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.

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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. 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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Accept Cookies. Cookie Settings. Privacy Preference Centre Active. Save Settings. Allow All. ST Community. 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.

Microsecond delay in STM32

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.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.

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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.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.

stm32 dwt

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?

Разработки на микропроцессорах. Иногда малость бесит. STM32. CooCox

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.

stm32 dwt

The answer is: we need a hardware timer. And we have several options. The first one comes from the previous tests. So, we can use this special unit available in STM32 to count the number of cycles performed by the MCU during instruction execution. How much precise this function is? The best performance is achieved when the higher compiler optimization level is set. Why this function is not so precise?

However, the advantage of this function is that it automatically detects CPU speed, and it works out of the box especially if we are working on faster processors.

This is the most optimized way to write the while counter-- function. However, this macro has to be rearranged if you processor speed is lower, and keep in mind that being a macro, it is "expanded" every time you use it, causing the increase of firmware size.

If you think that other solutions can be better than these ones, feel free to comment below this post. Tags 1us delay gcc microsecond spin stm Doesn't the actual time also depend on whether the instructions are cached or not when they are called? Yes, it depends also on pipeline cache.

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Better option could be using static inline function where function will be placed directly inline without calling it directly. I was able to create any size pulses with 20s variance with minimum size of ns.In this tutorial, I am going to show you how to create 1 microsecond delay in STM We will be using one of the Timer to do so.

The process will be same for all the STM32 devices, you need to make some minor changes though. This is the most important part of this process, so read this section very carefully. First of all we need to decide which Timer to use for the process.

There is no special requirement, just choose any one. I will be using timer 1. This is a very important piece of information, and you should know it about the timer that you are going to use. As shown in the picture above, first of all you have to enable the clock source as internal clock.

Prescaler divides the Timer clock further, by the value that you input in the prescaler. And for this reason, the prescaler value is The ARR i am setting is the max value it can have. Basically, the counter is going to count from 0 to this value.

Every count will take 1 us. So setting this value as high as possible is the best, because this way you can have large delays also. I have set it to 0xffff-1and it is the maximum value that a 16 bit register ARR can have. I have also enabled the pin PA1 as outputso that we can see the result in an oscilloscope. Now, we will write a function to create this 1 us delay. Below is the one. When the function is called with the parameter as the number of microseconds, the following operations takes place.The DS18B20 digital thermometer provides 9-bit to bit Celsius temperature measurements and has an alarm function with non-volatile user-programmable upper and lower trigger points.

It will be included in the code when you download it below. We need to write few functions for the sensor. They are as follows. In order for the sensor to work, we need to initialize it every time. Here is the function for that. To write a BIT to the sensor, we need to perform some operation on the data line. After the master initiates the read time slot, the DS18B20 will begin transmitting a 1 or 0 on bus.

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It transmits a 1 by leaving the bus high and transmits a 0 by pulling the bus low. When transmitting a 0, the sensor will release the bus by the end of the time slot, and the bus will be pulled back to its high idle state by the pullup resister.

The following is the sequence for reading temperature from the ds18b No comments:. Subscribe to: Post Comments Atom. Search This Blog.

DHT11 sensor with STM32

Follow by Email. Report Abuse. Popular Posts. Connecting HC in Master and slave mode. Today I am going to int Total Pageviews. Powered by Blogger.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. Enables LSU count event.

Enables Sleep count event. Enables Interrupt overhead event. Enables CPI count event.

stm32 dwt

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.

stm32 dwt

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. 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.

HAL library 3- DELAY for STM32Fxxx

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. This means that sleep duration must be calculated with the frequency of FCLK during sleep.

Cycle Counting on ARM Cortex-M with DWT

LSU counter. This counts the total number of cycles that the processor is processing an LSU operation. The initial execution cost of the instruction is not counted.

For example, an LDR that takes two cycles to complete increments this counter one cycle. Equivalently, an LDR that stalls for two cycles and so takes four cyclesincrements this counter three times. This counts 1 for each instruction that takes 0 cycles. If the core is not in debug state, the value returned is the instruction address of a recently executed instruction. However, the actual comparison is slightly more complex to enable matching an address wherever it appears on a bus.

So, if COMP is 3, this matches a word access of 0, because 3 would be within the word. Each comparator can:. Match against either the PC or the data address. Perform data value comparisons if associated address comparators have performed an address match.

This bit is only available in comparator 1.


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