?t=58963)

  sudo rpi-update 
  

  Please note that the above command takes some time to complete, since it access the internet to download and install ann the needed software.

Software installation

This section will guide you to install the software and run it

Preliminary set up

In order to allow the MMA8451 software to run as a regular user, for example user pi (or any other user you might prefer), it is important that the software can access some of the system device file appropriately.

In order to do that, please follow these instructions.

• The file /sys/module/i2c_bcm2708/parameters/combined must be Read/Write for all users

• The file /sys/module/i2c_bcm2708/parameters/combined must contain Y (upper-case 'Y') The above can be achieved by manually setting the requirements via shell command, as follows:

  sudo chmod 666 /sys/module/i2c_bcm2708/parameters/combined
  sudo echo -n 1 > /sys/module/i2c_bcm2708/parameters/combined
  modprobe i2c_bcm2708
  

Or by adding the following chunk of code to the file /etc/rc.local

```
if [ -e /sys/module/i2c_bcm2708/parameters/combined ]; then
    chmod 666 /sys/module/i2c_bcm2708/parameters/combined >> /dev/null
    echo -n 1 > /sys/module/i2c_bcm2708/parameters/combined
fi
```

So that the setting will be applied automatically, every your RPi is rebooted.

MAA8451 Software installation

The installation of the MMA8451 Experimental software is quite easy:

• Download the software from gitub at https://github.com/massixone/mma8451

  git clone https://github.com/massixone/mma8451
  cd mma8451
  

• Run the software

  ./accel.py
  

Finally, Have Fun!