DevHeads IoT Integration Server•5mo ago

How can I initialize the I2C bus on the BeagleBone Black Rev C running Embedded Linux?

Hey guys, how can I initialize the I2C bus on the BeagleBone Black Rev C running Embedded Linux? I am getting the error Failed to open the bus: No such file or directory, but I have verified that the I2C module is loaded and checked the device tree overlay. Here are the steps I took to verify the I2C module: 1. Loaded the I2C module using modprobe i2c-dev. 2. Checked that the device tree overlay for I2C is applied correctly. The error occurs when attempting to open the I2C bus

#include <linux/i2c-dev.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>

int main() {
    int file;
    char *bus = "/dev/i2c-1";
    if ((file = open(bus, O_RDWR)) < 0) {
        perror("Failed to open the bus");
        return 1;
    }
    return 0;
}

#include <linux/i2c-dev.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>

int main() {
    int file;
    char *bus = "/dev/i2c-1";
    if ((file = open(bus, O_RDWR)) < 0) {
        perror("Failed to open the bus");
        return 1;
    }
    return 0;
}

8 Replies

Sterling•5mo ago

Well, @Boss lady I would suggest you check if the I2C device nodes exist under /dev. Normally, it's named as /dev/i2c-X .

Sterling•5mo ago

And the X stands for Bus No.

Ming•5mo ago

Some other things to check (Examples and responses from my BBB which has i2c working): The version of the BBB Image you are using

 
debian@BeagleBone:~$ cat /etc/issue  
Debian GNU/Linux 11 \n \l

BeagleBoard.org Debian Bullseye IoT Image 2023-09-02
Support: https://bbb.io/debian
default username:password is [debian:temppwd]

 
debian@BeagleBone:~$ cat /etc/issue  
Debian GNU/Linux 11 \n \l

BeagleBoard.org Debian Bullseye IoT Image 2023-09-02
Support: https://bbb.io/debian
default username:password is [debian:temppwd]

If the i2c modules are loaded (not always an issue if not)

debian@BeagleBone:~$ lsmod | grep i2c
debian@BeagleBone:~$

debian@BeagleBone:~$ lsmod | grep i2c
debian@BeagleBone:~$

(No modules on my system) Any messages in the bootlog:

debian@BeagleBone:~$ dmesg | grep i2c
[    8.803295] omap_i2c 4802a000.i2c: bus 1 rev0.11 at 100 kHz
[    9.367701] omap_i2c 4819c000.i2c: bus 2 rev0.11 at 100 kHz
[   10.567358] i2c /dev entries driver
[   10.744849] input: tps65217_pwr_but as /devices/platform/ocp/44c00000.interconnect/44c00000.interconnect:segment@200000/44e0b000.target-module/44e0b000.i2c/i2c-0/0-0024/tps65217-pwrbutton/input/input0
[   10.747918] omap_i2c 44e0b000.i2c: bus 0 rev0.11 at 400 kHz

debian@BeagleBone:~$ dmesg | grep i2c
[    8.803295] omap_i2c 4802a000.i2c: bus 1 rev0.11 at 100 kHz
[    9.367701] omap_i2c 4819c000.i2c: bus 2 rev0.11 at 100 kHz
[   10.567358] i2c /dev entries driver
[   10.744849] input: tps65217_pwr_but as /devices/platform/ocp/44c00000.interconnect/44c00000.interconnect:segment@200000/44e0b000.target-module/44e0b000.i2c/i2c-0/0-0024/tps65217-pwrbutton/input/input0
[   10.747918] omap_i2c 44e0b000.i2c: bus 0 rev0.11 at 400 kHz

I have the i2c devices

debian@BeagleBone:~$ ls /dev/i2c*
/dev/i2c-0  /dev/i2c-1  /dev/i2c-2

debian@BeagleBone:~$ ls /dev/i2c*
/dev/i2c-0  /dev/i2c-1  /dev/i2c-2

Boss lady•5mo ago

@Sterling I have checked and it does exist

Sterling•5mo ago

Alright then, @Boss lady you will have to load in the I2C modules. It's simple, just run the following code;

sudo modprobe i2c-dev

sudo modprobe i2c-dev

Afterwards, check if it's successful by running the following on your terminal;

lsmod | grep i2c

lsmod | grep i2c

Sterling•5mo ago

I hope this helps ☺️

Boss lady•5mo ago

Thanks @Sterling although, I have already loaded my I2C module using the mod probe command it's still not displaying any output

Ming•5mo ago

@Boss lady What version of the Kernel are you running? You can find out by executing

uname -r

uname -r

I'm running the stock BBB image with the 5.10 kernel and am using my i2c.

Gaming

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How can I initialize the I2C bus on the BeagleBone Black Rev C running Embedded Linux?