From d0216915c2a308874ff15e42b37407e84e3e8e06 Mon Sep 17 00:00:00 2001
From: Paul van Tilburg <paul@luon.net>
Date: Wed, 6 Mar 2019 21:16:05 +0100
Subject: [PATCH] Add an interrupt to the user button; reverse LED cycle
 direction

---
 src/main.rs | 44 ++++++++++++++++++++++++++++++++++++--------
 1 file changed, 36 insertions(+), 8 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index 3aed1ce..4aeaec4 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -6,7 +6,7 @@
 extern crate panic_semihosting;
 
 //use cortex_m_semihosting::hprintln;
-use hal::gpio::{ExtiPin, Output, PushPull};
+use hal::gpio::{Edge, ExtiPin, Floating, Input, Output, PushPull};
 use hal::prelude::*;
 use rtfm::app;
 
@@ -14,10 +14,18 @@ type Led = hal::gpio::gpiod::PD<Output<PushPull>>;
 
 const PERIOD: u32 = 8_000_000;
 
+pub enum LedDirection {
+    Clockwise,
+    CounterClockwise,
+}
+
 #[app(device = hal::stm32)]
 const APP: () = {
-    static mut index: usize = ();
+    static mut button: hal::gpio::gpioa::PA0<Input<Floating>> = ();
     static mut leds: [Led; 4] = ();
+    static mut led_cycle_direction: LedDirection = LedDirection::Clockwise;
+    static mut led_index: usize = 0;
+    static mut exti: hal::stm32::EXTI = ();
 
     #[init(spawn = [switch_leds])]
     fn init() -> init::LateResources {
@@ -31,21 +39,41 @@ const APP: () = {
         ];
         spawn.switch_leds().unwrap();
 
+        // Set up the EXTI0 interrup for the user button.
+        let mut exti = device.EXTI;
+        let gpioa = device.GPIOA.split();
+        let mut button = gpioa.pa0.into_floating_input();
+        button.enable_interrupt(&mut exti);
+        button.trigger_on_edge(&mut exti, Edge::RISING);
 
-        init::LateResources { index: 0, leds }
+        init::LateResources { button, exti, leds }
     }
 
-    #[task(schedule = [switch_leds], resources = [index, leds])]
+    #[task(schedule = [switch_leds],
+        resources = [led_index, led_cycle_direction, leds])]
     fn switch_leds() {
-        let index = *resources.index;
+        let led_index = *resources.led_index;
         let num_leds = resources.leds.len();
-        resources.leds[index].set_high();
-        resources.leds[(index + 2) % num_leds].set_low();
-        *resources.index = (index + 1) % 4;
+
+        resources.leds[led_index].set_high();
+        resources.leds[(led_index + 2) % num_leds].set_low();
+        *resources.led_index = match *resources.led_cycle_direction {
+            LedDirection::Clockwise => (led_index + 1) % num_leds,
+            LedDirection::CounterClockwise => (led_index + 3) % num_leds,
+        };
 
         schedule.switch_leds(scheduled + PERIOD.cycles()).unwrap();
     }
 
+    #[interrupt(binds = EXTI0, resources = [button, exti, led_cycle_direction])]
+    fn button_pressed() {
+        *resources.led_cycle_direction = match *resources.led_cycle_direction {
+            LedDirection::Clockwise => LedDirection::CounterClockwise,
+            LedDirection::CounterClockwise => LedDirection::Clockwise,
+        };
+        resources.button.clear_interrupt_pending_bit(resources.exti);
+    }
+
     extern "C" {
         fn UART4();
     }