Set up a cross-compilation environment and use NetBeans to debug code running on a Raspberry Pi

2018-01-22

Introduction

This is part two of my quest to build BlueTooth Low Energy Peripherals for fun. The first part showed how to create a rudimentary Peripheral on a Mac. But really, it was to learn about how it’s done on a Mac, and I don’t see much interest in turning your Mac into a Peripheral. Let me know otherwise!

This installment is in preparation to making a Pi a Peripheral. Here I describe how I set up a cross-platform development hosted on a Mac, targeting a Pi. This includes debugging using NetBeans.

Here goes:

The Pi is great, but, alas, it’s slow. Also, I configured mine to be headless, so no IDE for me while working on it. I used this little “hello world” project to set up my environment for cross compiling, running and debugging arbitrary code from my Mac on to the Pi.

The development workflow is:

• Use the Mac to write code. You don’t have to use NetBeans as the IDE, although I suggest you do, since we will be using it to debug on the target.
• Use the makefile to transfer the binary to the pi.
• Use NetBeans to debug the code running on the Pi (remotely)

Cross compiling

It took me a long time to find a cross compiler. Most of the Googles came back with set up from Linux, and required a VM to connect to. This, of course, is an overkill, and I opted for the solution presented here. Thank you Jared Wolff!

I used Jared’s DMG that he created, and since I am running my Mac case-insensitive, I could not copy the toochain locally, and quickly got used to referencing the cross-compiler toolchain off a mounted volume.

Using the command line, it looks like this:

/Volumes/xtools/armv8-rpi3-linux-gnueabihf/bin/armv8-rpi3-linux-gnueabihf-g++ welcome.cc

To test that it works, scp it to your Pi and run it there.

Setting up NetBeans

NetBeans is the only IDE that I could get to configure for cross-platform development. XCode is a horror to work with when it comes to general, non-iOS or Mac development. CLion is awesome, but does not lend itself to such configurations and is based on CMAKE, which is an overkill for my needs. So NetBeans it is:

Create your project, or use the one in github. Select preferences (Command+,), select the “C/C++” tab at the top of the pane. There, click on the “Build tools” tab and hit click on “Add” at the bottom. Fill in the pane like so:

Beware The Gotcha

As you can see, NetBeans asks for the “Base Directory”. I thought that supplying the tool names would suffice, based on the base dir. For me at least, this did not work and Make complained about finding the tools. To solve it, I put the full path of the tools in the dialog and added them again in the project’s properties page. If you encounter the same problem, right click the project’s root and select “properties”. There, select “Build” and then “C Compiler” etc to add in the full paths:

Running on a Pi

Once you have some code worthy of being run on the Pi, you transfer the executable to it and run it remotely:

echo "Copying file"
scp "dist/Debug/GNU-Pi-MacOSX/welcome_1" pi@pi:~
echo "Running file"
ssh pi@pi -C "./welcome_1"

Remote debugging using NetBeans

Step-debugging the code in NetBeans is a treat.

Running the debugger on the Pi

Run the remote debugger:

gdbserver :1234 welcome_1

Here you’re telling gdbserer to run the welcome app on port 1234.

In NetBeans

From the menu, select “Debug”/”Attach debugger” and fill in the form:

• For debugger, select “remote debugger”
• For target, type “remote pi :1234” ‘pi’ is the pi’s host name (I put mine in /etc/hosts) ‘:1234’ is the port with which NetBeans will communicate on your Pi. This has to be the same port number that you selected in the gdbserver command above.

Hit OK, and a few seconds later, you will see NetBeans’s debugger interface. Step through the example to see it in action.

Beware The Gotcha

Unless specified otherwise, gdbdebugger will exit after a single run. That means you’ll have to re-issue the gdbserver command for a subsequent session.

Access the example

Please feel free to use, fork and improve this snippet, posted on github.

I hope you find the example useful!

Happy hacking!