fir init

src/agc.rs

@@ -0,0 +1,83 @@
+use num_complex::Complex;
+
+use crate::iq_reader::IqChunk;
+
+// Automatic Gain Control
+pub struct Agc {
+    // Previous power estimate
+    pub power_estimate: f32,
+    // Previous gain
+    pub current_gain: f32,
+    pub target_power: f32,
+    pub alpha_attack: f32,
+    pub alpha_release: f32,
+    pub beta: f32,
+    pub min_gain: f32,
+    pub max_gain: f32,
+}
+
+impl Agc {
+    pub fn new(sample_rate: f32, target_power: f32, min_gain: f32, max_gain: f32) -> Self {
+        // Target attack time 5 ms
+        let tau_attack = 0.005;
+
+        // Target release time 50 ms
+        let tau_release = 0.05;
+
+        let alpha_attack = 1.0 - f32::exp(-1.0 / (sample_rate * tau_attack));
+        let alpha_release = 1.0 - f32::exp(-1.0 / (sample_rate * tau_release));
+
+        let beta = 0.999;
+
+        let power_estimate = 0.0;
+        let current_gain = 1.0;
+
+        Self {
+            power_estimate,
+            current_gain,
+            target_power,
+            alpha_attack,
+            alpha_release,
+            beta,
+            min_gain,
+            max_gain,
+        }
+    }
+
+    pub fn process_chunk(&mut self, chunk: &mut IqChunk) {
+        for z in chunk.samples.iter_mut() {
+            let i = z.re;
+            let q = z.im;
+
+            // Instant Power
+            let inst_power = i * i + q * q;
+
+            let alpha = if inst_power > self.power_estimate {
+                self.alpha_attack
+            } else {
+                self.alpha_release
+            };
+
+            // IIR filter
+            let power_estimate = alpha * inst_power + (1.0 - alpha) * self.power_estimate;
+
+            // Update Power
+            self.power_estimate = power_estimate.max(1e-10);
+
+            let raw_gain = (self.target_power / self.power_estimate).sqrt();
+
+            // Gain in [min_gain ; max_gain]
+            let raw_gain = match raw_gain {
+                g if g < self.min_gain => self.min_gain,
+                g if g > self.max_gain => self.max_gain,
+                _ => raw_gain,
+            };
+
+            let final_gain = self.beta * self.current_gain + (1.0 - self.beta) * raw_gain;
+
+            self.current_gain = final_gain;
+
+            *z = Complex::new(i * final_gain, q * final_gain);
+        }
+    }
+}

src/fir.rs

@@ -0,0 +1,27 @@
+// Finite Impulse response + Decimation
+use crate::utils::ring_buffer::RingBuffer;
+use num_complex::Complex32;
+
+pub struct Fir<const N: usize> {
+    // Filter coefs
+    pub taps: [f32; N],
+
+    // Ring Buffer of samples
+    pub history: RingBuffer<Complex32>,
+
+    decimation_factor: usize,
+
+    // When to keep a sample
+    decimator_counter: usize,
+}
+
+impl<const N: usize> Fir<N> {
+    fn new(taps: [f32; N], decimation_factor: usize) -> Self {
+        Self {
+            taps,
+            history: RingBuffer::new(N),
+            decimation_factor,
+            decimator_counter: 0,
+        }
+    }
+}

src/iq_reader.rs

@@ -1,12 +1,12 @@
 use num_complex::Complex;
 use std::error::Error;
 use std::fs::File;
-use std::io::{BufRead, BufReader, Read};
-use std::os::unix::process::CommandExt;
+use std::io::{BufReader, ErrorKind, Read};
 
 pub type IqSample = Complex<f32>;
 
 // Data chunk
+#[derive(Debug)]
 pub struct IqChunk {
     pub samples: Vec<IqSample>,
 }
@@ -21,8 +21,8 @@ pub struct FileSource {
 }
 
 impl FileSource {
-    pub fn new(file_path: &str, chunk_samples_size: usize) -> Self {
-        let file = File::open(file_path).unwrap();
+    pub fn new(file_path: &str, chunk_samples_size: usize) -> Result<Self, Box<dyn Error>> {
+        let file = File::open(file_path)?;
 
         // Init buffer with size 16 Mo
         let reader = BufReader::with_capacity(16 * 1024 * 1024, file);
@@ -30,27 +30,44 @@ impl FileSource {
         // 1 sample = 2 bytes (1 byte : I, 1 byte : Q)
         let raw_reader = vec![0; chunk_samples_size * 2];
 
-        Self {
+        Ok(Self {
             reader,
             raw_buffer: raw_reader,
             chunk_samples_size,
-        }
+        })
     }
+}
 
-    pub fn read_chunk(&mut self) -> Option<IqChunk> {
-        // TODO : match for EOF
-        self.reader.read_exact(&mut self.raw_buffer);
+impl Iterator for FileSource {
+    type Item = Result<IqChunk, Box<dyn Error>>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        // Buffer read
+        match self.reader.read_exact(&mut self.raw_buffer) {
+            Ok(_) => {}
+
+            // EOF
+            Err(e) if e.kind() == ErrorKind::UnexpectedEof => {
+                return None;
+            }
+
+            Err(e) => {
+                return Some(Err(e.into()));
+            }
+        }
 
         // Output samples
         let mut samples = Vec::with_capacity(self.chunk_samples_size);
 
         // Buffer read
         for iq in self.raw_buffer.chunks(2) {
-            let i = (iq[0] as f32) / 128.0;
-            let q = (iq[1] as f32) / 128.0;
-            samples.push(Complex::new(i, q));
+            let i = iq[0] as i8;
+            let q = iq[1] as i8;
+            let i_f32 = (i as f32) / 128.0;
+            let q_f32 = (q as f32) / 128.0;
+            samples.push(Complex::new(i_f32, q_f32));
         }
 
-        Some(IqChunk { samples })
+        Some(Ok(IqChunk { samples }))
     }
 }

src/main.rs

@@ -1,5 +1,27 @@
-mod iq_reader;
+use crate::agc::Agc;
+use crate::iq_reader::FileSource;
+use std::error::Error;
 
-fn main() {
-    println!("Hello, world!");
+mod agc;
+mod fir;
+mod iq_reader;
+mod utils;
+
+fn main() -> Result<(), Box<dyn Error>> {
+    let source = FileSource::new("test.iq", 32769)?;
+
+    // for chunk in source {
+    //     println!("{chunk :?}");
+    // }
+
+    // 20 MSps
+    let mut agc = Agc::new(20_000_000.0, 0.1, 0.001, 100.0);
+
+    // Apply Auto Gain Control
+    for chunk_r in source {
+        let mut chunk = chunk_r?;
+        agc.process_chunk(&mut chunk);
+    }
+
+    Ok(())
 }

src/utils/mod.rs

@@ -0,0 +1 @@
+pub mod ring_buffer;

src/utils/ring_buffer.rs

@@ -0,0 +1,78 @@
+pub struct RingBuffer<T: Copy + Default> {
+    pub data: Vec<T>,
+
+    // Index to next writing element
+    pub head: usize,
+
+    // Actual size
+    pub size: usize,
+
+    pub capacity: usize,
+}
+
+impl<T: Copy + Default> RingBuffer<T> {
+    pub fn new(capacity: usize) -> Self {
+        assert!(capacity != 0);
+        Self {
+            data: vec![T::default(); capacity],
+            head: 0,
+            size: 0,
+            capacity,
+        }
+    }
+
+    pub fn write(&mut self, value: T) {
+        self.data[self.head] = value;
+        self.head = (self.head + 1) % self.capacity;
+        self.size = (self.size + 1).min(self.capacity);
+    }
+
+    pub fn read(&mut self) -> Option<T> {
+        if self.size == 0 {
+            return None;
+        }
+        let tail = (self.head + self.capacity - self.size) % self.capacity;
+        self.size -= 1;
+        Some(self.data[tail])
+    }
+
+    pub fn peek(&self) -> Option<&T> {
+        if self.size == 0 {
+            return None;
+        }
+        let last = (self.head + self.capacity - 1) % self.capacity;
+        Some(&self.data[last])
+    }
+
+    // Read N samples before
+    pub fn read_at(&self, delay: usize) -> Option<&T> {
+        if delay >= self.size {
+            return None;
+        }
+        let index = (self.head + self.capacity - 1 - delay) % self.capacity;
+        Some(&self.data[index])
+    }
+
+    pub fn write_read(&mut self, value: T, delay: usize) -> Option<T> {
+        let delayed = self.read_at(delay).copied();
+        self.write(value);
+        delayed
+    }
+
+    pub fn len(&self) -> usize {
+        self.size
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.size == 0
+    }
+
+    pub fn is_full(&self) -> bool {
+        self.size == self.capacity
+    }
+
+    pub fn clear(&mut self) {
+        self.head = 0;
+        self.size = 0;
+    }
+}