Lab 3: Introduction to Kernel Modules

EE 474 Spring 2016

Contributors: Brad Marquez, Joseph Rothlin, Aigerim Shintemirova

The purpose of this lab is to further develop our embedded Linux skills by creating a Kernel module that replaces our user space code from previous labs which communicated with various periferal devices. In this lab we created a ButtonHero game (synonymous to Guitar Hero) using two periferal LCD screens as the disply, a shift register for injecting data into the LCDs, a 5-way directional button as the control, and a piezzo buzzer for sound effects. This project includes a kernel space driver for the button, a kernel space driver for the shift register/LCD setup, and a main user space program executing the game. The target device for this project is the BeagleBone Black with the ARM Cortex-A8 processor onboard.

1. With the Makefile use the "make all" command to cross compile the code
2. Again, with the Makefile use the "make transfer" command to transfer all the necessary file to the BeagleBone
3. SSH protocol is used to connect to the Beaglebone, use the command ssh root@192.168.7.2 to move to the BeagleBone
4. Use "insmod filename" to insert both of the .ko files into the Linux OS (You can use lsmod to make sure the modules were properly insert)
5. Use "dmesg tail" to display the messages from the inserted modules
6. Each module should have printed a line instructing how to create their device files. Use the quoted command to create the device file (one for each module) which will look something like "mknod /dev/string c # 0".
7. Congratulation! Now the software should be ready to go! Just run the ButtonHero executable to play!

This file acts as the single driver for both LCDs. Using the system open/close functions the user can intialize and uninitialize the LCD screens and GPIO pins. Using the system write call the user can provide up to 48 characters toimmediatly be printed to the two screens. Using the seperate enable pins for the LCDs this module can load the data to write to the shift register and then choose which screen to write to by selecting which enable pin to toggle.

This file acts as the driver for the 5-way button. Using the system open/close functions the user can initialize and uninitialize the GPIO pins associated with the button. Using the system read call the user can receive 20 bytes (5 integers) of data which contains the status of each direction on the button.

This file was written in user space C and uses both modules above to communicate with periferal devices while executing the game. This level of abstraction made communicating with periferals fairly simple from the perspective of ButtonHero.c. This program creates the visual effect of scrolling arrows across a screen during which the user is meant to press the corresponding button direction assosiated with that arrow. High scores are recorded and displayed at the end of each round, and a buzzer along with LEDs were added (and controlled by buttonHero.c) in order to increase the aesthetics of the game.

• Create unique symbols rather then generic keyboard arrows
• Create two player option
• Recreate ButtonHero.c using C++