diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0a42efa..04aa2fe 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,73 @@
-# Changelog
+# Change Log
 
-## [v0.2.0] 2019-05-28
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](http://keepachangelog.com/)
+and this project adheres to [Semantic Versioning](http://semver.org/).
+
+## [Unreleased]
+
+### Added
+
+### Changed
+
+### Fixed
+
+## [v0.5.0] - 2021-04-21
+
+### Added
+
+* Batch sample processing
+* DMA for ADC and DAC batches
+* Pounder profile streaming
+* DSP library with lots of optimized algorithms
+* Digital input support
+* Hardware in the loop continuous integration testing
+* Dependency updates
+* MQTT settings interface through miniconf/minimq
+* Multi-binary support
+* DHCP support
+
+### Changed
+
+* Removed JSON-over-TCP interface
+
+### Fixed
+
+* Robust EEPROM MAC address reading slow supply start
+
+## [v0.4.1] - 2020-06-23
+
+### Fixed
+
+* Fix DAC clr/ldac, SPI speed
+
+## [v0.4.0] - 2020-06-22
+
+### Added
+
+* Hardware v1.1 only
+* AD9959/Pounder support
+
+### Changed
+
+* HAL port
+
+## [v0.3.0] - 2020-01-20
+
+### Added
+
+* Red LED handling
+* EEPROM MAC address reading
+
+### Changed
+
+* Panic handler cleanup
+* Dependency updates (smoltcp, rtfm)
+
+## [v0.2.0] - 2019-05-28
+
+### Added
 
 * Initial basic release
 * Ethernet support
@@ -9,6 +76,15 @@
 * ADC/DAC timing and interrupts
 * Board configuration, bootstrap
 
-## [v0.1.0] 2019-03-10
+## [v0.1.0] - 2019-03-10
+
+### Added
 
 * First bits of code published
+
+[Unreleased]: https://github.com/quartiq/stabilizer/compare/v0.5.0...HEAD
+[v0.5.0]: https://github.com/quartiq/stabilizer/compare/v0.4.1...v0.5.0
+[v0.4.1]: https://github.com/quartiq/stabilizer/compare/v0.4.0...v0.4.1
+[v0.4.0]: https://github.com/quartiq/stabilizer/compare/v0.3.0...v0.4.0
+[v0.3.0]: https://github.com/quartiq/stabilizer/compare/v0.2.0...v0.3.0
+[v0.2.0]: https://github.com/quartiq/stabilizer/compare/v0.1.0...v0.2.0
diff --git a/Cargo.lock b/Cargo.lock
index 9007083..a002739 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -732,7 +732,7 @@ dependencies = [
 
 [[package]]
 name = "stabilizer"
-version = "0.4.1"
+version = "0.5.0"
 dependencies = [
  "ad9959",
  "asm-delay",
diff --git a/Cargo.toml b/Cargo.toml
index 29480d5..095fb74 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "stabilizer"
-version = "0.4.1"
+version = "0.5.0"
 authors = ["Robert Jördens <rj@quartiq.de>"]
 description = "Firmware for the Sinara Stabilizer board (stm32h743, eth, poe, 2 adc, 2 dac)"
 categories = ["embedded", "no-std", "hardware-support", "science"]
diff --git a/src/bin/dual-iir.rs b/src/bin/dual-iir.rs
index b275de0..65d3f2e 100644
--- a/src/bin/dual-iir.rs
+++ b/src/bin/dual-iir.rs
@@ -31,9 +31,17 @@ pub struct Settings {
 impl Default for Settings {
     fn default() -> Self {
         Self {
+            // Analog frontend programmable gain amplifier gains (G1, G2, G5, G10)
             afe: [AfeGain::G1, AfeGain::G1],
+            // IIR filter tap gains are an array `[b0, b1, b2, a1, a2]` such that the
+            // new output is computed as `y0 = a1*y1 + a2*y2 + b0*x0 + b1*x1 + b2*x2`.
+            // The array is `iir_state[channel-index][cascade-index][coeff-index]`.
+            // The IIR coefficients can be mapped to other transfer function
+            // representations, for example as described in https://arxiv.org/abs/1508.06319
             iir_ch: [[iir::IIR::new(1., -SCALE, SCALE); IIR_CASCADE_LENGTH]; 2],
+            // Permit the DI1 digital input to suppress filter output updates.
             allow_hold: false,
+            // Force suppress filter output updates.
             force_hold: false,
         }
     }
@@ -48,7 +56,6 @@ const APP: () = {
         dacs: (Dac0Output, Dac1Output),
         mqtt: MqttInterface<Settings>,
 
-        // Format: iir_state[ch][cascade-no][coeff]
         #[init([[[0.; 5]; IIR_CASCADE_LENGTH]; 2])]
         iir_state: [[iir::Vec5; IIR_CASCADE_LENGTH]; 2],
         settings: Settings,