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stm32/pwm: improve dead-time api

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This commit is contained in:
xoviat 2023-05-01 16:42:03 -05:00
parent 7646f18836
commit cd88e39f5f
2 changed files with 143 additions and 34 deletions
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146
embassy-stm32/src/pwm/complementary_pwm.rs
View file

@ -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);
}
}
}

31
examples/stm32f4/src/bin/pwm_complementary.rs
View file

@ -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");