Cleaning up conversion + comments

This commit is contained in:
Ryan Summers 2021-05-10 11:10:26 +02:00
parent 65eb74b31e
commit fa886d2eac
4 changed files with 7 additions and 25 deletions

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@ -26,8 +26,6 @@ pub struct Settings {
iir_ch: [[iir::IIR; IIR_CASCADE_LENGTH]; 2], iir_ch: [[iir::IIR; IIR_CASCADE_LENGTH]; 2],
allow_hold: bool, allow_hold: bool,
force_hold: bool, force_hold: bool,
// The telemetry period in seconds.
telemetry_period: u16, telemetry_period: u16,
} }
@ -46,6 +44,7 @@ impl Default for Settings {
allow_hold: false, allow_hold: false,
// Force suppress filter output updates. // Force suppress filter output updates.
force_hold: false, force_hold: false,
// The default telemetry period in seconds.
telemetry_period: 10, telemetry_period: 10,
} }
} }

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@ -56,8 +56,6 @@ pub struct Settings {
lockin_phase: i32, lockin_phase: i32,
output_conf: [Conf; 2], output_conf: [Conf; 2],
// The telemetry period in seconds.
telemetry_period: u16, telemetry_period: u16,
} }
@ -75,6 +73,7 @@ impl Default for Settings {
lockin_phase: 0, // Demodulation LO phase offset lockin_phase: 0, // Demodulation LO phase offset
output_conf: [Conf::InPhase, Conf::Quadrature], output_conf: [Conf::InPhase, Conf::Quadrature],
// The default telemetry period in seconds.
telemetry_period: 10, telemetry_period: 10,
} }
} }

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@ -92,14 +92,10 @@ impl Into<f32> for AdcCode {
/// Convert raw ADC codes to/from voltage levels. /// Convert raw ADC codes to/from voltage levels.
/// ///
/// # Note /// # Note
///
/// This does not account for the programmable gain amplifier at the signal input. /// This does not account for the programmable gain amplifier at the signal input.
fn into(self) -> f32 { fn into(self) -> f32 {
// The input voltage is measured by the ADC across a dynamic scale of +/- 4.096 V with a // The ADC has a differential input with a range of +/- 4.096 V and 16-bit resolution.
// dynamic range across signed integers. Additionally, the signal is fully differential, so // The gain into the two inputs is 1/5.
// the differential voltage is measured at the ADC. Thus, the single-ended signal is
// measured at the input is half of the ADC-reported measurement. As a pre-filter, the
// input signal has a fixed gain of 1/5 through a static input active filter.
let adc_volts_per_lsb = 5.0 / 2.0 * 4.096 / i16::MAX as f32; let adc_volts_per_lsb = 5.0 / 2.0 * 4.096 / i16::MAX as f32;
(self.0 as i16) as f32 * adc_volts_per_lsb (self.0 as i16) as f32 * adc_volts_per_lsb

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@ -76,28 +76,16 @@ pub struct DacCode(pub u16);
impl Into<f32> for DacCode { impl Into<f32> for DacCode {
fn into(self) -> f32 { fn into(self) -> f32 {
// The output voltage is generated by the DAC with an output range of +/- 4.096 V. This // The DAC output range in bipolar mode (including the external output op-amp) is +/- 4.096
// signal then passes through a 2.5x gain stage. Note that the DAC operates using unsigned // V with 16-bit resolution. The anti-aliasing filter has an additional gain of 2.5.
// integers, and u16::MAX / 2 is considered zero voltage output. Thus, the dynamic range of
// the output stage is +/- 10.24 V. At a DAC code of zero, there is an output of -10.24 V,
// and at a max DAC code, there is an output of (slightly less than) 10.24 V.
let dac_volts_per_lsb = 4.096 * 2.5 / (1u16 << 15) as f32; let dac_volts_per_lsb = 4.096 * 2.5 / (1u16 << 15) as f32;
// Note that the bipolar table is an offset-binary code, but it is much more logical and
// correct to treat it as a twos-complement value. TO do that, we XOR the most significant
// bit to convert it.
(self.0 ^ 0x8000) as i16 as f32 * dac_volts_per_lsb (self.0 ^ 0x8000) as i16 as f32 * dac_volts_per_lsb
} }
} }
impl From<i16> for DacCode { impl From<i16> for DacCode {
/// Generate a DAC code from a 16-bit signed value. /// Encode signed 16-bit values into DAC offset binary for a bipolar output configuration.
///
/// # Note
/// This is provided as a means to convert between the DACs internal 16-bit, unsigned register
/// and a 2s-complement integer that is convenient when using the DAC in the bipolar
/// configuration.
fn from(value: i16) -> Self { fn from(value: i16) -> Self {
Self(value as u16 ^ 0x8000) Self(value as u16 ^ 0x8000)
} }