This I2C Block simply breaks out an I2C bus on the Intel® Edison while level shifting it from 1.8V to your sensors voltage. This a simple board that can snap into your Edison and be used right away. SparkFun Block for Intel® Edison - I2C
I2C Tools
I2C device detection and register dump tools. These tools rely on the "i2c-dev" kernel driver.
You will need to get acquainted with a set of tools called I2C Tools, for our purposes the most common tools we are going to use are:
i2cdetect
i2cdump
i2cget
i2cset
i2cdetect
It will help us list the i2c buses we have in our system and also show the addresses of the slaves connected to certain bus. Now go to your Edison and type i2cdetect -l , you should get an output similar to this:
On the first Column we can see the i2c-1 the leading number indicates the number of the bus, in this case the bus is 1;
Remember! Edison uses bus 0 and 6 if you are using the Edison Arduino Breakout Board, but if you are using Edison Breakout board or the Sparkfun Base Block the Bus 0 will be 1 and here comes the tricky part, because when using Edison in the Arduino Breakout Board a module will be loaded,preventing us to see the slaves addresses in the bus, for example run this command: i2cdetect -y -r 1 we will get:
In the case of the Edison+ Sparkfun Base block we are able to see the i2c addresses from the LCD Display (where RGB controller is 0x62 and LCD controller is 0x70) and the ADC block (address 0x48). For this reason from now on we might use Edison with the Sparkfun Base Block or the MiniBreakout Board, since they interface directly with the Edison's I2C pins, but this doesn't mean it is not possible to use the Arduino Breakout Board as we will see next, so keep reading!.
i2cdump
It will show us the content of a specific register in our device, the syntax is:i2cdump -y BUS ADDRESS b so go to your Edison and try to dump the registers from the RGB device of the Display. the command should be i2cdump -y 1 0x62 b and the result should look something like this:
Please from the above dump, can you determinate what is the value of register 0x04, 0x03, 0x02?, do you know to what those registers correspond to?, check the datasheet for the PC9633 RGB Controller
Answer: the value for those 3 register is 0x00, to read the the dump we use the numbers from the left and the top like if they were coordinates, the sum of those values is equal to the register you want to read. i.e, taking the blue cirles we have 0x00 + 0x04 = 0x04, so the register 0x04 has the value 0x00 (red circle).
Now for the question about what these registers represent, if you read datasheet you will find that they are PWM registers 0 to 3, PWMx — Individual brightness control registers these registers, and here it involves another protocol PWM which stands for Pulse width modulation (go check the protocols section). As color is a mix of Red, Green and Blue we can mix light by adjusting its brightnes and this registers do just that the control bright in a scale of 0 to 255 :)
To see the other available registers take a look to page 11 of the PC9633 RGB Controller that has the Grove display.
i2cset & i2cget
These guys are used to set or retrieve the value of a specific register in our i2c device, so lets go and initiate the RGB controller of our Display and set the color to white :), you already know to what registers we should write (you found them in your datasheet) to set the color.
Remember i told you it is not quite impossible to do this on the Edison + Arduino Breakout Board?;
Well before I tell you how we can do a workaround let's remember... what are the lines needed by a device so I2C protocol can do its job?
Vdd (Power)
GND (Ground)
SDA (Data Line)
SCL (Clock Line)
Now go and check the Intel® Edison Kit for Arduino* Hardware Guide page 7, we know that the Arduino SDA and SCL pins are connected to bus 1, and when you connect a device it doesn't show when you try to do an i2cdetect so what are alternatives do we have?
Answer: There are other pins that offer the SDA and SCL and those correspond to Bus 6 and these pins are the Arduino's A4 and A5 in our Arduino Break-out Board!.. so basically we can connect the cables from the LCD like this:
Arduino Pin
LCD I2C pin
5v
Vdd
GND
GND
A4
SDA
A5
SCL
Well in your Edison's command-line type each command and hit Enter :)
So, 0xFF (or 255 in decimal) is just the value we set using i2cset :) you can also check that by dumping the RGB controller and you should see something like this:
For Edison using the Sparkfun Base Block
root@edison:~# i2cdump -y 1 0x62 b
0 1 2 3 4 5 6 7 8 9 a b c d e f 0123456789abcdef
00: 00 20 ff ff ff 00 ff 00 ff e2 e4 e8 e0 XX XX XX . .......????XXX
10: 00 20 ff ff ff 00 ff 00 ff e2 e4 e8 e0 XX XX XX . .......????XXX
20: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XXXXXXXXXXXXXXXX
30: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XXXXXXXXXXXXXXXX
40: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XXXXXXXXXXXXXXXX
50: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XXXXXXXXXXXXXXXX
60: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XXXXXXXXXXXXXXXX
70: XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XXXXXXXXXXXXXXXX
80: 80 20 ff ff ff 00 ff 00 ff e2 e4 e8 e0 XX XX XX ? .......????XXX
90: 80 20 ff ff ff 00 ff 00 ff e2 e4 e8 e0 XX XX XX ? .......????XXX
a0: a0 20 ff ff ff 00 ff 00 ff e2 e4 e8 e0 XX XX XX ? .......????XXX
b0: a0 20 ff ff ff 00 ff 00 ff e2 e4 e8 e0 XX XX XX ? .......????XXX
c0: c0 20 ff ff ff 00 ff 00 ff e2 e4 e8 e0 XX XX XX ? .......????XXX
d0: c0 20 ff ff ff 00 ff 00 ff e2 e4 e8 e0 XX XX XX ? .......????XXX
e0: e0 20 ff ff ff 00 ff 00 ff e2 e4 e8 e0 XX XX XX ? .......????XXX
f0: e0 20 ff ff ff 00 ff 00 ff e2 e4 e8 e0 XX XX XX ? .......????XXX
See?, 0x04, 0x03, 0x02 now have 0xFF as their value, try setting the color to a solid Green
Answer: you don't need to re initiate the RGB controller, just set the RGB registers to the correct values, to set the color to Green, we need R=0, G=255, B=0. so we only need to do:
Talking to our I2C devices using I2CTools is cool, and makes you look interesting, but lets face it, this is not practical enough, and option could be to put everything in a shell script but we want to get further than that like writing our own module and for that, during this tranining, we will create our grown-ups c program, we really recommend reading the I2C Documentation in linux (we'll be taking base code snippet from there) and about i2c-dev library we will be using it to develop our C program.
First let's see if we have what we need in our Edison and install it if not. So type opkg list | grep i2c and lets find out if you have something similar to this:
Now from the list in my Edison we can see we have the option to install i2c-tools-dev - 3.1.1-r0 if it doesn't show in your Edison then you will have to configure some repositories to have access to them since the i2c-dev libraries are not available by default, so use vim/nano to review /etc/opkg/base-feeds.conf where you should have something like this:
If you don't have it please add those lines to your file, for further help or instructions you can visit AlexT's Galileo & Edison pages
Once you have done editing, save and close the file and run opkg update to start downloading the list of available packages from those repos. After that check again with opkg list | grep i2c and verify you have the option to install i2c-tools-dev - 3.1.1-r0
root@edison:~#opkgupdate
root@edison:~#opkginstalli2c-tools-devInstallingi2c-tools-dev (3.1.1-r0) on root. Downloadinghttp://iotdk.intel.com/repos/3.5/iotdk/edison/core2-32/i2c-tools-dev_3.1.1-r0_....perl-dev:unsatisfiedrecommendationforperl-module-pod-checker-devi2c-tools-dev:unsatisfiedrecommendationfori2c-tools-misc-devInstallingperl-dev (5.20.0-r1) on root. Downloadinghttp://iotdk.intel.com/repos/3.5/iotdk/edison/core2-32/perl-dev_5.20.0-r1_core.Configuringperl-dev.Configuringi2c-tools-dev.root@edison:~#
For those that already added the repo and want to check if it is already installed you can type opkg list-installed | grep i2c and should see something like this:
