Updates

* Make next_state() private
* Added Gain enum and doc comments
* Changed Function args to use Gain enum rather than u8

Author: boondocklabs

examples/fmac.rs

@@ -3,7 +3,6 @@
 #![no_main]
 #![no_std]
 
-use cortex_m::asm::wfi;
 use hal::prelude::*;
 use hal::stm32;
 use stm32g4xx_hal as hal;
@@ -17,7 +16,7 @@ use utils::logger::info;
 
 use stm32g4xx_hal::fmac::{
     buffer::{BufferLayout, Watermark},
-    function::IIR,
+    function::{Gain, IIR},
     Buffer, FmacExt,
 };
 
@@ -76,7 +75,7 @@ fn main() -> ! {
     fmac.select_function(IIR {
         feedforward_coeffs: 1,
         feedback_coeffs: 1,
-        gain: 0,
+        gain: Gain::ZeroDB,
     });
 
     let fmac = fmac.start();

src/fmac.rs

@@ -200,7 +200,7 @@ impl<Layout: BufferLayoutConfig> Fmac<Layout, Stopped> {
 
 impl<Layout: BufferLayoutConfig, S: State> Fmac<Layout, S> {
     /// Transition to the next state
-    pub fn next_state() -> Self {
+    fn next_state() -> Self {
         Fmac {
             _phantom: PhantomData,
         }

src/fmac/function.rs

@@ -1,5 +1,19 @@
 //! FMAC Functions
 
+/// Programmable gain parameter in the range 0dB to 42dB in 6dB increments.
+#[repr(u8)]
+#[derive(Copy, Clone)]
+pub enum Gain {
+    ZeroDB = 0,
+    SixDB = 1,
+    TwelveDB = 2,
+    EighteenDB = 3,
+    TwentyFourDB = 4,
+    ThirtyDB = 5,
+    ThirtySixDB = 6,
+    FortyTwoDB = 7,
+}
+
 /// FMAC Function trait. This defines the function specific data that is loaded into the PARAM register
 pub trait Function {
     /// The function ID loaded into the FUNC field
@@ -64,7 +78,8 @@ impl Function for LoadY {
 pub struct Convolution {
     /// Number of coefficients in the X2 buffer
     pub length: u8,
-    pub gain: u8,
+    /// Gain parameter in the range 0dB to 42dB in 6dB increments
+    pub gain: Gain,
 }
 
 /// Finite Impulse Response (FIR) / Convolution / Dot Product function
@@ -78,17 +93,20 @@ impl Function for Convolution {
 
     #[inline(always)]
     fn r(&self) -> Option<u8> {
-        Some(self.gain)
+        Some(self.gain as u8)
     }
 }
 
 /// Infinite Impulse Response (IIR) filter / Multiply Accumulate
 pub struct IIR {
     /// The number of feedforward coefficients in the X2 buffer
+    /// X2 buffer size should be at least 2*feedforward_coeffs + 2*feedback_coeffs
     pub feedforward_coeffs: u8,
     /// The number of feedback coefficients in the X2 buffer
+    /// X2 buffer size should be at least 2*feedforward_coeffs + 2*feedback_coeffs
     pub feedback_coeffs: u8,
-    pub gain: u8,
+    /// Gain parameter in the range 0dB to 42dB in 6dB increments
+    pub gain: Gain,
 }
 
 impl Function for IIR {
@@ -104,6 +122,6 @@ impl Function for IIR {
     }
 
     fn r(&self) -> Option<u8> {
-        Some(self.gain)
+        Some(self.gain as u8)
     }
 }