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It is stuck in this function:. So I stucked in this loop. Why systick interrupt not works? Check also if other Interrupts are working, and that SysTick Handler is present. Probably because you're blocking in a callback? I call this function in while in main when I cut transmission again stuck All rights reserved STMicroelectronics.Cookie Notice.
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It's what I did e. Thanks again for those explanations. Yes, I did try your solution but it does not work for me. Did you initialize it by yourself to that value, and in that case how are you sure there are no side effect? From port. If Systick prio was set to 5 and my driver interrupt set to higher value than 5 lower prio then I think that both your proposed solution and the ST provided HAL driver timeout would work.
Regarding another possibility I did already protect the I2C driver with semaphores and queues to make them RTOS safe for my application. And to your question '' But who would insert delays in an interrupt handler anyway? All rights reserved STMicroelectronics. Cookie Notice Cookies and similar technologies enable us to provide you with an optimized user experience and functionality of our website.
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Save Settings. Allow All. ST Community. Enter relevant keywords and click the Search button View This Post. With systick priority set to lowest priority the HAL driver hangs instead of timing out. It would fail if i get event that would have higher priority than systick. In the first place, and in fact the route cause of the problem, a driver is supposed to be short lived.
The driver should never poll waiting on an event. Instead of polling it should just exit and let an I2c driver wait for the relevant interrupt. Doing so would return the processing to user level code allowing low priority drivers to execute and likely letting RTOS do its job.In return for using our software for free, we request you play fair and do your bit to help others! Sign up for an account and receive notifications of new support topics then help where you can.Code to rotate button phone screen
Use these archive pages to search previous posts. This of course only works if the tick interrupt has a higher priority than the active interrupt. It even states that multiple times in the source code port. There is therefore no need to save and then restore the interrupt mask value as its value is already known.
But is this a save way to go? Thanks for your help! This has been raised a few times before. First the FreeRTOS tick and PendSV handlers must have the lowest possible interrupt priority because that assumption is made when the tick handler enters and exits a critical section — rather than setting the basepri register back to whatever value it had when it exits a critical section it assumes basepri was clear and just sets it to zero.
If the SysTick is running at the lowest priority then this assumption is safe, as the SysTick would only execute in the first place if basepri was clear any other value would mask the interrupt out.
Now you can edit the FreeRTOS source code so the SysTick saves and restores the basepri register rather than just blindly setting it and then clearing it back to zero — that will come with the overhead of more asm instructions and more memory accesses on every tick interrupt though.
If so, that would imply other interrupt service routines were somehow busy waiting, which is not good in an ISR, and not needed if you are using an OS anyway.
Thank you for your answer! HAL tick needs to be at the highest priority not necessarily the highest priority. Only higher than interrupts calling the HAL library.Cinebench cpu benchmark
Timeout values are hardcoded in HAL lib and are in the range of I wanted to see if communication errors are reported correctly and simulated an error by shorting the I2C wires. This construct exists many time within the HAL lib source code. Your system is not going to be real time if interrupts loop for 10s of ms.
I doubt the function this line is in is meant to execute in an interrupt. Context switching is performed in the PendSV interrupt. Pend the PendSV interrupt.
STM32F103 SPL Tutorial 4 – Create a Delay Function with System Timer
The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. I'm currently auditing an online edX course about embedded systems, and learning about using the SysTick timer to calculate elapsed time.
Picture of logic I'm referring to. Code of logic I'm referring to. However, there is one point that is confusing me. I understand the idea of subtracting "now" from "last" to get the elapsed time. The value is being stored in an unsigned long, so does it break the program? Or does this just never happen, and if so why? I would appreciate any help on clearing this up! I looked at the only other link I could find that was similar to my question here: How to deal with a wrapping counter in embedded C but I didn't find a clear answer to my question from that.
So counting up or down doesnt matter, you just need to adjust the operands correctly. So say counting down 7,6,5,4 7 - 4 is 3 counts. Should be simple to write a program for a 4 or 5 bit counter try random sized counts. Or use fixed sized counts allowing for roll over using prime numbers. This ONLY works if it is a counter that rolls over from all zeros to all ones or all ones to all zeros depending on the direction.
I would hope it obvious if you set a hypothetical 3 bit timer to start at 5 and it rolled over from zero back to that 5 set point then three steps could be 1,0,5,4 and is not 3. Another way to think of this is yet another feature of twos complement, near the wraparound point.
It is just like the number line we used in grade school. Basically using the beauty of twos complement and we know that addition and subtraction in binary thanks to twos complement is not unsigned or signed specific the same bit patterns result in the same bit patterns. It is just how we interpret them. So we are cheating a little, taking signed math and interpreting the result as unsigned. There is a simple solution to calculating the difference between two integers that are not the same size as any standard integer types.
You simply shift the integer so that its MSB is in the MSB position of a standard type, perform the arithmetic, then optionally shift the result back so that it is in the same units as the original values. Note the order of the operands - systick counts down. This assumes that you are setting the maximum reload value of 0xffffffand that systick does not wrap more than once.
If the time intervals are such that the counter may wrap more than once, then you might not need such high resolution, and could perhaps use a lower reload value and an interrupt handler that increments a counter, and use that lower resolution counter for time measurement.As we will see below, this tick drives the context switch between tasks.
But first, what drives this tick? At the simplest level, the tick is just a timer that has a period set to match the desired tick rate. By default, this is set to 1ms which provides a good balance between task speed and overhead of task switching.
The timer interrupt is triggered every time the period is hit. This timer is called the SysTick System Tick and provides its own clock configuration, counter value, and interrupt flag. But as we will look at in future posts, we can utilize the flexible nature of what drives the FreeRTOS tick to reduce power. You can check out the links provided to get a review of these multitasking models. FreeRTOS allows for both models, but our discussion on the tick makes more sense in the preemptive mode.
When the operation system is running, each of these tasks exists in one of four states:. The diagram below shows a basic example of three tasks switching context either due to priority interrupt or context switching during the tick.
Higher priority tasks higher number in FreeRTOS are immediately switched to if they become unblocked due to a semaphore or queue releasing them and the next task takes over if any task goes into the blocked state waiting for a semaphore or queue. If multiple tasks are the same priority and are always in the Running or Ready state, the kernel creates a Round Robin model where each gets a full tick before switching to the next. This Round Robin mode is where the balance between how fast the System Tick should be.
A faster tick would allow more tasks to do operations in a given timeframe, but each task will only be able to do a limited amount of work before having to stop.
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While the FreeRTOS tick function generally is switching context between equal priority tasks, it could also cause tasks to go from the Blocked to the Ready state, potentially moving a higher priority task into the Running state. In part, this happens because tasks are generally setup to react to certain events, events that may not happen often. Between waiting for the next event, it could be that all of your tasks have nothing to do and have entered the Blocked state.
Otherwise, the idle task is where you do low priority tasks like diagnostics or logging. This code could be called by the idleTaskHook function inside the Idle task, or creating tasks that are set to the idle priority of 0. What we will get into later is looking at how long we need to wait for the next task to be serviced or times out waiting.
We can use this information to decide to go into lower power states to conserve battery life or improve power efficiency. At the simplest level, the ARM call to WFI will put the processor on hold until the next interrupt kicks it back into gear. This saves a small amount of current as the core processor clock is disabled until the next FreRTOS tick. If you want to make sure you notified of these upcoming posts, sign up for our weekly newsletter below.SysTick is a basic countdown timer.
SysTick can be polled by software or can be configured to generate an interrupt. To use SysTick, we must load a value to the reload value register. In this tutorial, I will explain how to use SysTick for creating a delay function. SysTick can be configured through the registers below. This function will initialize SysTick and its interrupt, then start the SysTick.
The counter is in free running mode to generate periodic interrupts.C++ button styles
The input parameter of this function is the number of ticks between two interrupts. There is a variable called usTicks that holds the value of ticks in us. Every time we call DelayUs function, we should load this variable with the delay value in us and then we poll this variable until reach 0.
To create DelayMs function, we should load the delay value in ms, then it will be decremented by 1 every us using DelayUs function. This is the code for delay library. To use the delay functions, you should call the DelayInit function first. For the project file you can get it from here. Go to the part 5 of the tutorial. Your email address will not be published. All source codes included. Include file delay. Source file delay. SystemCoreClockUpdate. DelayUs. Leave a Reply Cancel reply Your email address will not be published.Rel t5i vs t7i
Of course to convert from ticks to milliseconds I need to know how many ticks are in a millisecond, and it's CPU specific. My real problem is knowing how to measure time in microseconds. This is addressed in the comments and at least in one of the answers so I'm mentioning this here too and I edited the title. How do you achieve it is up to you. You can e. And it would still be a horrible waste of precious processor cycles unless you do something in the handler that a hardware counter can't.
Getting back to your real problem, measuring time in the order of microseconds, there are better ways.Odroid c2 specs
If you have a bit timer available, then you can put the MHz value of the respective APB clock in the prescaler, start it, and there is your microseconds clock, not taking away processing time from your application at all. Check your reference manual which hardware timers have bit counters, and where does it get its clock from. It varies a lot across the whole STM32 series but should be there on an F4.STM32F4 Tutorial: LED toggle using Systick timer (IAR IDE)
Note that as it returns the elapsed processor cycles, it will overflow in a couple of seconds. I've just noted that you're using an STM32L0. You could post it as a separate question, describing in more detail how your hardware looks like and what it should it do.
It's both. Most of the time the function which increments the HAL tick counter is hooked to SysTick interrupt, which is configured to tick every 1ms. This can also be though of as "the number of times the SysTick interrupt has 'ticked'". Here's what I came up with. I did not fully explore why I had to do what I did. But I realized two things very quickly. This was one of several things I tried to get it to work basically a half-us clock, and divide the result by 2.
I tried several unsuccessful things to stop, reprogram and restart it, and setting the count to was a crude but effective way to just let it complete its current cycle, then very quickly start working as desired. There are certainly better ways of achieving this.
But overall this is a simple way of getting an accurate event timestamp with very low overhead. Learn more. Asked 3 years, 1 month ago.
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