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Loading-A-Driver-Module.md

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Introduction

Loading modules is easy, if you have the module file accessible via nfs or already loaded on the SD Card.

During the debugging phase, which is where I am most of the time, I load the modules using the command line, like this: sudo insmod some/path/to/module, but you can also do it via the startup scripts in Linux.

For now, we'll just use the manual method here. Note that you'll need shell access, either using ssh over wifi or soon we'll have RNDIS which will give us IP networking over USB.

  1. Somehow, get the kernel module, the file with .ko suffix available on the EV3 filesystem. This might mean removing the SD card and copying it manually, of if you've read the page on setting up an nfs fileshare you can access it over the network.

  2. Create the modules directory on the EV3: sudo mkdir /lib/modules

  3. Copy the module from the source to the EV3: sudo cp source/path/todriver.ko /lib/modules/driver.ko

  4. Load the driver manually: sudo insmod /lib/modules/driver.ko

  5. Unload the driver manually: sudo rmmod /lib/modules/driver.ko

Of course driver.ko should be replaced with the actual driver name!

Where to Find Driver Modules

The ev3dev repository has a directory named modules that has all the currently available driver modules.

Automatically Load EV3DEV Driver at Boot Time

Boot the EV3 from the SD card and open an SSH connection with the EV3 via USB or WiFi using root credentials. At first you have to update the dependency files with

depmod

which updates the files in the folder /lib/modules/3.3.0/. Then the EV3DEV kernel modules can be configured to start at boot time with

echo ev3dev >> /etc/modules
echo ev3dev_ui >> /etc/modules
echo ev3dev_pwm >> /etc/modules

Restart the EV3

shutdown -r now

and verify with

lsmod

that the configured kernel modules

  • ev3dev,
  • ev3dev_ui for LEDs, and
  • ev3dev_pwm for motors are loaded.

Then the folder /sys/devices/platform/ev3dev/ should be available. See Examples Using EV3DEV.