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FreeRTOS C++ Wrappers

Michael Becker

July 22, 2016 02:09

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Hi All,

For anyone who may be interested, I've created an object oriented interface on top of FreeRTOS using C++ classes that encapsulate most of the fundamental
APIs. They allow you to craft a project using C++ code and conventions while handling the interface logic between the C and C++ code for you.

This C++ API currently provides or encapsulates:

• Critical sections
• Mutexes
• Queues
• Reader / Writer locks (new feature)
• Semaphores
• Tasklets (Pended Functions)
• Threads (Tasks)
• Tick Hooks
• Ticks
• Timers

The project page (WIP):
https://michaelbecker.github.io/freertos-addons/

Version 1.0.0 of the code for download:
https://github.com/michaelbecker/freertos-addons/releases/tag/v1.0.0

And the complete repository where you can browse the code and project online:
https://github.com/michaelbecker/freertos-addons

This is actually part of a larger project of mine, where I'd like to continue to add functionality to FreeRTOS and make it publicly available through
github. With regards to the C++ wrappers, there are 18 demo / unit test programs specifically exercizing it. I also updated / modified the work
William Davy did in his Posix port to get all of the demos running on multicore Linux workstations for testing with the newer FreeRTOS versions. This revised Posix port I renamed to Linux port, since I ended up using a few Linux specific APIs in it.

Everything was testing successfully using FreeRTOS versions 8.2.3 and 9.0.0.

Best regards,
-Mike Becker

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3 comments

• 0
  
  Michael Becker July 31, 2016 11:50

  Hi All,

  I found a particularly bad bug in the first version of this. I describe it here:

  https://www.linkedin.com/pulse/apples-kumquats-perils-multi-threaded-polymorphism-michael-becker
  
  If you are evaluating this, you should use v1.0.2 or later.

  Best regards,

  -Mike Becker

• 0
  
  Javier June 15, 2017 03:17

  Very interesting and amazing job. I'm taking a look into it, but as embedded system programmer my first concern is about size in RAM and Flash for ARM Cortex cores. Latest FreeRTOS releases, I guess starting from 9.0, includes static object creation (no malloc). So far I haven't seen such a feature in your wrappers. Is there a chance that this feature is already included in your code (1.3.2)? 

  Greetings!

• 0
  
  Michael Becker June 17, 2017 13:38

  As of yet I've not incorporated FreeRTOS static object creation in the wrappers. It's on my list of things to do, but hasn't made it to the top yet for a few reasons. First, I'm expecting folks using C++ to be working with systems that have a little bit more memory. The C++ wrappers, and perhaps C++ period, may not be appropriate for an 8-bit PIC with 2k of RAM. That being said, if you are already using C++ many of the wrapper classes shouldn't add much overhead at all. You can also pick and choose which classes you include. For example, if you don't want RW locks, don't include that file. I've tried to keep the inter-class dependencies to a minimum exactly for that reason.

  Regarding malloc, over the years I've learned that malloc in and of itself isn't necessarily a bad thing on an embedded system. The real problems occur when you are malloc'ing and freeing things over and over again, causing memory fragmentation. A very successful pattern is to malloc once at the beginning of time then never free. This was the model I typically saw used on FreeRTOS projects prior to 9.0.0. I've used older versions of FreeRTOS just fine on an ARM7TDMI with 32k of RAM where it mallocs all of its task and queue storage. And I've used versions of C++ on that same processor without a problem too. You just have to watch your usage of STL there.