Programming for an embedded app

Hello psh59

Welcome to the element14 Community, I will move this over to the Raspberry Pi 2 area as it is a better fit.

Thank you,

Jamie

The first is easy:

How To Autorun A Python Script On Raspberry Pi Boot

If it's not a Python script just substitute your compiled application for myscript.py.

As for the second, you will probably have to install a C compiler such as gcc (sudo apt-get install gcc-4.9 g++-4.9) and compile your code locally on there from the SD card.

I might even give this a try if I had MS Visual C: Tutorial: Developing a Raspberry PI app with Visual Studio

This is a good resource https://www.raspberrypi.org/resources/learn/

As is this site.

Good luck and let us know how it goes!

As to the first question, Bob Alexander answered this one and I agree. The second one depends where the MS Visual C environment is running. If on a PC, then you cannot because it relies on DLL's that are not compiled to run on ARM code for Raspberry Pi. If on the other hand, it is on Windows 10 2015 Visual C++ built for cross compiling for Raspberry Pi and the Pi runs Windows 10 (whew), the answer is yes. I agree that GCC (free as in beer) is a great alternative as stated above.

C

You wont want to use a Raspberry Pi for this, its not a real time device.  I "heard" you can get a real time OS but never used it.  The overhead of the OS is going to cause issues with devices that need exact timed pulses.

Feel free to post your code, I bet we can get it running faster.  if the arduino you are using is 8mhz perhaps a 16mhz version would work?  I am not so sure an ISR would be the way to go if this is the ONLY thing it is doing, it would be better to remove the ISR overhead IMO.  If you are using DigitalWrite etc you can get a major increase by simply using the pins IO ports instead.

Finally, if that doesn't work you need a faster MCU, such as a chipkitP with a Pic 32 should do the trick.  Here is a quick vid I made of a speed comparison between the chipkit PI and the nano.  the same code you write for the nano should work directly on the ChipKit.  On top of that you can do the optimizations I mentioned above and have more than 10 fold increase in speed.

ChipKit Pi Vs Arduinio Nano328 16mhz

http://www.element14.com/community/videos/16140/l/chipkit-pi-vs-arduinio-nano328-16mhz

You can also pick up a ChipKit UNO which is the same thing just a different layout.  Both are pretty cheap, I think the chipkit pi is cheaper.

If you find this information helpful or correct, please may "helpful" and/or mark as "correct answer".

Thanks!

Is it possible to booth the system and auto load an executable w/o having to login? I want it to run like an embedded system.

As the Linux or Unix root (super user), edit /etc/rc.local (E.g. `su gedit /etc/rc.local`).  Just before the `exet` statement at the end of the file, this is where you will insert a command to launch whatever it is that you want launched soon after boot time.  Note that rc.local is launched just after all of the other /etc/rcN.d scripts are launched.  For more details about "rc", investigate how Linux boots and how the "init" process (pid 1) works.

You probably do not want your stuff running as the root.  So, in /etc/rc.local, your command should be something like this:

     su -c 'COMMAND' MYUSERID

where

     COMMAND = is the absolute path name to your shell script

     MYUSERID = the user name under which you want COMMAND to run

When I do this, my shell script is always self contained i.e. I do not rely on any I/O redirection of environment variables setup for me.  Also, make sure that you check *every* exit code from any embedded executables or called scripts.

Log to a directory that MYUSERID has write-access to and that will survive a reboot (E.g. do not log to /tmp).  Always include "evidence" with each log entry such process ID, date, time, and context (what was the goal?).  I would write to file names that included the date so that these log files could be aged (yes, you need to write a log-ager).

I want to write the code in my MS Visual C environment. How do I compile it for running on the Raspberry. Do I copy the code on to the SD card and compile and run on the Raspberry?

My understanding that Windows is not yet ready for general-purpose computing on the RPi, just "IoT".  I would stick to Linux and C/C++ programming for Raspbian or one of the Ubuntu flavors.  The Gnu C/C++ compiler works very well for this purpose.  Also, there are other language options such as Java and Python which can handle GPIO.

Good luck and experiment with tools.  Report back!

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

Why not use a PLL?

What is a PLL and where do I find info on that?

https://en.wikipedia.org/wiki/Phase-locked_loop

C

Frequency-locked loops are a little slower but a little less tricky than phase-locked loops, but seem to get lumped in with PLLs and called "PLL' just the same.

If you are really, really old, you remember TVs that rolled when they warmed up.  The PLL eliminated that.