How to Open I2C Bus

[Patrick]

Hi!

I’m a beginner working with the BerryIMU & Raspberry Pi for a university project. I am currently following the “Guide to interfacing a Gyro & Accelerometer with a Raspberry Pi” tutorial.

So far, I have successfully detected the berryIMU using ‘i2cdetect y -1’. My question is for the “Open I2C Bus” part.. how do i necessarily do that?

Do i have to install something first? and how do i open the I2C Bus?

Thanks 🙂

[Mark Williams]

Hi Patrick, did you follow the instructions on the page below?
https://ozzmaker.com/i2c/

Mark --OzzMaker.com --

[Patrick]

Yes, i did. I was able to get the addresses 🙂

My concern now is the next step which says:

— First, you need to open the I2C bus device file, as follows;

char filename[20];
sprintf(filename, “/dev/i2c-%d”, 1);
file = open(filename, O_RDWR);
if (file<0) {
printf(“Unable to open I2C bus!”);
exit(1);
}

How do I exactly do this? shall i type it on lxterminal? or make file. and the codes are “C”.. so is there a need to install cmake? Please help me understand, thank you.

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[Mark Williams]

The page explains the code that is linked at the top of the page. See the attached image

A summary of the steps to get working code;

Download the code;

git clone http://github.com/ozzmaker/BerryIMU.git

Enter the directory for this tutorial;

cd BerryIMU/gyro_accelerometer_tutorial01

Compile;

gcc -o gyro_accelerometer_tutorial01 -l rt gyro_accelerometer_tutorial01.c -lm

Run;

sudo ./gyro_accelerometer_tutorial01

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Mark --OzzMaker.com --

[Patrick]

Please bear with me.

When i type “cd BerryIMU/gyro_accelerometer_tutorial01” it gives me an error that says

“bash: cd: BerryIMU/gyro_accelerometer_tutorial01: No such file or directory”

what could be the cause of this problem? Note: all of the codes are located in home/pi

Although I’ve noticed that the tutorial codes are in “.c” format.. is the error connected to this?

Thanks.

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[Mark Williams]

do
cd BerryIMU
Then list the contents
ls -l

look for a directory similar to gyro_accelerometer_tutorial01. and then CD into the directory.

I think it is gyro_accelerometer_tutorial01_angles

Then compile

Mark --OzzMaker.com --

[Patrick]

Thanks, I have succesfully interfaced the gyro with accelero.. complete with readings 🙂

I have now moved to the Inclinometer tutorial and have experienced an error again.

I have successfully installed SDL by typing –> [pi@raspberrypi ~ $ sudo apt-get install libsdl1.2-dev libsdl-image1.2-dev libsdl-gfx1.2-dev libi2c-dev]

Then, I tried to complile by typing –> [pi@raspberrypi ~ $ gcc -o test test.c sdl-config –cflags sdl-config –libs] Its giving me multiple errors. Please see image attached.

Am i right to assume that this is because i should type gyro_acclerometer_tutorial02.c instead of test.c?
Because when i checked the codes, i didn’t find any “test.c” file in any of the folders. What should I do?

Thanks!

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[Mark Williams]

When you are within the correct directory, compile with;
gcc -o gyro_accelerometer_tutorial02 -lm gyro_accelerometer_tutorial02.csdl-config --cflagssdl-config --libs-lSDL_image -lSDL_gfx

Mark --OzzMaker.com --

[Mark Williams]

Actually, go to the correct directory and view the README file. It will show the command to compile

Mark --OzzMaker.com --

[Patrick]

Hi!

I’ve already entered the correct directory, and when i tried to compile (referencing from the README file), I’m getting multiple errors regarding the file gyro_acclerometer_tutorial02_inclinometer.c. Please see image attached.

Thanks.

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[Mark Williams]

Those are not errors.. they are warnings. You can disregard them. The program should compile successfully

Mark --OzzMaker.com --

[Patrick]

Hi!

I’m trying the new codes for “compass with tilt compensation” and was able to compile.. but after that no output was being shown?

What do i type next to run it? thanks.
Please see image attached.

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[Mark Williams]

Did you run the program with?;
sudo ./compass_tutorial02

Mark --OzzMaker.com --

[Patrick]

Yes, i did and it worked. Sorry for the stupid mistake 🙂

Altho i have another question regarding the Plotting of Uncalibrated Output using Mathematica.

In the guide it said “You will want to pipe the output to a file, which we will use for Mathematica.”
From what I understand, i should run sudo ./compass_tutorial01(uncalibrated compass) – copy the outputand save it as “rawdatauncalibrated.txt”

I have done that and saved the txt file in home/pi folder. But when i type: pi@raspberrypi ~ $ sudo compass_tutorial01 > rawdatauncalibrated.txt it is telling command not found. (see image)

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[Mark Williams]

The screenshot shows ‘command not found’
CD into the first tutorial directoy again;
CD BerryIMU/compass_tutorial01_basics
Then run the code
sudo ./compass_tutorial01 > rawdatauncalibrated.txt
BTW: You need to place ‘./’ in front of the executable. The guide was missing this.
This tells Linux to look for the executable in the current directory.

Mark --OzzMaker.com --

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