Programming for an embedded app

Is there one or two locations that can show me how to write a program from scratch.

From scratch, in a nutshell .....

If you used Visual Studio C/C++ already, then you do not need a lesson in the C/C++ languages themselves.  For C/C++ programming, you'll need to get used to employing two basic tools:

1. a GUI source code editor
2. the gcc Compiler

For #1, I prefer the `gedit` tool; for #2, I use the `gcc` tool.  Get them like this:

     sudo apt-get install gedit gcc

Another good tool for C/C++ development is `make`.  If `which make` doesn't show you that you already have it, then do this:

     sudo apt-get install make

The `make` utility, while quirky, allows you to automate compiling and perform maintenance tasks related to source code, libraries, and executables.  Actually, a "Makefile" can specify almost anything that you'd like.

A simplistic example:

• Establish a source repository.  E.g. I have one being a folder called "src" under my home directory.
• Under $HOME/src, create a folder called "hello".
• Open a terminal window and execute:

     cd $HOME/src/hello

     gedit hello.c

• Enter the following lines, save, and then exit from gedit:

     #include <stdio.h>

     int main ( int argc, char **argv ) {

          printf ( "Howdy, y\'all\n" );

          return 0;

     }

• Still in $HOME/src/hello, execute:

     gcc -o hello hello.c

• Execute the compiled program:

     hello

Some C/C++/gdb/make tutorials:

http://www3.ntu.edu.sg/home/ehchua/programming/cpp/gcc_make.html

http://pages.cs.wisc.edu/~beechung/ref/gcc-intro.html

http://cseweb.ucsd.edu/classes/fa09/cse141/tutorial_gcc_gdb.html

How do I get a display to work with gedit? I get an error "could not open X display".  I don't know what the possible values for X in "gedit --display=X" are.

What OS did you install?  Most folks use Raspbian (Raspberry Pi flavor of Debian) or a flavor of Ubuntu.  I mentioned that above.

See https://www.raspberrypi.org/downloads/

Raspian

Wrote this program as suggested above.

#include <stdio.h>

     int main ( int argc, char **argv ) {

          printf ( "Howdy, y\'all\n" );

          return 0;

     }

• Still in $HOME/src/hello, execute:

     gcc -o hello hello.c

• Execute the compiled program:

     hello

>> I just wanted to see that I could make it work. I don't recall having so many problems when I was using QNX many years ago but it won't execute. I get no errors and see hello in the directory as an executable (ls -l) but I get an error "hello: command not found". I changed the output file name to "test" and run it - I get no error but get no output. I know I am doing something stupid but I can't figure it out. I would have though there were some libraries somewhere that I would have to link to.

./hello is correct way to execute if you are in the current directory for hello

C

./hello is correct way to execute if you are in the current directory for hello

C

Thanks VERY much.

Thanks, Clem.  Some times I forget that my /etc/profile contains a statement that puts the current directory in the path:

     export PATH=.:$HOME/bin:$PATH

So, Paul, what is located as an executable depends on the value of $PATH.  This is analogous to %PATH% in Windows.

Paul,

You might recall that in Windows, you can also permanently change the %PATH% value.  This can be done with REGEDIT or one of the Windows 3rd party utilities.  I forget the Windows registry variable name as I haven't done Windows programming in quite a while.

In /etc/profile, I also included the $HOME/bin element so that I can develop private or speculative executables for use while logged in without having to install them somewhere.

I was away for a while and unable to try anything but I am back on the project and having problems with wiringPi. I downloaded everything a week ago so I'm sure I have the latest stuff. I got the program to build and I can run. I forgot to execute with root privileges but after executing with the sudo command the program executes. I can't seem to set and control and of the IO pins. I used wiringPiSetup() and used the logical pin numbers (2 for GPIO02 - header pin 3, 4 for GPIO04 - header pin 7) for pinMode(), digitalWrite() and digitalRead(). I had no luck seeing a low or a high on the pins I tried. I used a voltmeter to check the pins. I also tried wiringPiSetupPhys() and used the actual header pin numbers (3 for GPIO02, 7 for GPIO04).

I then tried to set all GPIO as outputs and set them low using a loop from i=2 to i<27. This seemed to set previous pins that were high to low but I'm not sure it was because I set them to zero because the program actually hung the system and I had to actually disconnect power to regain control. I suspect that the pin number being passed to the pinMode() and digitalWrite() is writing to somewhere that I don't expect it to.

I'm using Raspberry Pi 2 Model V1.1. Looking at the wiringPi.c code it looks like this model is supported. I am assuming that I am doing something wrong but I can't seem to figure it out. Anyone have any hints they can provide?

gpio readall command was an eye opener. Nice tool! My documentation that I was using for the pin assignments had the BCM numbering in bold and the wPi numbering greyed out even though the title on the diagram was Raspberry Pi2 GPIO Header. I guess I should have tried that numbering scheme since I wasn't getting anywhere with the others. My IO pins are now under control. Minor logic tweak in code to sort out and then performance testing. Thanks for help. Sorry for the trouble. Cheers.

If you like my answer, can you mark it helpful or correct?  I don't get very many of them.

Tell me how. Everyone's input has been great.

YOu may not be able to since it is assumed answered.  If you can, at the top not sure if you mark it as unanswered again.