libioctrl

Warning

In this chapter we are going to combine our previous source code into a centeralised directory.

1. Setting up the libioctrl source code:

  1. Create a new directory in home called libioctrl:

    Terminal

    $ mkdir -p ~/libioctrl/{src, include}

  2. We need to copy the adc.{c/h} , gpio.{c/h} and pwm.{c/h} from the respective directories into two new child directories inside of libioctrl, src and include:

    Terminal: Example

    $ cp adc/adc.c ~/libioctrl/src && cp adc/adc.h ~/libioctrl/include

    Repeat for each of the other libraries we had made earlier.

  3. You should have the following structure:

    Output

    $ ls -l ~/libioctrl/*
libioctrl/include:
total 12
-rw-r--r-- 1 debian debian  685 Apr 14 19:25 adc.h
-rw-r--r-- 1 debian debian 2557 Apr 14 20:35 gpio.h
-rw-r--r-- 1 debian debian 1636 Apr 14 20:35 pwm.h

libioctrl/src:
total 12
-rw-r--r-- 1 debian debian 1288 Apr 14 19:24 adc.c
-rw-r--r-- 1 debian debian 3559 Apr 14 19:46 gpio.c
-rw-r--r-- 1 debian debian 2490 Apr 14 19:24 pwm.c

  4. Now make a new libioctrl.h inside the include/ and fill the following:

    Code: include/libioctrl.h

    #ifndef LIBIOCTRL_H
#define LIBIOCTRL_H

#include "gpio.h"
#include "pwm.h"
#include "adc.h"

#endif // LIBIOCTRL_H

  5. Replace the #include "adc.h", #include "gpio.h" and #include "pwm.h" inside the respective .c files:

    Code: src/adc.c

    # include "../include/adc.h"

    Repeat for the other .c files

  6. Next we need to update some variable names to deal with the issue of multiple declarations when compiling. Inside include/pwm.h change the following, we are only appending PWM to PinMap:

    Old:

    Suppressed code [15 lines]...

     
    // Structure to hold PWM mapping information
typedef struct {
    char physical_pin[10];  // Physical pin on the BeagleBone Black (e.g., "P9_16")
    char pwm_chip_channel[10]; // PWM chip and channel (e.g., "4:1")
} PinMap;
...
// Define the pin_map array with physical pins and their corresponding PWM chip:channel
PinMap phy_pin_map[] = {
    {"P9_16", "4:1"},  // eHRPWM1B
    {"P9_14", "4:0"},  // eHRPWM1A
    {"P9_21", "1:1"},  // eHRPWM0B
    {"P9_22", "1:0"},  // eHRPWM0A
    {"P8_13", "7:1"},  // eHRPWM2B
    {"P8_19", "7:0"},  // eHRPWM2A
    {"P9_28", "3:0"},  // eCAP1
    {"P9_42", "0:0"}  // eCAP0
};

    New:

    Suppressed code [15 lines]...

     
    // Structure to hold PWM mapping information
typedef struct {
    char physical_pin[10];  // Physical pin on the BeagleBone Black (e.g., "P9_16")
    char pwm_chip_channel[10]; // PWM chip and channel (e.g., "4:1")
} PWMPinMap;
...
// Define the pin_map array with physical pins and their corresponding PWM chip:channel
PWMPinMap phy_pin_map[] = {
    {"P9_16", "4:1"},  // eHRPWM1B
    {"P9_14", "4:0"},  // eHRPWM1A
    {"P9_21", "1:1"},  // eHRPWM0B
    {"P9_22", "1:0"},  // eHRPWM0A
    {"P8_13", "7:1"},  // eHRPWM2B
    {"P8_19", "7:0"},  // eHRPWM2A
    {"P9_28", "3:0"},  // eCAP1
    {"P9_42", "0:0"}  // eCAP0
};

    Update the src/pwm.c to reference the PWMPinMap inside sizeof(...):

    Code

    for (int i = 0; i < sizeof(phy_pin_map) / sizeof(PWMPinMap); i++) {
    if (strcmp(phy_pin_map[i].physical_pin, pin_name) == 0) {
        // Parse the pwmchip and pwm channel
        sscanf(phy_pin_map[i].pwm_chip_channel, "%[^:]:%s", pwm_channel, pwm_chip);
    }
}

  7. Next we need to update some variable names to deal with the issue of multiple declarations when compiling. Inside include/gpio.h change the following, we are only appending GPIO to PinMap and gpio_ to pin_map:

    Old

    Suppressed code [10 lines]...

     
    // Define a simple mapping array for P8 and P9 pin names to GPIO numbers
typedef struct {
    char pin_name[6];
    unsigned int gpio_number;
} PinMap;
...
// Static array to map pin names to GPIO numbers
PinMap gpio_pin_map[] = {
    {"P8_31", 10}, {"P8_32", 11}, {"P9_31", 110}, {"P9_29", 111},
    ...
}

    New

    Suppressed code [15 lines]...

     
    // Define a simple mapping array for P8 and P9 pin names to GPIO numbers
typedef struct {
    char pin_name[6];
    unsigned int gpio_number;
} GPIOPinMap;
...
// Static array to map pin names to GPIO numbers
GPIOPinMap gpio_pin_map[] = {
    {"P8_31", 10}, {"P8_32", 11}, {"P9_31", 110}, {"P9_29", 111},
    ...
}

    Update the src/gpio.c to reference the gpio_pin_map and GPIOPinMap inside sizeof(...), remember to replace all the instances of pin_map in the below function to gpio_pin_map:

    Code

    // Function to find GPIO number from pin name
int find_gpio_number(const char *pin_name) {
    for (int i = 0; i < sizeof(gpio_pin_map) / sizeof(GPIOPinMap); i++) {
        if (strcmp(gpio_pin_map[i].pin_name, pin_name) == 0) {
            return gpio_pin_map[i].gpio_number;
        }
    }
    return -1;  // Return -1 if the pin is not found
}

2: Make with a Makefile

Warning

  • Before running make for libioctrl, we should remove all current libaries from before. For each original library, adclib, gpiolib, pwmlib or whether you made them run make uninstall and make clean in each one:

  1. Build a Makefile and fill with the following:

    Suppressed code [55 lines]...

     
    # Compiler and flags
CC = gcc
CFLAGS = -Wall -Werror -fPIC -I./include  # Include headers
AR = ar
ARFLAGS = rcs
PREFIX = /usr
INCLUDEDIR = $(PREFIX)/include
LIBDIR = $(PREFIX)/lib

# Directories
SRCDIR = ./src
OBJDIR = ./obj

# Library names
TARGET_STATIC = libioctrl.a
TARGET_SHARED = libioctrl.so

# Source files for each component
SRC = $(SRCDIR)/gpio.c $(SRCDIR)/pwm.c $(SRCDIR)/adc.c
OBJ = $(patsubst $(SRCDIR)/%.c, $(OBJDIR)/%.o, $(SRC))

# Default target: Build both libraries
all: $(TARGET_STATIC) $(TARGET_SHARED)

# Compile source files into object files
$(OBJDIR)/%.o: $(SRCDIR)/%.c
        @mkdir -p $(OBJDIR)
        $(CC) $(CFLAGS) -c $< -o $@

# Create the static library
$(TARGET_STATIC): $(OBJ)
        $(AR) $(ARFLAGS) $@ $(OBJ)

# Create the shared library
$(TARGET_SHARED): $(OBJ)
        $(CC) -shared -o $@ $(OBJ)

# Clean up build artifacts
clean:
        rm -rf $(OBJDIR) $(TARGET_STATIC) $(TARGET_SHARED)

# Install libraries and headers
install: $(TARGET_STATIC) $(TARGET_SHARED)
        sudo cp include/gpio.h include/pwm.h include/adc.h include/libioctrl.h $(INCLUDEDIR)/
        sudo cp $(TARGET_STATIC) $(TARGET_SHARED) $(LIBDIR)/
        sudo ldconfig

# Uninstall libraries and headers
uninstall:
        sudo rm -f $(INCLUDEDIR)/gpio.h $(INCLUDEDIR)/pwm.h $(INCLUDEDIR)/adc.h $(INCLUDEDIR)/libioctrl.h
        sudo rm -f $(LIBDIR)/$(TARGET_STATIC) $(LIBDIR)/$(TARGET_SHARED) $(OBJDIR)
        sudo ldconfig

# Phony targets
.PHONY: all clean install uninstall

  2. We need to remove all reference to libraries created before, navigate to adc, gpio and pwm directories and run:

    Terminal

    path/to/adc$ make uninstall
...

  3. Go back to the libioctrl and run make:

    Output

    path/to/libioctrl$ make install
gcc -Wall -Werror -fPIC -I./include   -c src/gpio.c -o obj/gpio.o
gcc -Wall -Werror -fPIC -I./include   -c src/pwm.c -o obj/pwm.o
gcc -Wall -Werror -fPIC -I./include   -c src/adc.c -o obj/adc.o
ar rcs libioctrl.a  ./obj/gpio.o  ./obj/pwm.o  ./obj/adc.o
gcc -shared -o libioctrl.so  ./obj/gpio.o  ./obj/pwm.o  ./obj/adc.o
sudo cp include/gpio.h include/pwm.h include/adc.h include/libioctrl.h /usr/include/
sudo cp libioctrl.a libioctrl.so /usr/lib/
sudo ldconfig
...

  4. Breaking down the output of make install:

    Object file compilation:

    • The gcc command is compiling each source file (src/gpio.c, src/pwm.c, and src/adc.c) into object files (obj/gpio.o, obj/pwm.o, and obj/adc.o), and it uses the appropriate flags (-Wall, -Werror, -fPIC, -I./include).

      Terminal

      gcc -Wall -Werror -fPIC -I./include   -c src/gpio.c -o obj/gpio.o
gcc -Wall -Werror -fPIC -I./include   -c src/pwm.c -o obj/pwm.o
gcc -Wall -Werror -fPIC -I./include   -c src/adc.c -o obj/adc.o

    Creating the static library:

    • The ar rcs command is creating the static library libioctrl.a by combining the compiled object files gpio.o, pwm.o, and adc.o.

      Terminal

      ar rcs libioctrl.a  ./obj/gpio.o  ./obj/pwm.o  ./obj/adc.o

    Creating the shared library:

    • The gcc -shared command is creating the shared library libioctrl.so by linking the same object files gpio.o, pwm.o, and adc.o

      Terminal

      gcc -shared -o libioctrl.so  ./obj/gpio.o  ./obj/pwm.o  ./obj/adc.o

    System wide availability:

    • This command copies the header files (gpio.h, pwm.h, adc.h, and libioctrl.h) to the system's /usr/include/ directory. This makes the header files available system-wide, allowing programs to include these headers when building applications that use the library.

      Terminal

      sudo cp include/gpio.h include/pwm.h include/adc.h include/libioctrl.h /usr/include/

    • This command copies the static (libioctrl.a) and shared (libioctrl.so) versions of the libioctrl library to /usr/lib/, which is a standard system library directory. This allows programs to link against the library when building.

      Terminal

      sudo cp libioctrl.a libioctrl.so /usr/lib/:

    • This command updates the system's dynamic linker cache. It ensures that the system is aware of the newly installed shared libraries (e.g., libioctrl.so) so that applications can find and use the shared library at runtime

      Output

      sudo ldconfig

Using our new library

  1. Update any of the following tests we ran before; adc2pwm.c, adc_continous_read, adc_read, blink and pwm_test:

    In this example I will update the adc_read.c headers and part of the Makefile:

    adc_read.c

    Code

    #include "libioctrl.h" # originally adc.h
#include <stdio.h>
#include <unistd.h>
...

    Makefile

    Code

    ...
# Library to link against
LIBS = -lioctrl # originally, ladc
...

    You should repeat for the others, and remember to make clean before running make for each of these programs to remove original exe.

Fork and Clone Libioctrl library

  1. Incase it doesn't work as intended, you can fork and download the libioctrl library from GitHub:

  2. Clone the forked repo: git clone git@github.com:YOURUSERNAME/bb.black_pin_library

  3. cd to the parent directory of where you cloned the repo using shell copy command, scp:

    Terminal

    scp -r /path/to/bb.black_pin_library debian@192.168.7.2:c_libraries

  4. You should then be able to install the library via the bash install.sh script within the repo:

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Page last updated: Thursday 26 June 2025 @ 14:13:31 | Commit: 812dc97