update example comments

Author: strom-und-spiele

examples/adc.rs

@@ -19,7 +19,6 @@ fn main() -> ! {
     let clocks = rcc.cfgr.freeze(&mut dp.FLASH.constrain().acr);
 
     // set up adc1
-    #[rustfmt::skip]
     let mut adc1 = adc::Adc::adc1(
         dp.ADC1, // The ADC we are going to control
         // The following is only needed to make sure the clock signal for the ADC is set up
@@ -30,47 +29,34 @@ fn main() -> ! {
         clocks,
         // If everything is set up correctly, we'll get `Some(adc1)`. to access it, we need to `unwrap`
         // it. If there was an error, we'll get `None` and this unwrap will `panic!`.
-    ).unwrap();
+    )
+    .unwrap();
 
     // Set up pin PA0 as analog pin.
     // This pin is connected to the user button on the stm32f3discovery board.
     let mut gpio_a = dp.GPIOA.split(&mut rcc.ahb);
     let mut adc1_in1_pin = gpio_a.pa0.into_analog(&mut gpio_a.moder, &mut gpio_a.pupdr);
 
-    // Be aware that the values in the table below depend on the input of VREF
-    // Also know that and that the ADC hardware unit always rounds down.
-    //
+    // Be aware that the values in the table below depend on the input of VREF.
     // To have a stable VREF input, put a condensator and a volt limiting diode in front of it.
     //
-    // To compensate for the unit and integer math rounding down, use the following formula:
-    // ```rust
-    // // [setup as above]
-    // let mut adc: u3216 = adc1.read(&mut adc1_in1_pin).expect('Error reading adc1.');
-    // // add '0.5' to the adc value, compensating the ADC hardware rounding down
-    // adc <<= 1;
-    // adc += 1;
-    // // multiply it by '300 mV', converting to your voltage level
-    // let mut volt_mv = adc * 300;
-    // // make up for the coming integer division
-    // volt_mv += 1 << 12;
-    // // undo the first bitshift above and the 12bit ADC size
-    // volt_mv >>= 13;
-    // println!("Was reading {} mV", volt_mv);
-    // ```
+    // Also know that integer division and the ADC hardware unit always round down.
+    // To make up for those errors, see this forum entry:
+    // [https://forum.allaboutcircuits.com/threads/why-adc-1024-is-correct-and-adc-1023-is-just-plain-wrong.80018/]
     hprintln!("
     The ADC has a 12 bit resolution, i.e. if your reference Value is 3V:
         approx. ADC value | approx. volt value
         ==================+===================
-                        0 |       0 mV
-                     2048 |     150 mV
-                     4095 |     300 mV
+                        0 |        0 mV
+                     2048 |     1500 mV
+                     4095 |     3000 mV
 
     If you are using a STM32F3Discovery, PA0 is connected to the User Button.
     Pressing it should connect the user Button to to HIGH and the value should change from 0 to 4095.
     ").expect("Error using hprintln.");
 
     loop {
         let adc1_in1_data: u16 = adc1.read(&mut adc1_in1_pin).expect("Error reading adc1.");
-        hprintln!("PA0 reads {}", adc1_in1_data).unwrap_or(());
+        hprintln!("PA0 reads {}", adc1_in1_data).ok();
     }
 }