Let’s check the device first. I had to wire the accelerometer, the Zigbee Module and the battery to the Arduino Fio. Let’s look at some schematics made using the nice open-source tool named Fritzing.
At first, you have to know the Arduino Fio has (also) been designed to be programmed wirelessly via the XBee module. It is really interesting but we also have to understand how we can program it wired to our computer, which is the most usual case. Arduino Fio USB connector cannot be used to program it. I guess you are now totally frightened by this, but of course, we have another way of programming it: our precious FTDI break out adapter.
Let’s see how the connection goes.
Arduino Fio’s back shows 6 pins grouped under the name FTDI.
Basically, our small FTDI breakout is a USB to RS232 serial interface.
It means we have to connect the FTDI board to the Arduino Fio and then connect th FTDI board to our computer with an USB cable in order to be able to program the Arduino Fio via the Arduino IDE.
I used to make this without soldering the header pins on the Fio side in order to save place if I have to put in small boxes. Check the FTDI board orientation: Gnd is the first connector at the top on the Fio side: don’t make a mistake here.
Choose the Arduino Fio in your board list in the IDE, then choose the FTDI board listed under the name /dev/tty.usbserial-A601EPM3 on OSX
<image here> Boards list Choose the serial port used for programming the Arduino board <image here>
Now, the basic workflow is still the same as in the first article of this series. You can code, and upload your code into Arduino Fio. Let’s next check the Accelerometer part.
ADXL345 accelerometer supports 2 differents serial communication protocol:
I used I2C and ADXL345 nice library: https://code.google.com/p/adxl345driver/. You can find a lot of explanation about serial communications in my book.
The accelerometer in this project is used for two purposes:
I inspired myself from the project of bildr.org here: http://bildr.org/2011/03/adxl345-arduino/
I modified some parts as you’ll see later in this article.
Let’s see the wiring of the accelerometer using I2C 2-wires circuit.
<image here> ADXL345 accelerometer wired to the Arduino Fio
I decided to solder my accelerometer to a small board in order to be able to wire it to the Arduino more freely.
Here are some pictures about that:
<image here> small soldering setup compared to protodeck project ;)
<image here> Useful small boards with connector connected 3 by 3 on rows
<image here> ADXL345 Accelerometer on which I soldered a small header
<image here> The ADXL345 soldered on the small board
<image here> Prepared 5 wires for ADXL345 soldering to Arduino Fio
<image here> ADXL345 wired to the Arduino Fio
The use of flexible a bit too long wires is adviced here. Indeed, I didn’t know precisely at this moment how I could wire the whole stuff in the box.. so having some length spare could help.
This is a bit tip here: I knew I needed only 4 wires, the CS pin of the accelerometer being wired to the VCC one, but I prepared 5. Indeed, while wiring/soldering, if something goes wrong on a wire, you can use a spare one.