Merge pull request #832 from quartiq/iir-rework

iir rework
quartiq · Jan 15, 2024 · f8db161 · f8db161
2 parents ededc69 + b1acca2
commit f8db161
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Showing 6 changed files with 28 additions and 18 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -18,6 +18,8 @@ console.
 ### Changed
 * Broker is no longer configured at compile time, but is maintained in device memory
 * MSRV bumped to v1.66
+* The IIR (biquad) filter used for PID action has changed its serialization format.
+  See also the `iir_coefficients` Python CLI implementation.
 
 ## [0.9.0](https://github.com/quartiq/stabilizer/compare/v0.8.1...v0.9.0)
 
@@ -35,7 +37,7 @@ console.
  * `hitl/streaming.py` no longer requires a prefix
  * Streaming now supports UDP multicast addresses
 
-## [v0.8.1](https://github.com/quartiq/stabilizer/compare/v0.8.0...v0.8.1) - 2022-11-14)
+## [v0.8.1](https://github.com/quartiq/stabilizer/compare/v0.8.0...v0.8.1) - 2022-11-14
 
 * Fixed the python package dependencies
 

diff --git a/Cargo.lock b/Cargo.lock
diff --git a/Cargo.toml b/Cargo.toml
@@ -50,7 +50,7 @@ cortex-m-rtic = "1.0"
 embedded-hal = "0.2.7"
 num_enum = { version = "0.7.2", default-features = false }
 paste = "1"
-idsp = "0.13"
+idsp = "0.14.1"
 ad9959 = { path = "ad9959", version = "0.2.1" }
 serial-settings = {path = "serial-settings"}
 mcp230xx = "1.0"

diff --git a/hitl/loopback.py b/hitl/loopback.py
@@ -27,10 +27,10 @@ def static_iir_output(output_voltage):
     """
     machine_units = voltage_to_machine_units(output_voltage)
     return {
-        'y_min': machine_units,
-        'y_max': machine_units,
-        'y_offset': 0,
         'ba': [1, 0, 0, 0, 0],
+        'u': 0,
+        'min': machine_units,
+        'max': machine_units,
     }
 
 

diff --git a/py/stabilizer/iir_coefficients.py b/py/stabilizer/iir_coefficients.py
@@ -300,10 +300,10 @@ async def configure():
         # Note: In the future, we will need to Handle higher-order cascades.
         await interface.set(f"/iir_ch/{args.channel}/0", {
             "ba": coefficients,
-            "y_min": stabilizer.voltage_to_machine_units(args.y_min),
-            "y_max": stabilizer.voltage_to_machine_units(args.y_max),
-            "y_offset": stabilizer.voltage_to_machine_units(
-                args.y_offset + forward_gain * args.x_offset)
+            "u": stabilizer.voltage_to_machine_units(
+                args.y_offset + forward_gain * args.x_offset),
+            "min": stabilizer.voltage_to_machine_units(args.y_min),
+            "max": stabilizer.voltage_to_machine_units(args.y_max),
         })
 
     asyncio.run(configure())

diff --git a/src/bin/dual-iir.rs b/src/bin/dual-iir.rs
@@ -94,10 +94,9 @@ pub struct Settings {
     /// * `<n>` specifies which channel to configure. `<n>` := [0, 1]
     /// * `<m>` specifies which cascade to configure. `<m>` := [0, 1], depending on [IIR_CASCADE_LENGTH]
     ///
-    /// # Value
-    /// See [iir::IIR#miniconf]
+    /// See [iir::Biquad]
     #[tree(depth(2))]
-    iir_ch: [[iir::IIR<f32>; IIR_CASCADE_LENGTH]; 2],
+    iir_ch: [[iir::Biquad<f32>; IIR_CASCADE_LENGTH]; 2],
 
     /// Specified true if DI1 should be used as a "hold" input.
     ///
@@ -150,6 +149,9 @@ pub struct Settings {
 
 impl Default for Settings {
     fn default() -> Self {
+        let mut i = iir::Biquad::IDENTITY;
+        i.set_min(-SCALE);
+        i.set_max(SCALE);
         Self {
             // Analog frontend programmable gain amplifier gains (G1, G2, G5, G10)
             afe: [Gain::G1, Gain::G1],
@@ -158,7 +160,7 @@ impl Default for Settings {
             // 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],
+            iir_ch: [[i; IIR_CASCADE_LENGTH]; 2],
 
             // Permit the DI1 digital input to suppress filter output updates.
             allow_hold: false,
@@ -199,7 +201,7 @@ mod app {
         afes: (AFE0, AFE1),
         adcs: (Adc0Input, Adc1Input),
         dacs: (Dac0Output, Dac1Output),
-        iir_state: [[iir::Vec5<f32>; IIR_CASCADE_LENGTH]; 2],
+        iir_state: [[[f32; 4]; IIR_CASCADE_LENGTH]; 2],
         generator: FrameGenerator,
         cpu_temp_sensor: stabilizer::hardware::cpu_temp_sensor::CpuTempSensor,
     }
@@ -258,7 +260,7 @@ mod app {
             afes: stabilizer.afes,
             adcs: stabilizer.adcs,
             dacs: stabilizer.dacs,
-            iir_state: [[[0.; 5]; IIR_CASCADE_LENGTH]; 2],
+            iir_state: [[[0.; 4]; IIR_CASCADE_LENGTH]; 2],
             generator,
             cpu_temp_sensor: stabilizer.temperature_sensor,
         };
@@ -345,7 +347,13 @@ mod app {
                                     .iter()
                                     .zip(iir_state[channel].iter_mut())
                                     .fold(x, |yi, (ch, state)| {
-                                        ch.update(state, yi, hold)
+                                        let filter = if hold {
+                                            &iir::Biquad::HOLD
+                                        } else {
+                                            ch
+                                        };
+
+                                        filter.update(state, yi)
                                     });
 
                                 // Note(unsafe): The filter limits must ensure that the value is in range.