I2C on Cubieboard with Lubuntu

May 19, 2014 (Last Modified: May 19, 2014)

I2C bus is used by many integrated circuits and is simple to implement. Any microcontroller can communicate with I2C devices even if it has no special I2C interface so I wanted to enable I2C also in my Cubieboard2 to get direct access to sensors.

Following commands are useful for I2C interface:

i2cdetect (used to detect slaves address in the bus)
i2cdump (used get a range of values)
i2cget (used to get a value)
i2cset (used to set a value)

You can install them from one package:

sudo apt-get install i2c-tools

To check your connected I2C devices run:

 sudo i2cdetect -y -r 1

I followed the how-to by cubieboard to enable I2C port on my lubuntu cubieboard2:

sudo mount /dev/nanda /mnt
cd /mnt
sudo bin2fex script.bin script.fex
sudo vi script.fex

I changed only i2c (twi)- I selected the one that was already configured to PB18/19 twi1_para. Pin #6 is SCL and pin #7 is SDA (U15 – the pin array near the USB-Ports). Refer to pin definition (or this PDF) :

<td style="border: 1px solid #cccccc; margin: 0px; padding: 0.3em 0.5em; vertical-align: top;">
  PG0 (CSI1-PCLK/SDC1-CMD)
</td>

<td style="border: 1px solid #cccccc; margin: 0px; padding: 0.3em 0.5em; vertical-align: top;">
  <b>6</b>
</td>

<td style="border: 1px solid #cccccc; margin: 0px; padding: 0.3em 0.5em; vertical-align: top;">
  <b>PB18 (TWI1-SCK)</b>
</td>

<td style="border: 1px solid #cccccc; margin: 0px; padding: 0.3em 0.5em; vertical-align: top;">
  <b>PB19 (TWI1-SDA)</b>
</td>

<td style="border: 1px solid #cccccc; margin: 0px; padding: 0.3em 0.5em; vertical-align: top;">
  8
</td>

<td style="border: 1px solid #cccccc; margin: 0px; padding: 0.3em 0.5em; vertical-align: top;">
  PG3 (CSI1-VSYNC/SDC1-D1)
</td>

[twi1_para]
twi1_used = 1
twi1_scl = port:PB18<2><default><default><default>
twi1_sda = port:PB19<2><default><default><default>

Save the file and convert it back to script.bin:

sudo fex2bin script.fex script.bin
sudo reboot

Connect your I2C device (BMP085 sensor in my case) and now test the I2C interface.

sudo i2cdetect -r 1

I have connected BMP085 that is preconfigured with address 0x77 detected by i2cdetect.
In my next post, you can see how I programmed cubieboard to get data from the BMP085 barometric pressure sensor –> cubieboard-with-bmp085-barometer
In Cubian the /dev/i2c/1 is already preconfigured (cubian follow this guide http://wp.applesandoranges.eu/?p=48)
Other usefull links: