exercises rtic_bare6/7 wip

examples/rtic_bare6.rs

+//! rtic_bare6.rs
+//!
+//! Clocking
+//!
+//! What it covers:
+//! - using svd2rust generated API
+//! - using the stm32f4xx-hal to set clocks
+//! - routing the clock to a PIN for monitoring by an oscilloscope
+
+#![no_main]
+#![no_std]
+
+use panic_rtt_target as _;
+use rtic::cyccnt::{Instant, U32Ext as _};
+use rtt_target::{rprintln, rtt_init_print};
+use stm32f4xx_hal::{
+    prelude::*,
+    stm32::{self, GPIOC, RCC},
+};
+
+const OFFSET: u32 = 8_000_000;
+
+#[rtic::app(device = stm32f4xx_hal::stm32, monotonic = rtic::cyccnt::CYCCNT, peripherals = true)]
+const APP: () = {
+    struct Resources {
+        // late resources
+        GPIOA: stm32::GPIOA,
+    }
+    #[init(schedule = [toggle])]
+    fn init(cx: init::Context) -> init::LateResources {
+        rtt_init_print!();
+        rprintln!("init");
+
+        let mut core = cx.core;
+        let device = cx.device;
+
+        // Initialize (enable) the monotonic timer (CYCCNT)
+        core.DCB.enable_trace();
+        core.DWT.enable_cycle_counter();
+
+        // semantically, the monotonic timer is frozen at time "zero" during `init`
+        // NOTE do *not* call `Instant::now` in this context; it will return a nonsense value
+        let now = cx.start; // the start time of the system
+
+        // Schedule `toggle` to run 8e6 cycles (clock cycles) in the future
+        cx.schedule.toggle(now + OFFSET.cycles()).unwrap();
+
+        // setup LED
+        // power on GPIOA, RM0368 6.3.11
+        device.RCC.ahb1enr.modify(|_, w| w.gpioaen().set_bit());
+        // configure PA5 as output, RM0368 8.4.1
+        device.GPIOA.moder.modify(|_, w| w.moder5().bits(1));
+
+        clock_out(&device.RCC, &device.GPIOC);
+
+        let rcc = device.RCC.constrain();
+
+        let _clocks = rcc.cfgr.freeze();
+
+        // Set up the system clock. 48 MHz?
+        // let _clocks = rcc
+        //     .cfgr
+        //     .sysclk(48.mhz())
+        //     .pclk1(24.mhz())
+        //     .freeze();
+
+        // pass on late resources
+        init::LateResources {
+            GPIOA: device.GPIOA,
+        }
+    }
+
+    #[idle]
+    fn idle(_cx: idle::Context) -> ! {
+        rprintln!("idle");
+        loop {
+            continue;
+        }
+    }
+
+    #[task(resources = [GPIOA], schedule = [toggle])]
+    fn toggle(cx: toggle::Context) {
+        static mut TOGGLE: bool = false;
+        rprintln!("toggle  @ {:?}", Instant::now());
+
+        if *TOGGLE {
+            cx.resources.GPIOA.bsrr.write(|w| w.bs5().set_bit());
+        } else {
+            cx.resources.GPIOA.bsrr.write(|w| w.br5().set_bit());
+        }
+
+        *TOGGLE = !*TOGGLE;
+        cx.schedule.toggle(cx.scheduled + OFFSET.cycles()).unwrap();
+    }
+
+    extern "C" {
+        fn EXTI0();
+    }
+};
+
+// see the Reference Manual RM0368 (www.st.com/resource/en/reference_manual/dm00096844.pdf)
+// rcc,     chapter 6
+// gpio,    chapter 8
+
+fn clock_out(rcc: &RCC, gpioc: &GPIOC) {
+    // output MCO2 to pin PC9
+
+    // mco2 	: SYSCLK = 0b00
+    // mcopre 	: divide by 4 = 0b110
+    rcc.cfgr
+        .modify(|_, w| unsafe { w.mco2().bits(0b00).mco2pre().bits(0b110) });
+
+    // power on GPIOC, RM0368 6.3.11
+    rcc.ahb1enr.modify(|_, w| w.gpiocen().set_bit());
+
+    // MCO_2 alternate function AF0, STM32F401xD STM32F401xE data sheet
+    // table 9
+    // AF0, gpioc reset value = AF0
+
+    // configure PC9 as alternate function 0b10, RM0368 6.2.10
+    gpioc.moder.modify(|_, w| w.moder9().bits(0b10));
+
+    // otyper reset state push/pull, in reset state (don't need to change)
+
+    // ospeedr 0b11 = very high speed
+    gpioc.ospeedr.modify(|_, w| w.ospeedr9().bits(0b11));
+}
+
+// 1. In this example you will use RTT.
+//
+//    > cargo run --example rtic_bare6
+//
+//    Confirm that your RTT traces the init, idle and led on/off.
+//
+//    What is the (default) MCU (SYSCLK) frequency?
+//
+//    ** your answer here **
+//
+//    What is the (default) DWT CYCCNT frequency?
+//
+//    ** your answer here **
+//
+//    What is the frequency of blinking?
+//
+//    ** your answer here **
+//
+//    commit your answers (bare6_1)
+//
+// 2. Now connect an oscilloscope to PC9, which is set to
+//    output the MCO2.
+//
+//    Compute the value of SYSCLK based on the oscilloscope reading
+//
+//    ** your answer here **
+//
+//    What is the peak to peak (voltage) reading of the signal?
+//
+//    ** your answer here **
+//
+//    Make a folder called "pictures" in your git project.
+//    Make a screen dump or photo of the oscilloscope output.
+//    Save the the picture as "bare_6_16mhz_high_speed".
+//
+//    Commit your answers (bare6_2)
+//
+// 3. Now run the example in 48Mz, by commenting out line 56, and un-commenting
+//    lines 58-63.
+//`
+//    What is the frequency of blinking?
+//
+//    ** your answer here **
+//
+//    Commit your answers (bare6_3)
+//
+//    Now change the constant `OFFSET` so you get the same blinking frequency as in 1.
+//    Test and validate that you got the desired behavior.
+//
+//    Commit your answers (bare6_3)
+//
+// 4. Repeat experiment 2
+//
+//    What is the frequency of MCO2 read by the oscilloscope?
+//
+//    ** your answer here **
+//
+//    Compute the value of SYSCLK based on the oscilloscope reading.
+//
+//    ** your answer here **
+//
+//    What is the peak to peak reading of the signal?
+//
+//    ** your answer here **
+//
+//    Make a screen dump or photo of the oscilloscope output.
+//    Save the the picture as "bare_6_64mhz_high_speed".
+//
+//    Commit your answers (bare6_4)
+//
+// 5. In the `clock_out` function, the setup of registers is done through
+//    setting bit-pattens manually, e.g.
+//     rcc.cfgr
+//        .modify(|_, w| unsafe { w.mco2().bits(0b00).mco2pre().bits(0b110) });
+//
+//    However based on the vendor SVD file the svd2rust API provides
+//    a better abstraction, based on pattern enums and functions.
+//
+//    To view the API you can generate documentation for your crate:
+//
+//    > cargo doc --open
+//
+//    By searching for `mco2` you find the enumerations and functions.
+//    So here
+//       `w.mco2().bits{0b00}` is equivalent to
+//       `w.mco2().sysclk()` and improves readability.
+//
+//    Replace all bit-patterns used by the function name equivalents.
+//
+//    Test that the application still runs as before.
+//
+//    Commit your code (bare6_5)
+//
+// 6. Discussion
+//
+//    In this exercise, you have learned to use the stm32f4xx-hal
+//    to set the clock speed of your MCU.
+//
+//    You have also learned how you can monitor/validate MCU clock(s) on pin(s)
+//    connected to an oscilloscope.
+//
+//    You have also learned how you can improve readability of your code
+//    by leveraging the abstractions provided by the PAC.
+//
+//    As mentioned before the PACs are machine generated by `svd2rust`
+//    from vendor provided System View Desciptions (SVDs).
+//
+//    The PACs provide low level peripheral access abstractions, while
+//    the HALs provide higher level abstractions and functionality.

examples/rtic_bare7.rs

+//! rtic_bare7.rs
+//!
+//! Clocking
+//!
+//! What it covers:
+//! - using embedded hal, and the OutputPin abstraction
+
+use panic_rtt_target as _;
+use rtic::cyccnt::{Instant, U32Ext as _};
+use rtt_target::{rprintln, rtt_init_print};
+use stm32f4xx_hal::stm32;
+
+const OFFSET: u32 = 8_000_000;
+
+#[rtic::app(device = stm32f4xx_hal::stm32, monotonic = rtic::cyccnt::CYCCNT, peripherals = true)]
+const APP: () = {
+    struct Resources {
+        // late resources
+        GPIOA: stm32::GPIOA,
+    }
+    #[init(schedule = [toggle])]
+    fn init(cx: init::Context) -> init::LateResources {
+        rtt_init_print!();
+        rprintln!("init");
+
+        let mut core = cx.core;
+        let device = cx.device;
+
+        // Initialize (enable) the monotonic timer (CYCCNT)
+        core.DCB.enable_trace();
+        core.DWT.enable_cycle_counter();
+
+        // semantically, the monotonic timer is frozen at time "zero" during `init`
+        // NOTE do *not* call `Instant::now` in this context; it will return a nonsense value
+        let now = cx.start; // the start time of the system
+
+        // Schedule `toggle` to run 8e6 cycles (clock cycles) in the future
+        cx.schedule.toggle(now + OFFSET.cycles()).unwrap();
+
+        // power on GPIOA, RM0368 6.3.11
+        device.RCC.ahb1enr.modify(|_, w| w.gpioaen().set_bit());
+        // configure PA5 as output, RM0368 8.4.1
+        device.GPIOA.moder.modify(|_, w| w.moder5().bits(1));
+
+        // pass on late resources
+        init::LateResources {
+            GPIOA: device.GPIOA,
+        }
+    }
+
+    #[idle]
+    fn idle(_cx: idle::Context) -> ! {
+        rprintln!("idle");
+        loop {
+            continue;
+        }
+    }
+
+    #[task(resources = [GPIOA], schedule = [toggle])]
+    fn toggle(cx: toggle::Context) {
+        static mut TOGGLE: bool = false;
+        rprintln!("toggle  @ {:?}", Instant::now());
+
+        if *TOGGLE {
+            cx.resources.GPIOA.bsrr.write(|w| w.bs5().set_bit());
+        } else {
+            cx.resources.GPIOA.bsrr.write(|w| w.br5().set_bit());
+        }
+
+        *TOGGLE = !*TOGGLE;
+        cx.schedule.toggle(cx.scheduled + OFFSET.cycles()).unwrap();
+    }
+
+    extern "C" {
+        fn EXTI0();
+    }
+};
+
+// 1. In this example you will use RTT.
+//
+//    > cargo run --example rtic_bare7
+//
+//    Now look at the documentation for `embedded_hal::digital::v2::OutputPin`.
+//    (You created documentation for your dependencies in previous exercise
+//    so you can just search (press `S`) for `OutputPin`).
+//
+//    You see that the OutputPin trait defines `set_low`/`set_high` functions.
+//    Your task is to alter the code to use the `set_low`/`set_high` API.
+//
+//    HINTS:
+//    - A GPIOx peripheral can be `split` into individual PINs Px0..Px15).
+//    - A Pxy, can be turned into an `Output` by `into_push_pull_output`.
+//    - You may optionally set other pin properties as well (such as `speed`).
+//    - An `Output` pin provides `set_low`/`set_high`
+//      (and implements the `OutputPin` trait in embedded-hal).
+//
+//    Comment your code to explain the steps taken.
+//
+//    Confirm that your implementation correctly toggles the LED as in
+//    previous exercise.
+//
+//    Commit your code (bare7_1)
+//
+// 2. Optional
+//
+//    Use the `toggle` function instead to further simply your code.
+//
+//    Notice:
+//    The `ToggleableOutputPin` abstraction requires `embedded-hal`
+//    to compiled with the `unproven` feature.
+//
+//    The `embedded-hal` traits is mostly used to write drivers
+//    that is hardware agnostic (and thus cross platform).
+//
+//    However:
+//    In our case we can use `toggle` directly as implemented by the `stm32f4xx-hal`.
+//
+//    Confirm that your implementation correctly toggles the LED.
+//
+//    Which one do you prefer and why (what problem does it solve)?
+//
+//    ** your answer here **
+//
+//    Commit your answer (bare7_2)
+//
+// 3. Discussion
+//
+//    In this exercise you have learned more on navigating the generated documentation
+//    and to use abstractions to simplify and generalize your code.