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//! # Debouncr //! //! A simple and efficient `no_std` input debouncer that uses integer bit //! shifting to debounce inputs. The algorithm can detect rising and falling //! edges and only requires 1 byte of RAM for detecting up to 8 consecutive //! high/low states or 2 bytes of RAM for detecting up to 16 consecutive //! high/low states. //! //! The algorithm is based on the [Ganssle Guide to //! Debouncing](http://www.ganssle.com/debouncing-pt2.htm) (section "An //! Alternative"). //! //! ## API //! //! ### Instantiate //! //! First, decide how many consecutive logical-high states you want to detect. //! For example, if you poll the input pin every 5 ms and require 4 //! consecutive logical-high states to trigger a debounced press event, that //! event will happen after 20 ms. //! //! ```rust //! use debouncr::{Debouncer, debounce_4}; //! let mut debouncer = debounce_4(); // Type: Debouncer<u8, Repeat4> //! ``` //! //! ### Update //! //! In regular intervals, call the `update(pressed)` function to update the //! internal state. //! //! ```rust //! # use debouncr::{Debouncer, debounce_3, Edge}; //! let mut debouncer = debounce_3(); //! # fn poll_button() -> bool { true }; //! assert_eq!(debouncer.update(poll_button()), None); //! assert_eq!(debouncer.update(poll_button()), None); //! assert_eq!(debouncer.update(poll_button()), Some(Edge::Rising)); //! ```` //! //! The `update` function will return a rising/falling edge, or `None` if the //! input is still bouncing. //! //! ### Query debounced state //! //! You can also query the current debounced state. If none of the `n` recent //! updates were pressed, then the debounced state will be low. If all `n` //! recent updates were pressed, then the debounced state will be high. //! //! ```rust //! # use debouncr::{Debouncer, debounce_3}; //! let mut debouncer = debounce_3(); //! //! // Initially low //! assert!(debouncer.is_low()); //! assert!(!debouncer.is_high()); //! //! // Update, now it's neither high nor low //! debouncer.update(true); //! assert!(!debouncer.is_low()); //! assert!(!debouncer.is_high()); //! //! // After two more updates, it's high //! debouncer.update(true); //! debouncer.update(true); //! assert!(debouncer.is_high()); //! ``` //! //! ## Example: RTFM //! //! If you want to debounce a pin in an [RTFM](https://rtfm.rs/) project, //! register a resource and a timer. //! //! ```ignore //! use debouncr::{Debouncer, debounce_12, Edge, Repeat12}; //! //! #[app(..., monotonic = rtfm::cyccnt::CYCCNT)] //! const APP: () = { //! struct Resources { //! button: gpioa::PA11<Input<PullUp>>, //! button_state: Debounce<u16, Repeat12>, //! } //! //! #[init(spawn = [poll_button])] //! fn init(ctx: init::Context) -> init::LateResources { //! // ... //! ctx.spawn.poll_button().unwrap(); //! init::LateResources { //! button, //! button_state: debounce_12(), //! } //! } //! //! /// Regularly called task that polls the buttons and debounces them. //! #[task( //! resources = [button, button_state], //! spawn = [button_pressed, button_released], //! schedule = [poll_button], //! )] //! fn poll_button(ctx: poll_button::Context) { //! // Poll button //! let pressed: bool = ctx.resources.button.is_low().unwrap(); //! //! // Update state //! let edge = ctx.resources.button_state.update(pressed); //! //! // Dispatch event //! if edge == Some(Edge::Rising) { //! ctx.spawn.button_pressed().unwrap(); //! } else if edge == Some(Edge::Falling) { //! ctx.spawn.button_released().unwrap(); //! } //! //! // Re-schedule the timer interrupt //! ctx.schedule //! .poll_button(ctx.scheduled + POLL_PERIOD.cycles()) //! .unwrap(); //! } //! //! /// The button was pressed. //! #[task] //! fn button_pressed(ctx: button_pressed::Context) { //! // Button was pressed, handle event somehow //! } //! //! /// The button was released. //! #[task] //! fn button_released(ctx: button_pressed::Context) { //! // Button was released, handle event somehow //! } //! //! }; //! ``` #![cfg_attr(not(test), no_std)] #![deny(unsafe_code, missing_docs)] use doc_comment::doc_comment; /// The main debouncer instance. /// /// It wraps a `u8` or `u16`, depending on the number of required consecutive /// logical-high states. /// /// To create an instance, use the appropriate `debounce_X` function (where `X` /// is the number of required consecutive logical-high states). #[repr(transparent)] pub struct Debouncer<S, M> { state: S, mask: core::marker::PhantomData<M>, } /// Rising or falling edge. #[derive(Debug, PartialEq, Eq)] pub enum Edge { /// A rising edge Rising, /// A falling edge Falling, } macro_rules! impl_logic { ($T:ty, $count:expr, $M:ident, $name:ident, $mask:expr) => { doc_comment! { concat!( "Detect ", $count, " consecutive logical-high states.\n\n", "This type should not be used directly. ", "Instead, construct a [`Debouncer`](struct.Debouncer.html) through [`debounce_", $count, "()`](fn.debounce_", $count, ".html).", ), pub struct $M; } doc_comment! { concat!( "Create a new debouncer that can detect a rising edge of ", $count, " consecutive logical-high states.", ), pub fn $name() -> Debouncer<$T, $M> { Debouncer { state: 0, mask: core::marker::PhantomData, } } } impl Debouncer<$T, $M> { /// Update the state. pub fn update(&mut self, pressed: bool) -> Option<Edge> { // If all bits are already 1 or 0 and there was no change, // we can immediately return. if self.state == $mask && pressed { return None; } if self.state == 0 && !pressed { return None; } // Update state by shifting in the press state & masking self.state = ((self.state << 1) | (pressed as $T)) & $mask; // Query updated value if self.state == $mask { Some(Edge::Rising) } else if self.state == 0 { Some(Edge::Falling) } else { None } } /// Return `true` if the debounced state is logical high. pub fn is_high(&self) -> bool { self.state == $mask } /// Return `true` if the debounced state is logical low. pub fn is_low(&self) -> bool { self.state == 0 } } }; } impl_logic!( u8, 2, Repeat2, debounce_2, 0b0000_0011); impl_logic!( u8, 3, Repeat3, debounce_3, 0b0000_0111); impl_logic!( u8, 4, Repeat4, debounce_4, 0b0000_1111); impl_logic!( u8, 5, Repeat5, debounce_5, 0b0001_1111); impl_logic!( u8, 6, Repeat6, debounce_6, 0b0011_1111); impl_logic!( u8, 7, Repeat7, debounce_7, 0b0111_1111); impl_logic!( u8, 8, Repeat8, debounce_8, 0b1111_1111); impl_logic!(u16, 9, Repeat9, debounce_9, 0b0000_0001_1111_1111); impl_logic!(u16, 10, Repeat10, debounce_10, 0b0000_0011_1111_1111); impl_logic!(u16, 11, Repeat11, debounce_11, 0b0000_0111_1111_1111); impl_logic!(u16, 12, Repeat12, debounce_12, 0b0000_1111_1111_1111); impl_logic!(u16, 13, Repeat13, debounce_13, 0b0001_1111_1111_1111); impl_logic!(u16, 14, Repeat14, debounce_14, 0b0011_1111_1111_1111); impl_logic!(u16, 15, Repeat15, debounce_15, 0b0111_1111_1111_1111); impl_logic!(u16, 16, Repeat16, debounce_16, 0b1111_1111_1111_1111); #[cfg(test)] mod tests { use super::*; #[test] fn test_rising_edge() { // Initially not pressed let mut debouncer: Debouncer<u8, Repeat3> = debounce_3(); assert!(debouncer.is_low()); // Three pressed updates required assert_eq!(debouncer.update(true), None); assert_eq!(debouncer.update(true), None); assert_eq!(debouncer.update(true), Some(Edge::Rising)); // Further presses do not indicate a rising edge anymore assert_eq!(debouncer.update(true), None); // A depressed state resets counting assert_eq!(debouncer.update(false), None); assert_eq!(debouncer.update(true), None); assert_eq!(debouncer.update(true), None); assert_eq!(debouncer.update(true), Some(Edge::Rising)); } #[test] fn test_falling_edge() { // Initially not pressed let mut debouncer: Debouncer<u8, Repeat3> = debounce_3(); assert!(debouncer.is_low()); // A single non-pressed update does not trigger assert_eq!(debouncer.update(false), None); assert!(debouncer.is_low()); // Trigger a falling edge assert_eq!(debouncer.update(true), None); assert_eq!(debouncer.update(false), None); assert_eq!(debouncer.update(false), None); assert_eq!(debouncer.update(false), Some(Edge::Falling)); assert_eq!(debouncer.update(false), None); assert!(debouncer.is_low()); } #[test] fn test_debounce_16() { // Sixteen pressed updates required let mut debouncer: Debouncer<u16, Repeat16> = debounce_16(); assert!(debouncer.is_low()); for _ in 0..15 { assert_eq!(debouncer.update(true), None); assert!(!debouncer.is_high()); } assert_eq!(debouncer.update(true), Some(Edge::Rising)); assert!(debouncer.is_high()); assert_eq!(debouncer.update(true), None); assert!(debouncer.is_high()); } #[test] fn test_is_low_high() { // Initially low let mut debouncer: Debouncer<u8, Repeat8> = debounce_8(); assert!(debouncer.is_low()); assert!(!debouncer.is_high()); // Depressed updates don't change the situation debouncer.update(false); assert!(debouncer.is_low()); assert!(!debouncer.is_high()); // A pressed update causes neither low nor high state for _ in 0..7 { assert!(debouncer.update(true).is_none()); assert!(!debouncer.is_low()); assert!(!debouncer.is_high()); } // Once complete, the state is high assert_eq!(debouncer.update(true), Some(Edge::Rising)); assert!(!debouncer.is_low()); assert!(debouncer.is_high()); // Consecutive pressed updates don't trigger an edge but are still high assert!(debouncer.update(true).is_none()); assert!(!debouncer.is_low()); assert!(debouncer.is_high()); } /// Ensure the promised low RAM consumption. #[test] fn test_ram_consumption() { assert_eq!(std::mem::size_of_val(&debounce_2()), 1); assert_eq!(std::mem::size_of_val(&debounce_8()), 1); assert_eq!(std::mem::size_of_val(&debounce_9()), 2); assert_eq!(std::mem::size_of_val(&debounce_16()), 2); } }