a little piece of code doing 1000Hz Sawtooth synthesis via PWM

pwm_dac_saw_sampling/.cargo/config

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+[target.'cfg(all(target_arch = "arm", target_os = "none"))']
+runner = "probe-run-rp --chip RP2040"
+
+rustflags = [
+  "-C", "linker=flip-link",
+  "-C", "link-arg=--nmagic",
+  "-C", "link-arg=-Tlink.x",
+  "-C", "link-arg=-Tdefmt.x",
+
+  # Code-size optimizations.
+  #   trap unreachable can save a lot of space, but requires nightly compiler.
+  #   uncomment the next line if you wish to enable it
+  # "-Z", "trap-unreachable=no",
+  "-C", "inline-threshold=5",
+  "-C", "no-vectorize-loops",
+]
+
+[build]
+target = "thumbv6m-none-eabi"

pwm_dac_saw_sampling/.gitignore

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+**/*.rs.bk
+.#*
+.gdb_history
+Cargo.lock
+target/
+
+# editor files
+.vscode/*
+!.vscode/*.md
+!.vscode/*.svd
+!.vscode/launch.json
+!.vscode/tasks.json
+!.vscode/extensions.json
+!.vscode/settings.json
+
+*.history

pwm_dac_saw_sampling/.vscode/settings.json

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+{
+    "editor.formatOnSave": true
+}

pwm_dac_saw_sampling/Cargo.toml

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+[package]
+authors = ["the rp-rs team"]
+edition = "2018"
+readme = "README.md"
+name = "rp2040-project-template"
+version = "0.1.0"
+resolver = "2"
+
+[dependencies]
+cortex-m = "0.7.3"
+cortex-m-rt = "0.7.0"
+embedded-hal = { version = "0.2.5", features=["unproven"] }
+embedded-time = "0.12.0"
+
+defmt = "0.2.0"
+defmt-rtt = "0.2.0"
+panic-probe = { version = "0.2.0", features = ["print-defmt"] }
+
+rp2040-hal = { git = "https://github.com/rp-rs/rp-hal", branch="main", features=["rt"] }
+rp2040-boot2 = { git = "https://github.com/rp-rs/rp2040-boot2-rs", branch="main" }
+
+nb = "1.0"
+
+[features]
+default = [
+    "defmt-default",
+]
+defmt-default = []
+defmt-trace = []
+defmt-debug = []
+defmt-info = []
+defmt-warn = []
+defmt-error = []
+
+# cargo build/run
+[profile.dev]
+codegen-units = 1
+debug = 2
+debug-assertions = true
+incremental = false
+opt-level = 3
+overflow-checks = true
+
+# cargo build/run --release
+[profile.release]
+codegen-units = 1
+debug = 2
+debug-assertions = false
+incremental = false
+lto = 'fat'
+opt-level = 3
+overflow-checks = false
+
+# do not optimize proc-macro crates = faster builds from scratch
+[profile.dev.build-override]
+codegen-units = 8
+debug = false
+debug-assertions = false
+opt-level = 0
+overflow-checks = false
+
+[profile.release.build-override]
+codegen-units = 8
+debug = false
+debug-assertions = false
+opt-level = 0
+overflow-checks = false
+
+# cargo test
+[profile.test]
+codegen-units = 1
+debug = 2
+debug-assertions = true
+incremental = false
+opt-level = 3
+overflow-checks = true
+
+# cargo test --release
+[profile.bench]
+codegen-units = 1
+debug = 2
+debug-assertions = false
+incremental = false
+lto = 'fat'
+opt-level = 3

pwm_dac_saw_sampling/build.rs

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+//! This build script copies the `memory.x` file from the crate root into
+//! a directory where the linker can always find it at build time.
+//! For many projects this is optional, as the linker always searches the
+//! project root directory -- wherever `Cargo.toml` is. However, if you
+//! are using a workspace or have a more complicated build setup, this
+//! build script becomes required. Additionally, by requesting that
+//! Cargo re-run the build script whenever `memory.x` is changed,
+//! updating `memory.x` ensures a rebuild of the application with the
+//! new memory settings.
+
+use std::env;
+use std::fs::File;
+use std::io::Write;
+use std::path::PathBuf;
+
+fn main() {
+    // Put `memory.x` in our output directory and ensure it's
+    // on the linker search path.
+    let out = &PathBuf::from(env::var_os("OUT_DIR").unwrap());
+    File::create(out.join("memory.x"))
+        .unwrap()
+        .write_all(include_bytes!("memory.x"))
+        .unwrap();
+    println!("cargo:rustc-link-search={}", out.display());
+
+    // By default, Cargo will re-run a build script whenever
+    // any file in the project changes. By specifying `memory.x`
+    // here, we ensure the build script is only re-run when
+    // `memory.x` is changed.
+    println!("cargo:rerun-if-changed=memory.x");
+}

pwm_dac_saw_sampling/memory.x

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+MEMORY {
+    BOOT2 : ORIGIN = 0x10000000, LENGTH = 0x100
+    FLASH : ORIGIN = 0x10000100, LENGTH = 2048K - 0x100
+    RAM   : ORIGIN = 0x20000000, LENGTH = 256K
+}
+
+SECTIONS {
+    /* ### Boot loader */
+    .boot2 ORIGIN(BOOT2) :
+    {
+        KEEP(*(.boot2));
+    } > BOOT2
+} INSERT BEFORE .text;

pwm_dac_saw_sampling/src/example_1000hz_saw.rs

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+#![no_std]
+#![no_main]
+
+use cortex_m_rt::entry;
+use defmt::*;
+use defmt_rtt as _;
+use embedded_hal::timer::CountDown;
+use embedded_hal::PwmPin;
+use embedded_time::duration::*;
+use panic_probe as _;
+use rp2040_hal as hal;
+
+use hal::{
+    clocks::{init_clocks_and_plls},
+    pac,
+    sio::Sio,
+    watchdog::Watchdog,
+};
+
+#[link_section = ".boot2"]
+#[used]
+pub static BOOT2: [u8; 256] = rp2040_boot2::BOOT_LOADER_W25Q080;
+
+#[entry]
+fn main() -> ! {
+    info!("Program start");
+    let mut pac      = pac::Peripherals::take().unwrap();
+    let _core         = pac::CorePeripherals::take().unwrap();
+    let mut watchdog = Watchdog::new(pac.WATCHDOG);
+    let sio          = Sio::new(pac.SIO);
+
+    // External high-speed crystal on the pico board is 12Mhz
+    let external_xtal_freq_hz = 12_000_000u32;
+    let _clocks =
+        init_clocks_and_plls(
+            external_xtal_freq_hz,
+            pac.XOSC,
+            pac.CLOCKS,
+            pac.PLL_SYS,
+            pac.PLL_USB,
+            &mut pac.RESETS,
+            &mut watchdog)
+        .ok()
+        .unwrap();
+
+    let timer = hal::timer::Timer::new(pac.TIMER, &mut pac.RESETS);
+    let mut cnt_down = timer.count_down();
+
+    let mut pwm_slices = hal::pwm::Slices::new(pac.PWM, &mut pac.RESETS);
+
+    let pwm = &mut pwm_slices.pwm7;
+    pwm.enable();
+    pwm.set_div_int(1);
+    pwm.set_div_frac(0);
+
+    let pins =
+        hal::gpio::Pins::new(
+            pac.IO_BANK0, pac.PADS_BANK0, sio.gpio_bank0, &mut pac.RESETS);
+
+    let top = 200; // changing this changes the PWM frequency!
+    pwm.set_top(top);
+
+    let channel = &mut pwm.channel_b;
+    channel.output_to(pins.gpio15);
+
+    let mut phase = 0.0;
+    loop {
+        cnt_down.start((25_u32).microseconds());
+
+        channel.set_duty((phase * top as f32) as u16);
+
+        phase = phase + (1000.0 / 40000.0);
+        while phase > 1.0 { phase -= 1.0; }
+
+        let _ = nb::block!(cnt_down.wait());
+    }
+}
+
+
+
+
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+
+
+
+//    let mut delay =
+//        cortex_m::delay::Delay::new(
+//            core.SYST,
+//            clocks.system_clock.freq().integer());
+
+
+//    let mut led_pin = pins.gpio25.into_push_pull_output();
+//        info!("on!");
+//        led_pin.set_high().unwrap();
+//        info!("off!");
+//        led_pin.set_low().unwrap();
+
+//        duty = (duty + 1) % (steps + 1);
+//        channel.set_duty(duty * tPs);
+//        let h = rp2040_hal::rom_data::float_funcs::fsin(
+//            phase * 3.14159265359 * 2.0);

pwm_dac_saw_sampling/src/main.rs

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+#![no_std]
+#![no_main]
+
+use cortex_m_rt::entry;
+use defmt::*;
+use defmt_rtt as _;
+use embedded_hal::timer::CountDown;
+use embedded_hal::PwmPin;
+use embedded_time::duration::*;
+use panic_probe as _;
+use rp2040_hal as hal;
+
+use hal::{
+    clocks::{init_clocks_and_plls},
+    pac,
+    sio::Sio,
+    watchdog::Watchdog,
+};
+
+#[link_section = ".boot2"]
+#[used]
+pub static BOOT2: [u8; 256] = rp2040_boot2::BOOT_LOADER_W25Q080;
+
+#[entry]
+fn main() -> ! {
+    info!("Program start");
+    let mut pac      = pac::Peripherals::take().unwrap();
+    let _core         = pac::CorePeripherals::take().unwrap();
+    let mut watchdog = Watchdog::new(pac.WATCHDOG);
+    let sio          = Sio::new(pac.SIO);
+
+    // External high-speed crystal on the pico board is 12Mhz
+    let external_xtal_freq_hz = 12_000_000u32;
+    let _clocks =
+        init_clocks_and_plls(
+            external_xtal_freq_hz,
+            pac.XOSC,
+            pac.CLOCKS,
+            pac.PLL_SYS,
+            pac.PLL_USB,
+            &mut pac.RESETS,
+            &mut watchdog)
+        .ok()
+        .unwrap();
+
+    let timer = hal::timer::Timer::new(pac.TIMER, &mut pac.RESETS);
+    let mut cnt_down = timer.count_down();
+
+    let mut pwm_slices = hal::pwm::Slices::new(pac.PWM, &mut pac.RESETS);
+
+    let pwm = &mut pwm_slices.pwm7;
+    pwm.enable();
+    pwm.set_div_int(1);
+    pwm.set_div_frac(0);
+
+    let pins =
+        hal::gpio::Pins::new(
+            pac.IO_BANK0, pac.PADS_BANK0, sio.gpio_bank0, &mut pac.RESETS);
+
+    let top = 200; // changing this changes the PWM frequency!
+    pwm.set_top(top);
+
+    let channel = &mut pwm.channel_b;
+    channel.output_to(pins.gpio15);
+
+    let mut phase = 0.0;
+    loop {
+        cnt_down.start((25_u32).microseconds());
+
+        channel.set_duty((phase * top as f32) as u16);
+
+        phase = phase + (1000.0 / 40000.0);
+        while phase > 1.0 { phase -= 1.0; }
+
+        let _ = nb::block!(cnt_down.wait());
+    }
+}
+
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+
+
+//    let mut delay =
+//        cortex_m::delay::Delay::new(
+//            core.SYST,
+//            clocks.system_clock.freq().integer());
+
+
+//    let mut led_pin = pins.gpio25.into_push_pull_output();
+//        info!("on!");
+//        led_pin.set_high().unwrap();
+//        info!("off!");
+//        led_pin.set_low().unwrap();
+
+//        duty = (duty + 1) % (steps + 1);
+//        channel.set_duty(duty * tPs);
+//        let h = rp2040_hal::rom_data::float_funcs::fsin(
+//            phase * 3.14159265359 * 2.0);