Create a simple hello-world application

1. Overview

This stage explains how to create, build and execute a simple C code application using the freshly installed SDK.

2. Code

• Create a directory that will host your source codes

 mkdir $HOME/STM32MPU_workspace/STM32MP1-Ecosystem-v4.1.0/Developer-Package/stm32mp1-openstlinux-22.11.23
 mkdir $HOME/STM32MPU_workspace/STM32MP1-Ecosystem-v4.1.0/Developer-Package/stm32mp1-openstlinux-22.11.23/sources

• Create a directory for your user space example

 mkdir $HOME/STM32MPU_workspace/STM32MP1-Ecosystem-v4.1.0/Developer-Package/stm32mp1-openstlinux-22.11.23/sources/gtk_hello_world_example
 cd $HOME/STM32MPU_workspace/STM32MP1-Ecosystem-v4.1.0/Developer-Package/stm32mp1-openstlinux-22.11.23/sources/gtk_hello_world_example

• Create the source code file for your user space example: gtk_hello_world.c

#include <gtk/gtk.h>

static void
print_hello (GtkWidget *widget,
             gpointer   data)
{
  g_print ("Hello World\n");
}

static void
activate (GtkApplication *app,
          gpointer        user_data)
{
  GtkWidget *window;
  GtkWidget *button;
  GtkWidget *button_box;

  window = gtk_application_window_new (app);
  gtk_window_set_title (GTK_WINDOW (window), "Window");
  gtk_window_set_default_size (GTK_WINDOW (window), 200, 200);

  button_box = gtk_button_box_new (GTK_ORIENTATION_HORIZONTAL);
  gtk_container_add (GTK_CONTAINER (window), button_box);

  button = gtk_button_new_with_label ("Hello World");
  g_signal_connect (button, "clicked", G_CALLBACK (print_hello), NULL);
  g_signal_connect_swapped (button, "clicked", G_CALLBACK (gtk_widget_destroy), window);
  gtk_container_add (GTK_CONTAINER (button_box), button);

  gtk_widget_show_all (window);
}

int
main (int    argc,
      char **argv)
{
  GtkApplication *app;
  int status;

  app = gtk_application_new ("org.gtk.example", G_APPLICATION_FLAGS_NONE);
  g_signal_connect (app, "activate", G_CALLBACK (activate), NULL);
  status = g_application_run (G_APPLICATION (app), argc, argv);
  g_object_unref (app);

  return status;
}

3. Build

• Create the makefile for your user space example: Makefile

Information

All the indentations in a makefile are tabulations

PROG = gtk_hello_world
SRCS = gtk_hello_world.c

CLEANFILES = $(PROG)

# Add / change option in CFLAGS and LDFLAGS
CFLAGS += -Wall $(shell pkg-config --cflags gtk+-3.0)
LDFLAGS += $(shell pkg-config --libs gtk+-3.0)

all: $(PROG)

$(PROG): $(SRCS)
	$(CC) -o $@ $^ $(CFLAGS) $(LDFLAGS)

clean:
	rm -f $(CLEANFILES) $(patsubst %.c,%.o, $(SRCS))

• Cross-compile the project

 make

4. Deploy and execute

• Push this binary onto the board (Ethernet connection needed)

 scp gtk_hello_world root@<board ip address>:/usr/local

• Execute your user space example by using the user "weston"

 cd /usr/local/
 su -l weston -c "/usr/local/gtk_hello_world"                                                                                                                                              

• A GTK window is displayed

GTK Hello world window

• Click the "Hello world" button to close the window. Hello world is displayed on the console:

Hello world