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FreeRTOS - An introduction

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and so I said well hello and welcome to this talk about the articles let's 1st take the legal part
so this is this delivered by Creative Commons uh share which means you can reuse it's partially or completely long as you keep this license impact some
of the 1 my arm my means the an arm of being being uh images so for a consulting for a few years and I'm currently working for a company called minds so after this commercial break let's see our agenda how know and with introduction will what is basically free articles uh no talk a little bit about real-time basics then I'll talk about 3 articles configurations for poker Bots its API and you a small the but what's the flavor sophia articles and and its licensing so 3 apples is that pretty likely to operating system it's designed to run on microcontrollers and love just operating system itself states 5 to 10 to whites in flash and lots of 300 bytes on the run it's now supports some members prediction if you're CPU cost of course at but so it doesn't go any address translations on all the other these if that's the I hope it tasks in absolute priorities which means a higher task always 3 and sold prior task it will preemption is optional so you can slowing it down but this small sizes and all the configuration is done by see here there's the it's basically as I will show that's it's bunch of defining some symbols the so why would I use this operating systems because now currently we have a pretty powerful microcontrollers like a chip I'm familiar with this up out some force has runs its 120 megawatts that's pretty much faster than my 1st PC so with that much power you can handle a lot and as long as you want to do multiple things with a single-chip computers you will want to schedule down to prioritize them you need to communicate between your costs the and need to synchronize them so it was natural I have a really powerful single-chip computers so why not using operating system on that the spoke about real-time systems I'm assuming you're at least have a basic concept of what their real time system there's basically what they're what costs you are handling they have deadlines I unique to need those airlines the timing is critical at the end it's meeting deadlines means scheduling your costs as smart ways the that's so each deadline can be met not to die uh so you need to manage your priorities the and 1 way of managing those priorities is deciding which task is more important than which task is less important and skittling it that way so that's you basically saying some of the costs it's OK things their deadline and some of us are critical so let's keep them always in the highest priority all if anything limit the economics you know that a the most optimal way of managing deadlines is being your scheduling your priorities deadline based if you know your activation times and your deadlines and although to achieve these you need your system to be predictable the so of the articles or no piece of 2 little piece of software can turn a system into real time you need to design your system for me in real time and what free Arcos nozzle is amazing thing you the facilities to make your system predictable so that you can design it's in a real-time ways if these tasks absolute priorities so that's you know if I a priority task can run it will run he can be sure of that and obviously gives 0 sum dining facilities so that you can the late fossil-fired them in a repeated do unpredictable wage and as an innovative operating system that gives messaging queues and semaphores I'm in Texas so that's costs down communicate and synchronized and small notes uh all this operating system has been ported to many pieces of hardware screening microcontrollers basically each port harbor specifiche file is a single see file and it exists in his own directory file have I mean the and I will I'll show you that so this is a summary
of features to free operating system create real-time operating systems it's John from preemptable alternative FIL tasks by to management is uh flexible so that's if you are into that you can change priorities of the tasks will surprise uh also this priority inheritance mechanism to prevent priority in reference there are messaging shows the binary or counting semaphores now 1 recursive similar force no new Texas there are also several functions which makes a convenience store on separate in certain conditions like the call ronstadt theory got beach and I do runs repetitively as long as the CPU is idle it also it has a mechanism for checking for temporal preventing stack overflows and also if you will need tracing you can add additional quarks for tracing so this is how we call Figure 4 basically there's a file called free after stopping that you keep defining symbols enable preemption or not you can enable or disable so so books if you need than but we have some numerical parameters like how long the tasks in can be than if I want to use tracing if I want to use mutexes and so on and so on so this is what's a minimal uh mean function looks like in the hardware are used so uh meaning being Atmel microcontrollers the seas clock in it and water units are complete microcontroller functions they have nothing to do with its 3 articles and they're all 3 of those really the functions here is the task Starsky deliver on the life around the state the there is nothing about the apples and once I start the scandalous it's all uh stuttering Empiricus context while this did the without any tasks is nothing the so using this prototype I can adds some tasks a opacity is basically a wave function which ideally has an infinite loop inside and then by register my cost by calling the cost me it function with a pointer to my function with a strange name a stack size so specs sizes are fixed that's how we can check for speckle flows item pass parameters I can cost a priority an integer than defining it I can keep a handle to might ask if I need to FIL the possible plane its priority in the future here it's now because most of the time you don't need that and then use that the state of so I said we have several books these are some example books available there are normally defined as weak symbol so if you need to use them it can create find them we can compile them a petition title as I said before rounds when the when the processor is idle at the cookies it's clocked each and all of field is about loosely rounds many where MolLoc fails aspect of global Ronson aware steak all false and you see I get a handle the task and the 1 the string to the uh same parameter for the past name so I can immediately know something about which tasks has been stature we have a similar cost maybe I've basically it creates a binary semaphore you give and take them something important about interrupts is that's a lot of the API functions have the years From by a soft varience like here I have examined you and the sum of would you provide a soft if I'm running from within and interrupt service routine I need to use the from ISI routines so that it doesn't misleads the context switching also messaging Q 7 there of where I and Switzerland receive and from where an important part of that API is duly basically there are 2 functions 1 is make simple delays you call it function and your task this new late a number of takes you past and there is a smart function called delay on till right it takes 2 parameters previous make time and something instruments and as I will show you now it's smart in a way that it's automatically increments is on previous make up time and it's increments the previous make time in a way that's the task always calls periodically the the so I hope this is reader will use it this this is what's the cost function looks like basically I should have called the frequency interleaving periods so I have to make up periods idea it's a lost with time and then I stopped and infinite loop where told delay untill see that I don't do any manual updating and then called my what they were tossed functionalities and here is a
demonstration of how it's keeps the past periodic the bottom mean is the purple line in visible slightly again for the beats better colors they're purple tasks shows that it's a basic the LED switching past so it's acting on the on the transitions and if you look at the top the green line it shows the high priority tasks which states the CPU and hold the CPU as long as the green line is high and as long as it's world the task is hey idle so what I want to full here you is whenever sh the green lines off the CPU is missing that hi prior to cost the switching at the purple function is the late it's arrives late because it's set has a lower priority but it will not be 1 of its Mr. some deadlines for the next deadline still keeps periodic so it's the wake up time operates in a way that's not the actual time it wakes up not spectrally ran it was suppose to wake up this when you get some didn't but school role in a long periods the amount of findings is constant so he have several
flavors top uh they can talk about that license all the apples then mean free coasts licensees so-called what if I GPL they have what if I GPL because all the costs all the application-specific called gets statically leads into the apples so according to GPL everything must be don't details so the modified in a way that's you can't stick statically Lynch your application poultry apples and still give application called tool when they were license picture so what if I did realities technically not GPL at all lots there spirit of the license is the same so if you will do any changes all the apples in additions unit really 1 the same license but if you're just adding your application specific or dense typically linking it's the application-specific called down get the proprietor whatever license like there is a full term cannot flavor but an additional 3 apples plus which add some measles like you need the support online processing and some convenience functions which is available as source but if you want to know he was a commercially account by a license from those supporting company also if you need to nietzsche proprietor changes to operating system itself you can buy a license to ironically named open articles so that you can keep your cool closed also there is a flavor safe bottles for the same company Mrs. if you are working that's things like probablity where you needs safety the base of the idea of support for safety uh safety licensing and save save the certification the so this is
mainly what I have to say about real real-time operating system I can Baker questions shares of the least powerful system I don't know I haven't checked but basically I think if we have a whole thing the wife of a strand and saying 10 20 for flesh time can run it's it's it's uh 0 CPU this CPU they can participate this small it's basically if a bunch of functions and a scandalous so if you have enough flash and enough rent feature called I'm pretty sure it will run thing else yes the 1st layer of view of the time and you have so it asking if you will if I need to contribute back i need to sign that just sort it out yes since there are no yes you need to sign off your patches because they have is a clear that they have dual licensing each models so yes if you're 1 needs to be equal that's in the main 9 you need to sign sign of your copyright so the whole so will heap support yes if you would hey it's as their so asking if it is heap support as far as I know if you enable the should support it also allocates a certain what's in the in the round bears it can be a new parts from the as far as I know I'm not completely sure of that but as far as I know it's pre allocates at these for you you using for the heat yes to you know you want of how does it compare to other pH of 3 operating systems I don't have much experience with others I know that there are some operating systems like equals an art them so they have more features and have more high-level API so what I know about 3 articles is this is 1 of the most minimal systems you can find as a concrete's comparison I constantly the given answer I'm not so that that much mainly with that yes if you lost all yes which served which this set status of kids they have I don't know all of which which sort the dates they supports but so it they're safe by Oracle's homepage the goal is which certificates which ISO standard stable form so but I did not work with say potholes myself so I can't tell them the book my head pH Hey anything else yes will view the so we are asking for a real world application example while in 1 of my projects I was working for the and interface control interface for legal cannons a single microcontroller she was responsible for scanning sound there's standing at keypads LEED AES and also writing some happy in that feedback so that there must be a possible to the control haptic and visual feedback if you want to especially keep complex and my looking patterns at the same time you need to keep extending your sound there's any that at the same time you need to listen to all keypad events and also listen to the network if I I really want to you I can write down In a shoot for loop weights which interconnected spaghetti but I found that we call meaningful for uh rights for each task is a separate mouth separate and synchronize them weights too long and makes it unnecessary so I hope that some sets finances yes the work of the scientific the nucleus you you and I can only and so you ask what's tools are short and the for debugging 3 apples gives some hope some facilities for tracing and I'm familiar with the if few commercial tools for of from actually that's if you use their or official development tools they have that tracing utility that you can lope events into the RAM and download them via sealed about why costs J. kind also there are some the monitor applications that's again using citywire or j take can hold your CPU and at that moment you can down statistics like running processes this state off message queues the state of each new takes and information about tasks like how much step they're using and if they're running low or blocked off in whatever conditions and in the book or on time you know all of these thank you for attending were listening to you have to be a few
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Arithmetisches Mittel
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Patch <Software>
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Metadaten

Formale Metadaten

Titel FreeRTOS - An introduction
Alternativer Titel Embedded - Freertos
Serientitel FOSDEM 2015
Autor Filiz, Atilla
Lizenz CC-Namensnennung 2.0 Belgien:
Sie dürfen das Werk bzw. den Inhalt zu jedem legalen Zweck nutzen, verändern und in unveränderter oder veränderter Form vervielfältigen, verbreiten und öffentlich zugänglich machen, sofern Sie den Namen des Autors/Rechteinhabers in der von ihm festgelegten Weise nennen.
DOI 10.5446/34374
Herausgeber FOSDEM VZW
Erscheinungsjahr 2016
Sprache Englisch
Produktionsjahr 2015

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