From bcdb5e3c0ffbf401ee8747ff3887ca9ba00e177d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Robert=20J=C3=B6rdens?= <rj@quartiq.de>
Date: Mon, 10 May 2021 17:31:53 +0200
Subject: [PATCH] dsp/lowpass,lockin: const generics

---
 CHANGELOG.md         |  4 ++++
 Cargo.lock           |  1 -
 README.md            |  1 +
 dsp/Cargo.toml       |  1 -
 dsp/benches/micro.rs |  7 +++----
 dsp/src/lockin.rs    |  5 ++---
 dsp/src/lowpass.rs   | 16 ++++++++++------
 src/bin/lockin.rs    |  3 +--
 8 files changed, 21 insertions(+), 17 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 04aa2fe..70665b4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,8 +9,12 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Added
 
+* Telemetry
+
 ### Changed
 
+* Const generics bumping the MSRV to 1.51.0
+
 ### Fixed
 
 ## [v0.5.0] - 2021-04-21
diff --git a/Cargo.lock b/Cargo.lock
index 06309e3..b72b0be 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -215,7 +215,6 @@ name = "dsp"
 version = "0.1.0"
 dependencies = [
  "easybench",
- "generic-array 0.14.4",
  "libm",
  "miniconf",
  "ndarray",
diff --git a/README.md b/README.md
index 80cda1d..b6c1af7 100644
--- a/README.md
+++ b/README.md
@@ -37,6 +37,7 @@ to implement different use cases. Several applications are provides by default
 * Get [rustup](https://rustup.rs/)
 * `rustup target add thumbv7em-none-eabihf`
 * `cargo build --release`
+* Minimum supported Rust version (MSRV) is 1.51.0
 * When using debug (non `--release`) mode, increase the sample interval significantly.
   The added error checking code and missing optimizations may lead to the code
   missing deadlines and panicing.
diff --git a/dsp/Cargo.toml b/dsp/Cargo.toml
index 7b680d3..f9f680b 100644
--- a/dsp/Cargo.toml
+++ b/dsp/Cargo.toml
@@ -7,7 +7,6 @@ edition = "2018"
 [dependencies]
 libm = "0.2.1"
 serde = { version = "1.0", features = ["derive"], default-features = false }
-generic-array = "0.14"
 num = { version = "0.4.0", default-features = false }
 miniconf = "0.1"
 
diff --git a/dsp/benches/micro.rs b/dsp/benches/micro.rs
index 22a2540..c3588df 100644
--- a/dsp/benches/micro.rs
+++ b/dsp/benches/micro.rs
@@ -1,7 +1,6 @@
 use core::f32::consts::PI;
 
 use easybench::bench_env;
-use generic_array::typenum::U4;
 
 use dsp::{atan2, cossin, iir, iir_int, Lowpass, PLL, RPLL};
 
@@ -72,13 +71,13 @@ fn iir_bench() {
 }
 
 fn lowpass_bench() {
-    let mut dut = Lowpass::<U4>::default();
+    let mut dut = Lowpass::<4>::default();
     println!(
-        "Lowpass::<U4>::update(x, k): {}",
+        "Lowpass::<4>::update(x, k): {}",
         bench_env((0x32421, 14), |(x, k)| dut.update(*x, *k))
     );
     println!(
-        "Lowpass::<U4>::update(x, 14): {}",
+        "Lowpass::<4>::update(x, 14): {}",
         bench_env(0x32421, |x| dut.update(*x, 14))
     );
 }
diff --git a/dsp/src/lockin.rs b/dsp/src/lockin.rs
index 613a133..a9f5e84 100644
--- a/dsp/src/lockin.rs
+++ b/dsp/src/lockin.rs
@@ -1,12 +1,11 @@
 use super::{Complex, ComplexExt, Lowpass, MulScaled};
-use generic_array::ArrayLength;
 
 #[derive(Clone, Default)]
-pub struct Lockin<N: ArrayLength<i32>> {
+pub struct Lockin<const N: usize> {
     state: [Lowpass<N>; 2],
 }
 
-impl<N: ArrayLength<i32>> Lockin<N> {
+impl<const N: usize> Lockin<N> {
     /// Update the lockin with a sample taken at a given phase.
     pub fn update(&mut self, sample: i32, phase: i32, k: u8) -> Complex<i32> {
         // Get the LO signal for demodulation and mix the sample;
diff --git a/dsp/src/lowpass.rs b/dsp/src/lowpass.rs
index 10d5838..265929b 100644
--- a/dsp/src/lowpass.rs
+++ b/dsp/src/lowpass.rs
@@ -1,16 +1,20 @@
-use generic_array::{ArrayLength, GenericArray};
-
 /// Arbitrary order, high dynamic range, wide coefficient range,
 /// lowpass filter implementation. DC gain is 1.
 ///
 /// Type argument N is the filter order.
-#[derive(Clone, Default)]
-pub struct Lowpass<N: ArrayLength<i32>> {
+#[derive(Clone)]
+pub struct Lowpass<const N: usize> {
     // IIR state storage
-    y: GenericArray<i32, N>,
+    y: [i32; N],
 }
 
-impl<N: ArrayLength<i32>> Lowpass<N> {
+impl<const N: usize> Default for Lowpass<N> {
+    fn default() -> Self {
+        Lowpass { y: [0i32; N] }
+    }
+}
+
+impl<const N: usize> Lowpass<N> {
     /// Update the filter with a new sample.
     ///
     /// # Args
diff --git a/src/bin/lockin.rs b/src/bin/lockin.rs
index 944b87a..a187767 100644
--- a/src/bin/lockin.rs
+++ b/src/bin/lockin.rs
@@ -3,7 +3,6 @@
 #![no_main]
 
 use embedded_hal::digital::v2::InputPin;
-use generic_array::typenum::U4;
 
 use serde::Deserialize;
 
@@ -92,7 +91,7 @@ const APP: () = {
 
         timestamper: InputStamper,
         pll: RPLL,
-        lockin: Lockin<U4>,
+        lockin: Lockin<4>,
     }
 
     #[init(spawn=[settings_update, telemetry])]