dimming

src/display.rs

@@ -97,6 +97,10 @@ impl Brightness {
         self.0
     }
 
+    pub fn dimm(self, scale: u8) -> Brightness {
+        Brightness(self.0 >> scale)
+    }
+
     // Scales brightness (0-255) to range between IO_SEGMENT_ON_MIN_US and IO_SEGMENT_ON_MAX_US
     pub fn scale_brightness(self) -> u32 {
         // Using >> to avoid 32bit division which take ~576 cycles

src/main.rs

@@ -50,6 +50,11 @@ pub const IO_SEGMENT_RATE_US: u32 = 1000; // Time in μs between segment updates
 pub const IO_SEGMENT_ON_MIN_US: u32 = 80; // How long in μs to hold segment LEDs on (dark)
 pub const IO_SEGMENT_ON_MAX_US: u32 = 700; // How long in μs to hold segment LEDs on (bright)
 
+// Dimming
+pub const DISPLAY_FPS: u16 = (1_000_000 / (IO_SEGMENT_RATE_US * DISPLAY_SEGMENTS as u32)) as u16;
+pub const DISPLAY_DIMM_FRAMES: u16 = DISPLAY_FPS * 10; // How many frames of inactivity before dimming
+pub const DISPLAY_DIMM_SCALE: u8 = 4; // Number of bit shifts of brighness to dim
+
 // Calculator setup
 pub const STACK_DEPTH: usize = 7;
 type Calc = StackCalc<f32, STACK_DEPTH, 5, u8>;
@@ -115,6 +120,7 @@ pub struct IOLoop {
     keyboard: Keyboard,
     readount: Option<KeyReadout>,
     debounce: Debounce,
+    sleep_timer: u16,
 }
 
 impl IOLoop {
@@ -128,6 +134,7 @@ impl IOLoop {
             keyboard,
             readount: None,
             debounce: Default::default(),
+            sleep_timer: 0,
         }
     }
 
@@ -151,19 +158,36 @@ impl IOLoop {
             // Start from first segment
             self.index = 0;
 
-            // Full keyboard scan complete, debounce and return result
-            self.debounce.input(self.readount.take())
+            // Full keyboard scan complete, debounce
+            let key = self.debounce.input(self.readount.take());
+
+            // Reset or advance sleep timer
+            if key.is_some() {
+                self.sleep_timer = 0;
+            } else {
+                self.sleep_timer = self.sleep_timer.saturating_add(1);
+            }
+
+            key
         } else {
             None
         }
     }
 
+    pub fn is_sleep(&self) -> bool {
+        self.sleep_timer >= DISPLAY_DIMM_FRAMES
+    }
+
     pub fn display_on(&mut self) -> Brightness {
         self.select_off();
         let segment = self.dispaly[self.index];
         let brighness = segment.apply(&mut self.segment_pins);
         self.select_on();
-        brighness
+        if self.is_sleep() {
+            brighness.dimm(DISPLAY_DIMM_SCALE)
+        } else {
+            brighness
+        }
     }
 
     pub fn display_off(&mut self) {