Make PWM example compile without feature

Author: TheZoq2

examples/pwm.rs

@@ -29,22 +29,22 @@ fn main() -> ! {
     let mut gpiob = p.GPIOB.split(&mut rcc.apb2);
 
     // TIM2
-    // let c1 = gpioa.pa0.into_alternate_push_pull(&mut gpioa.crl);
-    // let c2 = gpioa.pa1.into_alternate_push_pull(&mut gpioa.crl);
-    // let c3 = gpioa.pa2.into_alternate_push_pull(&mut gpioa.crl);
-    // let c4 = gpioa.pa3.into_alternate_push_pull(&mut gpioa.crl);
+    let c1 = gpioa.pa0.into_alternate_push_pull(&mut gpioa.crl);
+    let c2 = gpioa.pa1.into_alternate_push_pull(&mut gpioa.crl);
+    let c3 = gpioa.pa2.into_alternate_push_pull(&mut gpioa.crl);
+    let c4 = gpioa.pa3.into_alternate_push_pull(&mut gpioa.crl);
 
     // TIM3
     // let c1 = gpioa.pa6.into_alternate_push_pull(&mut gpioa.crl);
     // let c2 = gpioa.pa7.into_alternate_push_pull(&mut gpioa.crl);
     // let c3 = gpiob.pb0.into_alternate_push_pull(&mut gpiob.crl);
     // let c4 = gpiob.pb1.into_alternate_push_pull(&mut gpiob.crl);
 
-    // TIM4
-    let c1 = gpiob.pb6.into_alternate_push_pull(&mut gpiob.crl);
-    let c2 = gpiob.pb7.into_alternate_push_pull(&mut gpiob.crl);
-    let c3 = gpiob.pb8.into_alternate_push_pull(&mut gpiob.crh);
-    let c4 = gpiob.pb9.into_alternate_push_pull(&mut gpiob.crh);
+    // TIM4 (Only available with the "medium" density feature)
+    // let c1 = gpiob.pb6.into_alternate_push_pull(&mut gpiob.crl);
+    // let c2 = gpiob.pb7.into_alternate_push_pull(&mut gpiob.crl);
+    // let c3 = gpiob.pb8.into_alternate_push_pull(&mut gpiob.crh);
+    // let c4 = gpiob.pb9.into_alternate_push_pull(&mut gpiob.crh);
 
     let mut pwm = Timer::tim4(p.TIM4, &clocks, &mut rcc.apb1)
         .pwm((c1, c2, c3, c4), &mut afio.mapr, 1.khz())