diff --git a/embassy-stm32/src/pwm/complementary_pwm.rs b/embassy-stm32/src/pwm/complementary_pwm.rs index 13edfbaa..3f8b43cf 100644 --- a/embassy-stm32/src/pwm/complementary_pwm.rs +++ b/embassy-stm32/src/pwm/complementary_pwm.rs @@ -1,7 +1,7 @@ use core::marker::PhantomData; use embassy_hal_common::{into_ref, PeripheralRef}; -pub use stm32_metapac::timer::vals::Ckd; +use stm32_metapac::timer::vals::Ckd; use super::simple_pwm::*; use super::*; @@ -114,11 +114,145 @@ impl<'d, T: ComplementaryCaptureCompare16bitInstance> ComplementaryPwm<'d, T> { unsafe { self.inner.set_compare_value(channel, duty) } } - pub fn set_dead_time_clock_division(&mut self, value: Ckd) { - unsafe { self.inner.set_dead_time_clock_division(value) } - } + /// Set the dead time as a proportion of max_duty + pub fn set_dead_time(&mut self, value: u16) { + let (ckd, value) = compute_dead_time_value(value); - pub fn set_dead_time_value(&mut self, value: u8) { - unsafe { self.inner.set_dead_time_value(value) } + unsafe { + self.inner.set_dead_time_clock_division(ckd); + self.inner.set_dead_time_value(value); + } + } +} + +fn compute_dead_time_value(value: u16) -> (Ckd, u8) { + /* + Dead-time = T_clk * T_dts * T_dtg + + T_dts: + This bit-field indicates the division ratio between the timer clock (CK_INT) frequency and the + dead-time and sampling clock (tDTS)used by the dead-time generators and the digital filters + (ETR, TIx), + 00: tDTS=tCK_INT + 01: tDTS=2*tCK_INT + 10: tDTS=4*tCK_INT + + T_dtg: + This bit-field defines the duration of the dead-time inserted between the complementary + outputs. DT correspond to this duration. + DTG[7:5]=0xx => DT=DTG[7:0]x tdtg with tdtg=tDTS. + DTG[7:5]=10x => DT=(64+DTG[5:0])xtdtg with Tdtg=2xtDTS. + DTG[7:5]=110 => DT=(32+DTG[4:0])xtdtg with Tdtg=8xtDTS. + DTG[7:5]=111 => DT=(32+DTG[4:0])xtdtg with Tdtg=16xtDTS. + Example if TDTS=125ns (8MHz), dead-time possible values are: + 0 to 15875 ns by 125 ns steps, + 16 us to 31750 ns by 250 ns steps, + 32 us to 63us by 1 us steps, + 64 us to 126 us by 2 us steps + */ + + let mut error = u16::MAX; + let mut ckd = Ckd::DIV1; + let mut bits = 0u8; + + for this_ckd in [Ckd::DIV1, Ckd::DIV2, Ckd::DIV4] { + let outdiv = match this_ckd { + Ckd::DIV1 => 1, + Ckd::DIV2 => 2, + Ckd::DIV4 => 4, + _ => unreachable!(), + }; + + // 127 + // 128 + // .. + // 254 + // 256 + // .. + // 504 + // 512 + // .. + // 1008 + + let target = value / outdiv; + let (these_bits, result) = if target < 128 { + (target as u8, target) + } else if target < 255 { + (64 + (target / 2) as u8, (target - target % 2)) + } else if target < 508 { + (32 + (target / 8) as u8, (target - target % 8)) + } else if target < 1008 { + (32 + (target / 16) as u8, (target - target % 16)) + } else { + (u8::MAX, 1008) + }; + + let this_error = value.abs_diff(result * outdiv); + if error > this_error { + ckd = this_ckd; + bits = these_bits; + error = this_error; + } + + match error { + 0 => break, + _ => {} + } + } + + (ckd, bits) +} + +#[cfg(test)] +mod tests { + use super::{compute_dead_time_value, Ckd}; + + #[test] + fn test_compute_dead_time_value() { + struct test_run { + value: u16, + ckd: Ckd, + bits: u8, + } + + let fn_results = [ + test_run { + value: 1, + ckd: Ckd::DIV1, + bits: 1, + }, + test_run { + value: 125, + ckd: Ckd::DIV1, + bits: 125, + }, + test_run { + value: 245, + ckd: Ckd::DIV1, + bits: 64 + 245 / 2, + }, + test_run { + value: 255, + ckd: Ckd::DIV2, + bits: 127, + }, + test_run { + value: 400, + ckd: Ckd::DIV1, + bits: 32 + (400u16 / 8) as u8, + }, + test_run { + value: 600, + ckd: Ckd::DIV4, + bits: 64 + (600u16 / 8) as u8, + }, + ]; + + for test_run in fn_results { + let (ckd, bits) = compute_dead_time_value(test_run.value); + + assert_eq!(ckd.0, test_run.ckd.0); + assert_eq!(bits, test_run.bits); + } } } diff --git a/examples/stm32f4/src/bin/pwm_complementary.rs b/examples/stm32f4/src/bin/pwm_complementary.rs index 6e17f3fd..a8a68ed6 100644 --- a/examples/stm32f4/src/bin/pwm_complementary.rs +++ b/examples/stm32f4/src/bin/pwm_complementary.rs @@ -4,7 +4,7 @@ use defmt::*; use embassy_executor::Spawner; -use embassy_stm32::pwm::complementary_pwm::{Ckd, ComplementaryPwm, ComplementaryPwmPin}; +use embassy_stm32::pwm::complementary_pwm::{ComplementaryPwm, ComplementaryPwmPin}; use embassy_stm32::pwm::simple_pwm::PwmPin; use embassy_stm32::pwm::Channel; use embassy_stm32::time::khz; @@ -31,34 +31,9 @@ async fn main(_spawner: Spawner) { khz(10), ); - /* - Dead-time = T_clk * T_dts * T_dtg - - T_dts: - This bit-field indicates the division ratio between the timer clock (CK_INT) frequency and the - dead-time and sampling clock (tDTS)used by the dead-time generators and the digital filters - (ETR, TIx), - 00: tDTS=tCK_INT - 01: tDTS=2*tCK_INT - 10: tDTS=4*tCK_INT - - T_dtg: - This bit-field defines the duration of the dead-time inserted between the complementary - outputs. DT correspond to this duration. - DTG[7:5]=0xx => DT=DTG[7:0]x tdtg with tdtg=tDTS. - DTG[7:5]=10x => DT=(64+DTG[5:0])xtdtg with Tdtg=2xtDTS. - DTG[7:5]=110 => DT=(32+DTG[4:0])xtdtg with Tdtg=8xtDTS. - DTG[7:5]=111 => DT=(32+DTG[4:0])xtdtg with Tdtg=16xtDTS. - Example if TDTS=125ns (8MHz), dead-time possible values are: - 0 to 15875 ns by 125 ns steps, - 16 us to 31750 ns by 250 ns steps, - 32 us to 63us by 1 us steps, - 64 us to 126 us by 2 us steps - */ - pwm.set_dead_time_clock_division(Ckd::DIV1); - pwm.set_dead_time_value(0); - let max = pwm.get_max_duty(); + pwm.set_dead_time(max / 1024); + pwm.enable(Channel::Ch1); info!("PWM initialized");