Stm32 ll delay


  • Library 03- STM32F4 system clock and delay functions
  • STM32 Delay Microsecond Millisecond Utility | DWT Delay & Timer Delay
  • nanoseconds delay
  • STM32 delay ms function
  • Working with STM32 and Timers part 1: Delay using Timer
  • Basic systick configuration on the STM32
  • Bare-Metal STM32: Blinky And The Secret Of Delay Functions
  • Library 03- STM32F4 system clock and delay functions

    Feel free to have a look at it if you need a refresher, though. Our focus will be on the Timer module instead, the way its delay function is implemented, as well as the two alternate approaches. The Low-Tech, Active Delay A completely serviceable, functional, and reasonably accurate delay feature can be implemented in a bare-metal environment using nothing more than a humble while loop.

    This exploits the discrete nature of processor cycles in combination with knowing the current system clock.

    Essentially this means converting the desired delay to processor time and counting down or up to that interval. Naturally, each iteration of the while loop takes more than one clock cycle, so we then have to divide the number of clock cycles by the duration of a loop iteration. As with many things in life, when something is this easy, it has to come with a whole list of gotchas.

    First and foremost is its lack of accuracy. The moment a single interrupt occurs e. The fact that this is an active delay, which fully occupies in other words blocks the processor further means that it does not work for a multitasking environment. In effect, this is the kind of delay function you really only wants to use as a quick-and-dirty throw-away function during testing or debugging.

    Counting SysTicks The Cortex-M core has a few standard peripherals as well that are integrated directly into this core. Of these, NVIC is as the name implies essential for registering and handling interrupts. The SysTick timer is a fairly simple timer, which can essentially count down from the set value to zero. As we saw in the Blinky example code, we first create an instance of the Timer class.

    This sets up a few items in the constructor of the Timer class: This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.

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    STM32 Delay Microsecond Millisecond Utility | DWT Delay & Timer Delay

    How should you ask your chip to do something on a schedule? In this tutorial, we will write code to enable a hardware interrupt triggered by a timer peripheral, and use that to blink an LED. As usual, an example project demonstrating this code is available in a Github repository. The F0 and L0 lines have slightly different clock configurations, but I will highlight those differences when they come up. Clock Sources The core clock signal is what drives the program logic on a microcontroller.

    Every time that the clock signal switches between a high and low signal level, an instruction can be run by the processor. This is similar to the sort of memory used in USB thumb drives, and it sounds like the chips can reliably read data from it at a maximum speed of about 24MHz. For MHz, we need to use at least 1 wait state. For MHz, at least 2 wait states are required. This fetches a handful of instructions at once from the Flash memory, to blunt the impact of waiting on the 24MHz flash memory access.

    The STM32L0 line is a bit different, but it mostly has the same core options. Frequency Multiplication and Division To get a specific frequency out of the Phase-Locked Loop peripheral, we need to tell it a few things about the signal that we want to generate: What clock source should the PLL use for its base signal?

    Which Clock Source? That might sound like a complicated process. The timer peripherals can perform a variety of time-based actions, and there are good explanations in the reference manuals. The first step is to enable the peripheral in its RCC register. It counts up from 0 once the timer is started. An autoreload value of N will cause the timer to trigger an update event every time the CNT register counts up to N.

    You can start a timer for the time that you want to delay, wait for a variable to be set in the interrupt handler, and then stop the timer. As usual, an example project demonstrating the code in this tutorial is available on Github. It seems like a good way to run recurring logic on a schedule, and I think that it might be a common way for RTOS systems to drive schedule timings.

    nanoseconds delay

    System Clock Frequency By far the hardest part of the whole process is determining the actual clock frequency of your processor. Clock setup on the ARM cores is pretty involved. Perhaps the easiest way to do it is to use the tools from ST. In a typical standard project setup the startup code will call the SystemInit function for you and, by the time your program gets control, the clocks are all set up and running.

    STM32 delay ms function

    You may think, at that stage, that you know what the clock frequency is but you should avoid referring to it by numerical value. Not only are magic numbers a Very Bad Thing in your code, if you make a mistake, the error can be hard to find.

    Fortunately the peripheral drivers provide a handy way to get the current value of the HCLK and use it in your calculations without having to know what it is. The trick then is to proceed with the systick configuration and set up some test code that will tell you immediately if you have it right.

    Working with STM32 and Timers part 1: Delay using Timer

    For this purpose, I like to just flash an LED once per second. It is soon apparent if the calculations are wrong. Something like this should probably be the first thing you run on a new board. First and foremost is its lack of accuracy.

    Basic systick configuration on the STM32

    The moment a single interrupt occurs e. The fact that this is an active delay, which fully occupies in other words blocks the processor further means that it does not work for a multitasking environment. In effect, this is the kind of delay function you really only wants to use as a quick-and-dirty throw-away function during testing or debugging. Counting SysTicks The Cortex-M core has a few standard peripherals as well that are integrated directly into this core.

    Of these, NVIC is as the name implies essential for registering and handling interrupts.

    Bare-Metal STM32: Blinky And The Secret Of Delay Functions

    The SysTick timer is a fairly simple timer, which can essentially count down from the set value to zero. As we saw in the Blinky example code, we first create an instance of the Timer class. This sets up a few items in the constructor of the Timer class: This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below.


    Stm32 ll delay