Stm32 dwt

Delay functions are needed in your program, no matter how optimized and fast program you wanna do. Milliseconds based delay is done using systick timer which makes interrupts every 1ms generated by HAL library. For microseconds based delay, DWT cycle counter is used to get maximal optimized delay. Library supports software timers generation. Software timer has resolution of 1ms and counts down. It can be used to generate events each X milliseconds in your project. Read more about new HAL libraries.

Tags: abstraction delay driver functions HAL hardware hardware abstraction layer layer software stm32 stm32f stm32f0 stm32f4 stm32f7 swtim timer. Owner of this site. Application engineer, currently employed by STMicroelectronics. Exploring latest technologies and owner of different libraries posted on Github.

View Results. Software timers Library supports software timers generation. Delay example 1. Delayms. Delay.

DHT11 sensor with STM32

Delay software timer. Delay example for time. Download all libraries. Read before commenting! Before you make a new comment, make sure you agree with things listed below: - Read post to make sure if it is already posted what you are asking for, - Make sure you have the latest version of libraries used in your project, - Make a clean and grammatically correct written message, - Report as many details as possible, including what have you done so far, - Do NOT post any code here.

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Cycle Counting on ARM Cortex-M with DWT

Enter relevant keywords and click the Search button View This Post. Posted on December 08, at Hi i have seen the below code on this forum. Can anyone help?. The bit nature will limit you to about I'm not sure it's entirely appropriate for 10 second delays, but could be modified to implement a timeout.

For 10 seconds, it would perhaps be better to use a slower timer and an interrupt so you're not grinding the processor in a loop doing nothing. This question is closed.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. 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.

From what I've seen online this should suffice for enabling it:. However, when ever I run that code the values are not changed or the operations are skipped I am not too sure what is happening. I've tried making pointers to the addresses in memory and altering them directly with no avail either. Aside from that though, I cannot seem to get the value to change in code. Edit: What could be causing the behavior where these lines of code are not performing their tasks but also not crashing and continuing.

stm32 dwt

After running these lines of codes, all of the values at those memory locations stay the same and are not altered with the operations that were supposed to be performed. Before After. You have to enable the trace module, too. Caution the code is not interrupt-safe! In general, you should leave the counter just free running and take differences of snapshots for timing.

Just make sure your toolchain does not use interfere with your code. As I already emphasised in the comments: Don't use some homebrew definitions for registers. More information can be found in the "Architecture Reference Manual". Caution: there is also an "Architecture Application Level Reference Manual", which is not what you want. You are doing everything right, except you are missing to unlock access to DWT register as Howard pointed out.

In your code it would be something like:. DAP access is always allowed that's why you could enable cycle counter using the debugger. Learn more. Asked 4 years ago.

Active 1 year, 9 months ago. Viewed 16k times. KenQueso KenQueso 1 1 gold badge 1 1 silver badge 6 6 bronze badges. Don't define your own registers. The definitions will generate much more code, as you define the pointers as variables.

Don't even think ybout const qualifier, they will be still variables. Well I've stepped through it and the operations look like they are occurring, but the values do not change for any memory location I want to edit. I have tried to find out without much avail so I figured the logical next step was to ask. Should work according to this.That is, how to measure microseconds precisely in STM32? The answer is: there are several ways to do this, but some methods are more accurate and other ones are more versatile among different MCUs and clock configuration.

This micro is able to run up to 84Mhz using internal RC clock. But how to establish how many clock cycles are required to compute one step of the while cycleCount-- instruction? Unfortunately, it's not simple to give an answer. Let's assume that cycleCount is equal to 1. How is it possible that? So that instruction has a "basic cost" of 24 cycles. How many cycles are required if cycleCount is equal to 2? In this case the MCU requires 33 cycles, that is 9 additional cycles.

So, we can write our delay function in a more general way:. Don't forget that even a simple procedure call, without parameter passing, costs CPU cycles due to branching and invalidation of cache pipeline. The answer is NO. If you decide to use a different clock speed, you need to rearrange it doing tests.

Second, it is subject to compiler optimizations. Let's now enable GCC optimization for "size" -Os. What results do we obtain? The scope confirms this:. And what happens if we enable the maximum optimization for speed -O3? Having said this, the fact remains that if we want use a lower CPU frequency or we want to port our code to a different MCU we need to redo tests again.Your browser has JavaScript disabled.

If you would like to use all features of this site, it is mandatory to enable JavaScript. For this, I am using the following code. C Source Code. Hi, Your code looks correct. Usually the cycle counter is already enabled after start, but it does not hurt to re-enable it. In the status bar of Embedded Studio you can see the cycle counter, too as xxx,xxx Cycles. You could check if it is running there.

Regards Johannes. Hi Johannes. Your code looks correct. Hi, The status bar shows the value as read from the cycle counter. I tried the same in Embedded Studio. The status bar showed 0 and increased and the printf worked accordingly. Hi Johannes, I cannot reproduce the counter to be working. I have a minimal not-working example in the attachment. After the print loop, the program reads the current DWT counter and prints it. I would expect this to print the current value as seen from the status bar.

However, this prints: "Count is 0". Furthermore, resetting the counter does not work for me. Can you verify this with the solution project provided? Hi, The sample you provided runs in the simulator, which does not simulate the DWT. Hi, Oh, that is the culprit. Is there a possibility to use the DWT cycle counter or any other counter in the simulator? Best, Razer6. Hi, The only peripheral which is simulated is the SysTick.

Everything else can only be used on hardware. As per my knowledge you should enable it again. In the status bar of Embedded Studio you can see the cycle counter.

Facebook 0 Twitter 0 Google Plus 0 Reddit 0.Enables Cycle count event. Enables Folded instruction count event.

A folded instruction is one that does not incur even one cycle to execute. For example, an IT instruction is folded away and so does not use up one cycle.

stm32 dwt

Enables LSU count event. Enables Sleep count event. Enables Interrupt overhead event. Enables CPI count event. Enables PC Sampling event. No synch counting. That counter then counts down. When the selected tapped bit changes from 0 to 1 or 1 to 0, the post scalar counter is down-counted when not 0. For example, a value 1 in this register means an event is formed every other tap change.

This count can measure elapsed execution time. When enabled, this counter counts the number of core cycles, except when the core is halted.

Applications and debuggers can use the counter to measure elapsed execution time.

Mastering RTOS Debugging Techniques

By subtracting a start and an end time, an application can measure time between in-core clocks other than when Halted in debug. This is valid to 2 32 core clock cycles for example, almost 86 seconds at 50MHz. Current CPI counter value. This counter also increments on all instruction fetch stalls. Current interrupt overhead counter value.

Counts the total cycles spent in interrupt processing for example entry stacking, return unstacking, pre-emption. An event is emitted on counter overflow every cycles. This counter initializes to 0 when enabled. It is possible that the frequency of FCLK might be reduced while the processor is sleeping to minimize power consumption.The STM32 turns the one-architecture-fits-all concept into reality.

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stm32 dwt

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