GPIO - Linux drivers

See the license of the code (copyright), please do not use the code for educational purposes.

Study on operating systems, working with GPIO.

This project contains the GPIO command where a seven segment display (in combination with a 74HC595 shift register) is controlled with a Raspberry Pi. Two different libraries are used, each of which implements GPIO. The first library is WiringPi, and was required to be user. The second library is BCM2835. I chose this one to use in a more generic way for the Raspberry Pi. The program can be compiled using CMake, an instruction is given below. Now follows an overview of the various program functionalities that are supported, and to which the seven segment display shows numbers.

• The --display or -d option. This will display a hexadecimal number between 0x0 and 0xF. You can use it as ./GPIO_HEX_DRIVER --display 0xA or ./GPIO_HEX_DRIVER -d 0xA.
• The --countup or -u option. This option counts from the number as argument to 0xF. You can use it as ./GPIO_HEX_DRIVER --countup 0xA or ./GPIO_HEX_DRIVER -u 0xA.
• The --countdown or -l option. This option counts from the number as argument to 0x0. You can use it as ./GPIO_HEX_DRIVER --countdown 0xA or ./GPIO_HEX_DRIVER -l 0xA.
• The --wait or -w option. This option is used in combination with the --countup and --countdown options, to specify a custom wait time while counting. You can use it as ./GPIO_HEX_DRIVER --countdown 0xA --wait 0xFF or ./GPIO_HEX_DRIVER -l 0xA -w 0xFF.
• The --help or -h option. This shows the application help, and explains all the options possible to control the seven segment display with hexadecimal numbers.

Build and execute

To compile this program I use CMake. To be able to use this on a Raspberry Pi you have to go through a number of steps. These steps are shown below:

1. Create a new folder in the project. This folder is used for various configuration files, and ultimately the program's executable. For example, create this folder like this and go into that specific folder (name doesn't matter):

   ../GPIO_LINUX:~$ mkdir cmake-build
   ../GPIO_LINUX:~$ cd cmake-build

2. Now all the different CMake files should be generated. This is necessary too eventually.

   ../GPIO_LINUX/cmake-build:~$ cmake -DUSE_WIRINGPI:BOOL=ON ..

   In the above case, the GPIO library used is WiringPi. To change this to the BCM2835 library, you have to turn of that variable with CMake again. It is possible as follows:

   ../GPIO_LINUX/cmake-build:~$ cmake -DUSE_WIRINGPI:BOOL=OFF ..

Note - use of the address sanitizer

If this program (when you want to run it) shows an error message, you have to execute the following command:

../GPIO_LINUX/cmake-build:~$ sudo rm /etc/ld.so.preload