move config docs to config

src/lowpass.rs

@@ -7,28 +7,30 @@ use crate::Filter;
 ///
 /// The filter will cleanly saturate towards the `i32` range.
 ///
-/// The filter configuration `Config` contains its gains.
-///
-/// For the first-order lowpass this the corner frequency in scaled Q31:
-/// `k = pi*(1 << 31)*f0/fn` where
-/// `f0` is the 3dB corner frequency and
-/// `fn` is the Nyquist frequency.
-/// The corner frequency is warped in the usual way.
-///
-/// For the second-order lowpass this is `[k**2/(1 << 32), -k/q]` with `q = 1/sqrt(2)`
-/// for a Butterworth response.
-/// In addition to the poles at the corner frequency The filters have zeros at Nyquist.
-///
-/// The first-order lowpass works fine and accurate for any positive gain
-/// `1 <= k <= (1 << 31) - 1`.
-/// The second-order lowpass works and is accurate for
-/// `1 << 16 <= k <= q*(1 << 31)`.
 ///
 /// Both filters have been optimized for accuracy, dynamic range, and
 /// speed on Cortex-M7.
 #[derive(Copy, Clone)]
 pub struct Lowpass<const N: usize>(pub(crate) [i64; N]);
 impl<const N: usize> Filter for Lowpass<N> {
+    /// The filter configuration `Config` contains the filter gains.
+    ///
+    /// For the first-order lowpass this is a single element array `[k]` with
+    /// the corner frequency in scaled Q31:
+    /// `k = pi*(1 << 31)*f0/fn` where
+    /// `f0` is the 3dB corner frequency and
+    /// `fn` is the Nyquist frequency.
+    /// The corner frequency is warped in the usual way.
+    ///
+    /// For the second-order lowpass this is `[k**2/(1 << 32), -k/q]` with `q = 1/sqrt(2)`
+    /// for a Butterworth response.
+    ///
+    /// In addition to the poles at the corner frequency the filters have zeros at Nyquist.
+    ///
+    /// The first-order lowpass works fine and accurate for any positive gain
+    /// `1 <= k <= (1 << 31) - 1`.
+    /// The second-order lowpass works and is accurate for
+    /// `1 << 16 <= k <= q*(1 << 31)`.
     type Config = [i32; N];
     fn update(&mut self, x: i32, k: &Self::Config) -> i32 {
         let mut d = x.saturating_sub((self.0[0] >> 32) as i32) as i64 * k[0] as i64;