rtos

I am using an MSP430f5438 with version 5.4 of FreeRTOS. I am having a funny problem that I can't figure out. Basically, when I set configTICK_RATE_HZ to different values, the LED blinks faster or slower; it should stay the same rate. It blinks slower the higher i set configTICK_RATE_HZ, and faster when I set TICK_RATE lower. vTaskDelayUntil( &xLastFlashTime, xFlashRate ); is such that the LED should only blink once a second no matter what the configTICK_RATE_HZ is. I stepped through and checked the xFlashRate to make sure. Its always = to the configTICK_RATE_HZ. Code: xFlashRate = ledFLASH

Trying to make my generic Ubuntu to real time Ubuntu by modifying the kernel by patching / installing RT Linux but couldn't find a straight setup. Can someone help with the steps? Step 0 - Make a working directory Make a working directory #Move to working directory mkdir ~/kernel && cd ~/kernel Step 1 - Download kernel and patch Go to https://www.kernel.org/pub/linux/kernel/ and download a desired version of kernel to ~/kernel. Similarly, go to https://www.kernel.org/pub/linux/kernel/projects/rt/ and download the RT patch with same version as the downloaded kernel version. The kernel and patch

Who schedules the scheduler? Which is the first task created and how is this first task created? Isn't any resource or memory required for it? isn't like a chicken and egg scenario? Isn't scheduler a task? Does it get the CPU at the end of each time slice to check which task needs to be given CPU? Are there any good links which makes a person think and understand deeply all these concepts rather than spilling out some theory which needs to be byhearted? The scheduler is scheduled by an (external) event such as an interrupt, (disk done, mouse click, timer tick) or an internal event (such as the

I was reading this article, but my question is on a generic level, I was thinking along the following lines: Can a kernel be called real time just because it has a real time scheduler? Or in other words, say I have a linux kernel, and if I change the default scheduler from O(1) or CFS to a real time scheduler , will it become an RTOS? Does it require any support from the hardware? Generally I have seen embedded devices having an RTOS (eg VxWorks, QNX), do these have any special provisions/hw to support them? I know RTOS process's running time is deterministic, but then one can use longjump

When should one use polling method and when should one use interrupt based method ? Are there scenarios in which both can be used ? If the event of interest is: Asynchronous Urgent Infrequent then an interrupt based handler would make sense. If the event of interest is: Synchronous (i.e. you know when to expect it within a small window) Not Urgent (i.e. a slow polling interval has no ill effects) Frequent (i.e. majority of your polling cycles create a 'hit') then polling might be a better fit. Other considerations include whether you are writing a device driver for an OS or just writing bare