From 14e69309ebe25a76f67c38411c7a80a4d83da5ed Mon Sep 17 00:00:00 2001 From: rafael Date: Mon, 21 Oct 2024 22:42:18 +0200 Subject: [PATCH] add pwm frequency to examples --- examples/rp/src/bin/pwm.rs | 10 ++++++++-- examples/rp23/src/bin/pwm.rs | 10 ++++++++-- .../rp23/src/bin/pwm_tb6612fng_motor_driver.rs | 17 +++++++---------- 3 files changed, 23 insertions(+), 14 deletions(-) diff --git a/examples/rp/src/bin/pwm.rs b/examples/rp/src/bin/pwm.rs index 862a7da22..791b88b5b 100644 --- a/examples/rp/src/bin/pwm.rs +++ b/examples/rp/src/bin/pwm.rs @@ -45,8 +45,14 @@ async fn pwm_set_config(slice4: PWM_SLICE4, pin25: PIN_25) { /// Using GP4 in Slice2, make sure to use an appropriate resistor. #[embassy_executor::task] async fn pwm_set_dutycycle(slice2: PWM_SLICE2, pin4: PIN_4) { + // If we aim for a specific frequency, here is how we can calculate the top value. + // The top value sets the period of the PWM cycle, so a counter goes from 0 to top and then wraps around to 0. + // Every such wraparound is one PWM cycle. So here is how we get 25KHz: let mut c = Config::default(); - c.top = 32_768; + let pwm_freq = 25_000; // Hz, our desired frequency + let clock_freq = embassy_rp::clocks::clk_sys_freq(); + c.top = (clock_freq / pwm_freq) as u16 - 1; + let mut pwm = Pwm::new_output_a(slice2, pin4, c.clone()); loop { @@ -59,7 +65,7 @@ async fn pwm_set_dutycycle(slice2: PWM_SLICE2, pin4: PIN_4) { Timer::after_secs(1).await; // 25% duty cycle. Expressed as 32768/4 = 8192. - pwm.set_duty_cycle(8_192).unwrap(); + pwm.set_duty_cycle(c.top / 4).unwrap(); Timer::after_secs(1).await; // 0% duty cycle, fully off. diff --git a/examples/rp23/src/bin/pwm.rs b/examples/rp23/src/bin/pwm.rs index 838eee625..5a4457158 100644 --- a/examples/rp23/src/bin/pwm.rs +++ b/examples/rp23/src/bin/pwm.rs @@ -50,8 +50,14 @@ async fn pwm_set_config(slice4: PWM_SLICE4, pin25: PIN_25) { /// Using GP4 in Slice2, make sure to use an appropriate resistor. #[embassy_executor::task] async fn pwm_set_dutycycle(slice2: PWM_SLICE2, pin4: PIN_4) { + // If we aim for a specific frequency, here is how we can calculate the top value. + // The top value sets the period of the PWM cycle, so a counter goes from 0 to top and then wraps around to 0. + // Every such wraparound is one PWM cycle. So here is how we get 25KHz: let mut c = Config::default(); - c.top = 32_768; + let pwm_freq = 25_000; // Hz, our desired frequency + let clock_freq = embassy_rp::clocks::clk_sys_freq(); + c.top = (clock_freq / pwm_freq) as u16 - 1; + let mut pwm = Pwm::new_output_a(slice2, pin4, c.clone()); loop { @@ -64,7 +70,7 @@ async fn pwm_set_dutycycle(slice2: PWM_SLICE2, pin4: PIN_4) { Timer::after_secs(1).await; // 25% duty cycle. Expressed as 32768/4 = 8192. - pwm.set_duty_cycle(8_192).unwrap(); + pwm.set_duty_cycle(c.top / 4).unwrap(); Timer::after_secs(1).await; // 0% duty cycle, fully off. diff --git a/examples/rp23/src/bin/pwm_tb6612fng_motor_driver.rs b/examples/rp23/src/bin/pwm_tb6612fng_motor_driver.rs index 6c3a8998c..263b551de 100644 --- a/examples/rp23/src/bin/pwm_tb6612fng_motor_driver.rs +++ b/examples/rp23/src/bin/pwm_tb6612fng_motor_driver.rs @@ -16,12 +16,6 @@ use embassy_time::{Duration, Timer}; use tb6612fng::{DriveCommand, Motor, Tb6612fng}; use {defmt_rtt as _, panic_probe as _}; -/// Maximum PWM value (fully on) -const PWM_MAX: u16 = 50000; - -/// Minimum PWM value (fully off) -const PWM_MIN: u16 = 0; - #[link_section = ".start_block"] #[used] pub static IMAGE_DEF: ImageDef = ImageDef::secure_exe(); @@ -46,6 +40,11 @@ async fn main(_spawner: Spawner) { let s = split_resources!(p); let r = s.motor; + // we want a PWM frequency of 25KHz + let pwm_freq = 25_000; // Hz, our desired frequency + let clock_freq = embassy_rp::clocks::clk_sys_freq(); + let period = (clock_freq / pwm_freq) as u16 - 1; + // we need a standby output and two motors to construct a full TB6612FNG // standby pin @@ -55,8 +54,7 @@ async fn main(_spawner: Spawner) { let left_fwd = gpio::Output::new(r.left_forward_pin, gpio::Level::Low); let left_bckw = gpio::Output::new(r.left_backward_pin, gpio::Level::Low); let mut left_speed = pwm::Config::default(); - left_speed.top = PWM_MAX; - left_speed.compare_a = PWM_MIN; + left_speed.top = period; let left_pwm = pwm::Pwm::new_output_a(r.left_slice, r.left_pwm_pin, left_speed); let left_motor = Motor::new(left_fwd, left_bckw, left_pwm).unwrap(); @@ -64,8 +62,7 @@ async fn main(_spawner: Spawner) { let right_fwd = gpio::Output::new(r.right_forward_pin, gpio::Level::Low); let right_bckw = gpio::Output::new(r.right_backward_pin, gpio::Level::Low); let mut right_speed = pwm::Config::default(); - right_speed.top = PWM_MAX; - right_speed.compare_b = PWM_MIN; + right_speed.top = period; let right_pwm = pwm::Pwm::new_output_b(r.right_slice, r.right_pwm_pin, right_speed); let right_motor = Motor::new(right_fwd, right_bckw, right_pwm).unwrap();