Video pwm (#2)

* creating video version

* cleanup

control-dc-motor/src/main.rs

@@ -1,67 +1,56 @@
 use gpio_cdev::{Chip, LineRequestFlags};
 
-const GPIO17: u32 = 17;
-const GPIO18: u32 = 18;
-
-// PWM Min duty cycle in ms
-const PWM_FREQUENCY_HZ: f64 = 100.0;
+const GPIO5: u32 = 5;
+const GPIO6: u32 = 6;
 
 enum Direction {
     Left,
     Right,
 }
 
+/**
+ * This program will turn a motor left and right every 5 seconds.
+ */
 fn main() -> Result<(), gpio_cdev::Error> {
-    // Open the GPIO chip; usually, it's gpiochip0 for the main GPIO controller on a Raspberry Pi
+    // 1. Open the GPIO chip; it's gpiochip0 for the main GPIO controller on a Raspberry Pi
     let mut chip = Chip::new("/dev/gpiochip0")?;
-    let mut current_direction = Direction::Left;
-    let mut last_direction_change = std::time::Instant::now();
-    let line17 = chip.get_line(GPIO17)?;
-    let line18 = chip.get_line(GPIO18)?;
-
+    let line5 = chip.get_line(GPIO5)?;
+    let line6 = chip.get_line(GPIO6)?;
     // Initially both are off
-    let line17 = line17.request(LineRequestFlags::OUTPUT, 0, "pwm")?;
-    let line18 = line18.request(LineRequestFlags::OUTPUT, 0, "pwm")?;
+    let line5 = line5.request(LineRequestFlags::OUTPUT, 0, "pwm")?;
+    let line6 = line6.request(LineRequestFlags::OUTPUT, 0, "pwm")?;
 
-    let duty_cycle = 99.0;
-    let time_on_ms = (duty_cycle / 100.0) * (1.0 / PWM_FREQUENCY_HZ) * 1000.0;
-    let time_off_ms = ((100.0 - duty_cycle) / 100.0) * (1.0 / PWM_FREQUENCY_HZ) * 1000.0;
+    // 2. Initially the motor is turning left
+    let mut current_direction = Direction::Left;
 
-    println!("Time on: {} ms, Time off: {} ms", time_on_ms, time_off_ms);
+    // 3. Keep track of the last time we changed direction
+    let mut last_direction_change = std::time::Instant::now();
 
     loop {
-        // Set the PWM frequency
-        // turn it on
+        // transform direction to GPIO signals
         match current_direction {
             Direction::Left => {
-                line17.set_value(1)?;
-                line18.set_value(0)?;
+                line5.set_value(1)?;
+                line6.set_value(0)?;
             }
             Direction::Right => {
-                line17.set_value(0)?;
-                line18.set_value(1)?;
+                line5.set_value(0)?;
+                line6.set_value(1)?;
             }
         }
-        std::thread::sleep(std::time::Duration::from_millis(time_on_ms as u64));
-        // turn it off
-        line17.set_value(0)?;
-        line18.set_value(0)?;
-        std::thread::sleep(std::time::Duration::from_millis(time_off_ms as u64));
-        // change direction
+
         if last_direction_change.elapsed().as_secs() >= 5 {
-            match current_direction {
-                Direction::Left => {
-                    current_direction = Direction::Right;
-                }
-                Direction::Right => {
-                    current_direction = Direction::Left;
-                }
-            }
+            // Turn off the motor
+            line5.set_value(0)?;
+            line6.set_value(0)?;
+
+            // Change direction
+            current_direction = match current_direction {
+                Direction::Left => Direction::Right,
+                Direction::Right => Direction::Left
+            };
             last_direction_change = std::time::Instant::now();
-            // let the motor stop for a while
             std::thread::sleep(std::time::Duration::from_secs(1));
         }
     }
-
-    Ok(())
 }