One way to test the debounce algorithm is to pick a low cost development kit, such as an STM32 Nucleo board, and write some application code that will debounce the onboard button and turn an LED on. Spending a little bit of time up front to think through an API, select an implementation and flowchart the design will save more time on the back-end then the upfront investment. These steps have demonstrated how a reusable button algorithm can be developed but these same steps and strategies can be applied to nearly any component that a developer would use or develop for an embedded system.
These are good …. Much more flexible, reusable and documented and easier to read! To be sure, my perspective is that debounce routines are used equally as much on noisy digital inputs as they are on actual physical switches… assume there could be some noise on the signal in both logic states, as well as during transitions. Flow chart could be amended by having separate press and release debounce counters.
As Jacob pointed out in first comment, this is just a kick-off. Your email address will not be published. Save my name, email, and website in this browser for the next time I comment. Notify me of follow-up comments by email. Notify me of new posts by email. This site uses Akismet to reduce spam. Learn how your comment data is processed. The code is fairly straightforward and all functions we use are from previous projects. The sketch reads the current state of the input button while keeping track of the state of the button from the previous loop of the main program.
The sketch then increments a counter variable and outputs that value to the serial port. You can view this count through the serial monitor window. Ideally, the sketch would increment the counter variable every time you press the button.
However, after a few button presses, you will start to notice that sometimes the counter variable will increment multiple times. In other words, you will press the button once, but you will see more than one counter value printed to the serial monitor. This happens because the program sketch has detected multiple rising edges in very close succession this occurs because of a button bounce.
This code is extended to provide a button press counter capability by counting rising edges to verify the code is operating correctly. The debouncing algorithm used for this sketch at first may appear slightly different than our theoretical explanation, but once examined you can see the differences are only marginal. When analyzing the debouncing algorithm used for our sketch, we only look at the point when the input signal changes as opposed to taking a periodic time sample like our theory explanation suggested.
Now if the input signal doesn't change and the set time has elapsed, then it means that point A and point A -1 have the same value. If they were different, the algorithm would have already reset itself.
Toggle Navigation. Table of Contents. Forgot Your Password? Forgot your Username? Haven't received registration validation E-mail? User Control Panel Log out. Forums Posts Latest Posts. View More. Recent Blog Posts. Unread PMs. Forum Themes Elegant Mobile. Essentials Only Full Version. Starting Member. Debounce algorithm Hi, I have found Kenneth A.
Kuhn's debounce algorithm on the web and I like the algorithm he is using. The processor speed I want to use is 16MHz. I want to convert his C code into Assembler. I have no knowledge of C but I do am following some C courses on the web, so I think I know how to convert the C code into pseudo code and them make the translation to assembler. Since with 16MHz, the maximum amount of time I can use is 0,ms for each interrupt.
With a value of loaded into TMR0, I can count to a maximum of 0,ms If I sample a maximum number of times the maximum debounce time I can vreate is 16,38ms. WAY to short for a debounce sample time I also would like to know if I can easily adapt this code for a whole port PortB instead of just one input.
Which is what this original code is for, I think. Anybody some thoughts about it??? Super Member. Did you forget about the internal PLL? See the section "6. Actually, TMR2 is better for regular interrupts. With a value of loaded into TMR0, I can count to a maximum of 0,ms Why set the prescaler to ?
That can be accomplished with a resistor that pulls the port pin in one direction when the button is open. We can choose an active high or active low configuration. Since AVR has an internal pull-up resistor, we usually choose the active low configuration shown on the left in the figure. We can skip the external resistor and activate internal pull-up instead. If we want to toggle a LED on or off every time a button is pressed, we can try this small program.
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