pounder_test/src/hardware/signal_generator.rs

use crate::hardware::{dac::DacCode, design_parameters::ADC_SAMPLE_TICKS};
use miniconf::Miniconf;
use serde::Deserialize;

#[derive(Copy, Clone, Debug, Deserialize, Miniconf)]
pub enum Signal {
    Cosine,
    Square,
    Triangle,
}

#[derive(Copy, Clone, Debug, Miniconf, Deserialize)]
pub struct BasicConfig {
    pub frequency: f32,
    pub asymmetry: f32,
    pub signal: Signal,
    pub amplitude: f32,
}

impl Default for BasicConfig {
    fn default() -> Self {
        Self {
            frequency: 1.0e3,
            asymmetry: 0.0,
            signal: Signal::Cosine,
            amplitude: 0.0,
        }
    }
}

impl From<BasicConfig> for Config {
    fn from(config: BasicConfig) -> Config {
        // Calculate the frequency tuning word
        let frequency: u32 = {
            let conversion_factor =
                ADC_SAMPLE_TICKS as f32 / 100.0e6 * (1u64 << 32) as f32;
            (config.frequency * conversion_factor) as u32
        };

        // Clamp amplitude and symmetry.
        let amplitude = if config.amplitude > 10.24 {
            10.24
        } else if config.amplitude < 0.0 {
            0.0
        } else {
            config.amplitude
        };

        let symmetry = {
            let asymmetry = if config.asymmetry < -1.0 {
                -1.0
            } else if config.asymmetry > 1.0 {
                1.0
            } else {
                config.asymmetry
            };

            (asymmetry * i32::MAX as f32) as i32
        };

        let signal_config = match config.signal {
            Signal::Cosine => SignalConfig::Cosine,
            Signal::Square => SignalConfig::Square { symmetry },
            Signal::Triangle => {
                let tuning_word = {
                    let segment_one_turns =
                        symmetry.wrapping_sub(i32::MIN) >> 16;
                    let segment_one_tw = if segment_one_turns > 0 {
                        u16::MAX as u32 / segment_one_turns as u32
                    } else {
                        0
                    };

                    let segment_two_turns =
                        i32::MAX.wrapping_sub(symmetry) >> 16;
                    let segment_two_tw = if segment_two_turns > 0 {
                        u16::MAX as u32 / segment_two_turns as u32
                    } else {
                        0
                    };

                    [segment_one_tw, segment_two_tw]
                };

                SignalConfig::Triangle {
                    symmetry,
                    tuning_word,
                }
            }
        };

        Config {
            amplitude: DacCode::from(amplitude).into(),
            signal: signal_config,
            frequency,
        }
    }
}

#[derive(Copy, Clone, Debug)]
pub struct Config {
    /// The type of signal being generated
    pub signal: SignalConfig,

    /// The full-scale output code of the signal
    pub amplitude: i16,

    /// The frequency tuning word of the signal. Phase is incremented by this amount
    pub frequency: u32,
}

#[derive(Copy, Clone, Debug)]
pub enum SignalConfig {
    Cosine,
    Square {
        /// The phase symmetry cross-over of the waveform.
        symmetry: i32,
    },
    Triangle {
        /// The phase symmetry cross-over of the waveform.
        symmetry: i32,
        /// The amplitude added for each phase turn increment (different words for different
        /// phases).
        tuning_word: [u32; 2],
    },
}

#[derive(Debug)]
pub struct SignalGenerator {
    phase_accumulator: u32,
    config: Config,
    pending_config: Option<Config>,
}

impl Default for SignalGenerator {
    fn default() -> Self {
        Self {
            config: BasicConfig::default().into(),
            phase_accumulator: 0,
            pending_config: None,
        }
    }
}

impl SignalGenerator {
    /// Construct a new signal generator with some specific config.
    ///
    /// # Args
    /// * `config` - The config to use for generating signals.
    ///
    /// # Returns
    /// The generator
    pub fn new(config: impl Into<Config>) -> Self {
        Self {
            config: config.into(),
            pending_config: None,
            phase_accumulator: 0,
        }
    }

    // Increment the phase of the signal.
    //
    // # Note
    // This handles automatically applying pending configurations on phase wrap.
    //
    // # Returns
    // The new phase to use
    fn increment(&mut self) -> i32 {
        let (phase, overflow) = self
            .phase_accumulator
            .overflowing_add(self.config.frequency);

        self.phase_accumulator = phase;

        // Special case: If the FTW is specified as zero, we would otherwise never update the
        // settings. Perform a check here for this corner case.
        if overflow || self.config.frequency == 0 {
            if let Some(config) = self.pending_config.take() {
                self.config = config;
                self.phase_accumulator = 0;
            }
        }

        self.phase_accumulator as i32
    }

    /// Update waveform generation settings.
    ///
    /// # Note
    /// Changes will not take effect until the current waveform period elapses.
    pub fn update_waveform(&mut self, new_config: impl Into<Config>) {
        self.pending_config = Some(new_config.into());
    }
}

impl core::iter::Iterator for SignalGenerator {
    type Item = i16;

    /// Get the next value in the generator sequence.
    fn next(&mut self) -> Option<i16> {
        let phase = self.increment();

        let amplitude = match self.config.signal {
            SignalConfig::Cosine => (dsp::cossin(phase).0 >> 16) as i16,
            SignalConfig::Square { symmetry } => {
                if phase < symmetry {
                    i16::MAX
                } else {
                    i16::MIN
                }
            }
            SignalConfig::Triangle {
                symmetry,
                tuning_word,
            } => {
                if phase < symmetry {
                    let segment_turns =
                        (phase.wrapping_sub(i32::MIN) >> 16) as u16;
                    i16::MIN.wrapping_add(
                        (tuning_word[0] * segment_turns as u32) as i16,
                    )
                } else {
                    let segment_turns =
                        (phase.wrapping_sub(symmetry) >> 16) as u16;
                    i16::MAX.wrapping_sub(
                        (tuning_word[1] * segment_turns as u32) as i16,
                    )
                }
            }
        };

        // Calculate the final output result as an i16.
        let result = amplitude as i32 * self.config.amplitude as i32;

        // Note: We downshift by 15-bits to preserve only one of the sign bits.
        Some((result >> 15) as i16)
    }
}