Microcontroller Central - Tracking Down Real-Time

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Comments Tracking Down Real-Time Newest First Oldest First Threaded View [close this box] << < Page 3 / 3 Robotics Developer 2/9/2012 6:21:08 PM User Rank Program Manager Re: What about multiple definitions? The question of "What is Real Time?" has been quite a problem for control and robotic systems. All too often, an OS is advertised as "Real Time" when the truth is far from it. While the definition may vary based on the system needed response times, I like to use the concept of Repeatability. If the OS can guarantee the repeating of code blocks in the same period / time frame then it "could be" considered "Real Time". I use this concept to address the various issues of speed to process, lag and response times, interrupt overhead, etc. A simple multi-tasking OS is not real time unless there is a fixed scheduler with enough processing capacity to service all the needed tasks without interference with the others. I am sure that there are better definitions and would welcome them for review. Reply Post Message Messages List Start a Board Login 50% 50% duanebenson 2/9/2012 5:30:30 PM User Rank Blogger What about multiple definitions? Take an extreme case like the attempt to drop power in a motor control before a spike blows up your MOSFETs. The rest of the circuit might just be responding to button presses, variable resistors, water pressure sensors and such; something where real-time could be measured in a few tens of milliseconds. The current spike protection might need to respond much faster than that. One might run the current sense into a GPIO of the MCU thinking that an interrupt on change could be used to drop or cut the power before any damage is done. First though, there's the delay in the current sense hardware. Then the read time for the port, the ISR delay and then into the code to take the action. Such a scenery might require external hardware that has the greater real-time speed than is possible within the RTOS or even a MCU without any type of OS. Reply Post Message Messages List Start a Board Login 50% 50% << < Page 3 / 3		latest blogs Safe MCU Design: Testing MCUs for Class C 3 comments In the last of a series on safety-related design, Ryszard discusses the unique features that Class C safety testing requires. Come Chat About Discussion Groups 1 Comment We need to talk about setting up discussion groups on the site, so I've set up a live chat for Friday. MCU Low Power: What Does the Future Hold? 36 comments Warren concludes his discussion of MCU low-power modes with a look at the possibilities for next-generation design. Simple Windows Programs Support MCU Audio Test 9 comments Curt offers the community an audio generator and recorder for the PC that he uses to test data acquisition and processing in an MCU. Help Define MCC Discussion Groups 17 comments If you think MCC needs some traditional discussion groups, come help set them up. More Blogs information resources sponsored content by NXP ARTICLE - LPC800 Switch Matrix: Making life easier one pin at a time ARTICLE - LPC800 Low Power Features ARTICLE - Making Motor Control Easy with Low Cost fully feat ARTICLE - First thoughts on NXP's New M0 LPC800 mcus BLOG - An1339 Li-On Charger with the LPC111x a multi-tasking approach to battery refreshes BLOG - Teach your MCU to talk An11085 Speex on LPC175x6x BLOG - emwin skins BLOG - How to invoke ISP mode LPCxpresso LPC812 board BLOG - LPC800 expresso board jlink ulink or ulinkme connection BLOG - mbed New networking stack All resources flash poll All polls MC on twitter Follow us like us on facebook