I have not done any programming for years. We were using FORTH at the time. This has been very interesting as to what my software buddies, and perhaps me again some day, have to consider.
So, I can only thank Jack for bringing real-time wisdom to the MPU design world. After all, concurrent issues will continue to rise, perhaps exponentially. :o)
I don't know why i can only write in capital. it's not the caps lock.
the high level lenguages do have varying degrees of overhead. however. there is no guarnatee that a program designed in high level will get more machine instructions than a code developed in assembler, except for very simple programs.
i will let jack answer that question in more accurate terms.
Modern Ada might be very good, but how does it get around the problem you've shown in the initial slides? Does Ada say: Sorry, dear, not on this platform, I have a headache?
What demands does Ada have on the underlying hardware? Looking at the first slides, I get suspicious if high-level languages claim to be able to do realtime things.
Modern Ada compilers are very good. The RAVENSCAR profile (a set of features) leads to very small code basis.
Jack, don't you think the industry needs to develop a benchmark tool, so that NON-RT solutions can be compared to standard (to be developed) RT ones so designers can strech their artistic/intuitive achievements? That would make the RTOS part of a standard metric.
RTOS developers publish code execution time guarantees based upon scheduling algorithm they employ? What characteristics are made available for those who intend to use the RTOS, from which to evaluate the worth of adopting it?
Most RTOSes are very fast; if the diff in speed between two RTOSes is a concern then I think one should be looking at a better CPU. The differentiators are the features - and you need to know which ones you need - pricing, royalty models and support. The vendors are pretty good at advertising their feature sets, and not so good at advertising costs and support. I've worked with a lot, and have found them generally very, very good. The more complex add-ons you buy - like TCP/IP - the higher the odds you'll find problems.
luizcosta: your capslock is on What demands does Ada have on the underlying hardware? Looking at the first slides, I get suspicious if high-level languages claim to be able to do realtime things.
RTOS developers publish code execution time guarantees based upon scheduling algorithm they employ? What characteristics are made available for those who intend to use the RTOS, from which to evaluate the worth of adopting it?
SPEAKING OF REALIABILITY ADA IS ONE OF THE FEW (IF NOT THE ONLY ONE) LANGUAGES THAT HAVE REAL-TIME INSTRUCTINS TO DEAL WITH CONCURRENCY. FOR THOSE WHO ARE NOT FAMILIAR WITH THE CREATION OF ADA IT STARTED BY THE DEPT OF DEFENSE THAT MADE THE FIRST EFFORT TO ORGANIZE THE TOO MANY OPTIONS IN THE MARKET. THERE IS A GROUP IN THE ADA COMMUNITY FOR EXAMPLE THT IS DEVELOPING CODE WITH THE LEGO MINDSTORM BORADS.
jack21: How far would you go before using an RTOS? If you, e.g. partition your system sufficiently far, you might be able to pull off some amazing things with very simple architecture for the single MCU. I am amazed at what Chuck Moore's most recent generation of chips does...
Tough question! An RTOS will bring added complexity. But if your system needs to manage multiple independent things, consider one. For instance, if it has to handle buttons, display, comm, and whatnot non-RTOS code quickly gets ugly.
How can one get an idea of speed as a performance objective vs the compiler employed?
You can demand it from the vendor, but few know. All one can do is run tests for critical sections of code. I think it's criminial they don't profile their stuff, but after years of nagging them have had no luck.
jack21: How far would you go before using an RTOS? If you, e.g. partition your system sufficiently far, you might be able to pull off some amazing things with very simple architecture for the single MCU. I am amazed at what Chuck Moore's most recent generation of chips does...
JACK, IN MY VIEW, THE BEST ASPECT OF YOUR PRESENTATION, IS THAT IT HAPPENED. I REFER TO THE FACT THT IT SHOW THAT COMPANIES ARE AWAKENING TO A NEW GENERATION OF EMBEDDED SYSTEMS FOR MORE EFFICIENT TECHNOLOGICAL DEVELOPMENT. AFTER ALL, IT'S ALL ABOUT DESIGN EFFICIENCY IN A FAST PACED AND MORE COMPLICATED WORLD.
one thing that has been bugging me: to RTOS or not to RTOS ... whether 'tis better for my peace of mind if I know the slings and arrows of my own doing or, by reusing prebuilt stuff, suffer
I think it's a bad idea to reinvent the wheel. Fun, you betcha. But it's tough to get an RTOS right. Most of the homemade ones I see don't have much in the way of queues, mailboxes and the like, so the reentrancy issues for the application become huge.
huh ... I might have inadvertently described the difference between what Jack called a "programmer" and an "engineer" ... i.e. narrow-minded code-monkey-ness vs. system-level cogitation
one thing that has been bugging me: to RTOS or not to RTOS ... whether 'tis better for my peace of mind if I know the slings and arrows of my own doing or, by reusing prebuilt stuff, suffer
and most of all: the software developer _must_ know what he/she is doing. Most of the failures I see can be attributed to the "not my problem" attitude
re linux and realtime... I know high-load servers getting sooo busy that monitoring software reports them as "down" because they won't respond to ping within 10 seconds, since they're too busy flushing stuff to disk.
Linux was never meant for embedded, but embedded grew so that the processors could handle it. It still requires a lot of power and memory.
I RECOMMEND THE NEW BOOK (2012) BY DOUG COMER FROM PURDUE. HIS NEW BOOK ON OS DESIGN WORKES FROM THE VERY SIMPLE OS ROUTINES TO THE MORE INTRICATE ONES. AND ALL THE CODE IN THE BOOK CAN RUN ON XINU. AS A MATTER OF FACT HE TEACHES HOW TO COMPLETE THE XINU BASIC KERNEL.
re linux and realtime... I know high-load servers getting sooo busy that monitoring software reports them as "down" because they won't respond to ping within 10 seconds, since they're too busy flushing stuff to disk.
Is there any book which have similar special tips on effective coding in embedded systems like what you had mentioned? I had remained for long hardware wngineer
Some in the David Simon book. But otherwise, alas, no.
Is there any book which have similar special tips on effective coding in embedded systems like what you had mentioned? I had remained for long hardware wngineer
Do you think Android is stable enough to meet the reliability demands of embedded systems and devices?
For some systems it's fine. For high-rel or high-security it's not. Linux is rated at security level EAL4+, the same as Windows; EAL4 means it's secure if no one tries to break in. I don't think Android has been rated yet.
YOU KNOW, JACK, I'VE BEEN TEACHING IN ENGINEERING TECHNOLOGY PROGRAMS FOR THE LAST 4.5 YEARS, AND I NEVER HEARD OF ANYONE TEACHING ABOUT "IMPEDANCE MATCH." ISN'T THAT CRAZY, WHAT IS HAPPENING IN EDUCATION?
I READ THAT LINUX AS A RTOS IS IFFY, IS THAT A CORRECT ASSESSMENT?
Linux is not real-time, but some people run it on top of an RTOS, like VxWorks. Linux handles files, comm, etc, and the other tasks do the really real time stuff.
slide 13: is there a "correct" way to wait for a resource to become available again? Or is the answer going to be "don't wait, have somebody tell you?"
slide 25: how do/can you avoid bouncing when your scope cables _are that long_?
Doesn't matter if they are properly set up. The issue with probes is rise time. You can make a very fast probe with 3' of RG-58U, a short 1K resistor on the end, very tight braid-to-board line. And, you must set your scope for 50 ohm impedance. This is a divide by 21 probe, but it is excellent.
Linux's success (and Android) in the mobile market is largely due to the great ARM ports, the so-called "free" nature of it, it works well, and it supports a zillion I/O devices.
It is interesting that we seem to re-experience everything. Mathematical approximations for the mainframe, then for midrange, then PCs and finally into the world of Embedded Systems.
Q.1 Any similarity to the use of semaphores and saving of program state while executing critical portions of code?
Q.2 Are the use of shceduling algorithms also incorporated for multi-tasking? how does this OS timing and application routine timing accounted for in evaluating worst case response?
YES, RIM BOUGHT UP QNX SOFTWARE SYSTEMS IN THE SUMMER OF 2010 SO THEY CAN KEEP THE CARS AND DON'T LOOSE THE EDGE WITH THE USE OF SMART DEVICES IN THE AUTO INDUSTRY, WHICH THEY ALREADY HAVE SIGNIFICAN PRESENCE.
The "Cool Tools" page on Jack's website - http://www.ganssle.com/tools.htm - is really, really impressive. A quick glance at that page and I already found a good replacement for HyperTerminal. HyperTerm is no longer supported by MSFT and does not work on Win 7.
Have you done any work, or recommend anything using parallel processing for real time measurements, or other things?
Multicore is the rage (in the press) but often has big problems unless the problem is inherently parallel. Async multicore (two or more CPUs with their own address space is a great solution.
From a learning perspective, can you recommend a means for a newbie to detect when some of these problems you mention have occurred? It isn't likely trace function in an in-circuit emulator will be in use or anything equipment that is expensive will be used in a learning environment.
Great advice. I don't do a lot of real time development but your impedance matching advice is overlooked in many technologies. I also discovered that fluid flow has flow into the male and out the female fittings so the electrical signals also need to follow this pattern.
not everyone is using the chat window. some are downloading the slide deck as directed above. it would be helpful to have the ppt slide pages to identify the page number though.
Question: Can you give some good references for learning more about creating "C" implementations of complex computation, such as sin, cos, hyp tan, exp, etc.? I've heard about CORDIC, but would love to target some good analysis, rather than read a bunch of "teaser" articles/books. Thanks! Interesting talk!
Interesting thing is that folks who nowadays work with microelectronics they had to go back to school (real engineering) to learn microwave engineering. In the past and still today in engineering/techn ical schools, students want to skip all that "nightmare"
Thanks. BTW: if anyone works where the audio stream is blocked and they have a smartphone they can get the audio via the smartphone while using their desktop for the slide deck and chat.
my military electronics education many years ago was great. we understood how the logic works, signal voltage, timimg and troubleshooting and scope picyures of good/bad
Some of you may call me crazy, but the way technical eduction is becoming watered down in the basic aspects of engineering siuch as absence of electromagnatism and measurement theory education, the reliability of electronic systems will be greatly challenged.
Hmm, I can neither hear any audio nor see any activity (slide-show in the browser). Can open the stand-alone Power-Point, though. Thanks for posting the page# of the slide in the chat area.
i hear what u all are saying. Most people are having no probs and audio is fine. If you really can't hear or get the PPTs, this show will be available as an archive later today (if it's not working at work, try it at home tonight).
A: put a resistor around 68 ohm to input th LM 7805. Conect Emiter of a PNP transistor to left side the resistor, then Bese to right side of resistor or regulator input. And colector to output of regulator. Pass around 100 mA throuth the resistor causes 0.7 v drop the on resistor and also emitter- base of trsnsistro. Result, any current pulling from regulator will be pass from transistor ont regulator. Up to 5 A you an pull regulated 5 v from this circuit.
The speed kills slides reminds me of "real time" troubleshooting challenges. Static testing with a logic probe may not see the problem, scope may look "OK". I found that looking through the analog world with a Huntron Trackerf worked for real world speed problems with wounded chips and damaged terminators.
The streaming audio player will appear on this web page when the show starts at 2pm eastern today. Note however that some companies block live audio streams. If when the show starts you don't hear any audio, try refreshing your browser.
@Jack - any info on the cost of "Micro Digital's GoFast" ? Their website is slick but deliberately omits pricing. Leads me to believe it is very expensive.
@simona - The chat will appear right here as you've written. The radio player will open up on this page at the set time for the show. In advance of the show you can download Today's Slide Deck to follow along with the lecturer. We look forward to chatting with you right here!
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