add comments to project rs

code/project/src/main.rs

@@ -16,6 +16,7 @@ use microbit::{
         gpio::{p0::P0_05, Floating, Input},
         saadc::SaadcConfig,
         timer::Timer,
+        timer::Timer,
         Saadc,
     },
     pac::TIMER1,
@@ -27,9 +28,8 @@ use ordered_float::NotNan;
 use panic_rtt_target as _;
 use rtt_target::{rprintln, rtt_init_print};
 
-// Microbit-spectrum
+// Microbit-spectrum ported constants
 const FFT_WIDTH: usize = 64;
-/// ADC is signed; it is configured for a sample precision of 10 bits. Must match below.
 const ADC_MAX: usize = 512;
 
 const NOTES: [&str; 12] = [
@@ -96,6 +96,7 @@ const NOTE_IMAGE_BITMAPS: [[[u8; 5]; 5]; 7] = [
     ],
 ];
 
+// Read FFT-WIDTH numer of samples from the saadc channel. Collect these sequentially and return the array
 fn read_samples(saadc: &mut Saadc, mic_in: &mut P0_05<Input<Floating>>) -> [i16; FFT_WIDTH] {
     let mut result = [0; FFT_WIDTH];
     for r in &mut result {
@@ -104,7 +105,7 @@ fn read_samples(saadc: &mut Saadc, mic_in: &mut P0_05<Input<Floating>>) -> [i16;
     result
 }
 
-// Microbit-spectrum - read function
+// Adapted from Microbit-spectrum - `fn spectrum`
 fn samples_to_freq(
     samples: [i16; FFT_WIDTH],
     window: [f32; FFT_WIDTH],
@@ -133,11 +134,15 @@ fn samples_to_freq(
     *freqs
 }
 
+// When complete, getting the dominant frequency should be about as follows:
+// 1) window the data in a sensible way
+// 2) Take an FFT of the window
+// 3) Identify the fft frequency with the largest magnitude in the window and return it
 fn get_dominant_freq(_freqs: [Complex<f32>; FFT_WIDTH / 2]) -> f32 {
-    // todo!();
     0.0
 }
 
+// Simple frequencry to rounded note/octave value
 fn get_note(freq: f32) -> (usize, f32) {
     if freq > 0.0 {
         let note_num = log2f(freq / 440.0) * 12.0;
@@ -148,6 +153,7 @@ fn get_note(freq: f32) -> (usize, f32) {
     (0, 0.0)
 }
 
+// Return the pre-defined base image, which matches the offset of the node
 fn get_image(noctive: (usize, f32)) -> [[u8; 5]; 5] {
     let (note, _octive) = noctive; // TODO - Add octive and flat modifier to display
     if note > 0 {
@@ -171,7 +177,7 @@ fn init() -> ! {
 
     let _ = mic_run.set_high();
 
-    let saadc_config: SaadcConfig = SaadcConfig::default();
+    let saadc_config: SaadcConfig = SaadcConfig::default(); // Testing may show that more explicit Saadc configuration is needed
     let mut saadc: Saadc = Saadc::new(board.ADC, saadc_config);
 
 
@@ -186,10 +192,10 @@ fn init() -> ! {
         let samples: [i16; FFT_WIDTH] = read_samples(&mut saadc, &mut mic_in);
         let freqs: [Complex<f32>; FFT_WIDTH / 2] = samples_to_freq(samples, window);
         let dominant_freq: f32 = get_dominant_freq(freqs);
-        let noctive: (usize, f32) = get_note(dominant_freq); //note + octive tuple
+        let noctive: (usize, f32) = get_note(dominant_freq); //noctive = note + octive tuple
         let bitmap: [[u8; 5]; 5] = get_image(noctive);
         DISPLAY.with_lock(|display: &mut Display<TIMER1>| {
-            display.show(&BitImage::new(&bitmap)); // XXX Not the most memory efficient - Improve
+            display.show(&BitImage::new(&bitmap)); // A better place can be found for the new constructor
         });
         rprintln!("{}", NOTES[noctive.0]);
         timer.delay(400);