diff --git a/.vscode/launch.json b/.vscode/launch.json
index b61b652ebe740398cfaf97c44b2e864c70208fa9..df1f5da4233c32f202ce0528ab3bf8d004983751 100644
--- a/.vscode/launch.json
+++ b/.vscode/launch.json
@@ -226,6 +226,64 @@
],
"cwd": "${workspaceRoot}"
},
+ {
+ "type": "cortex-debug",
+ "request": "launch",
+ "servertype": "openocd",
+ "name": "bare2 (debug)",
+ "preLaunchTask": "cargo build --example bare2",
+ "executable": "./target/thumbv7em-none-eabihf/debug/examples/bare2",
+ "postLaunchCommands": [
+ "monitor arm semihosting enable"
+ ],
+ "swoConfig": {
+ "enabled": true,
+ "cpuFrequency": 16000000,
+ "swoFrequency": 2000000,
+ "source": "probe",
+ "decoders": [
+ {
+ "type": "console",
+ "label": "ITM",
+ "port": 0
+ }
+ ]
+ },
+ "configFiles": [
+ "interface/stlink.cfg",
+ "target/stm32f4x.cfg"
+ ],
+ "cwd": "${workspaceRoot}"
+ },
+ {
+ "type": "cortex-debug",
+ "request": "launch",
+ "servertype": "openocd",
+ "name": "bare2 (release)",
+ "preLaunchTask": "cargo build --example bare2",
+ "executable": "./target/thumbv7em-none-eabihf/release/examples/bare2",
+ "postLaunchCommands": [
+ "monitor arm semihosting enable"
+ ],
+ "swoConfig": {
+ "enabled": true,
+ "cpuFrequency": 16000000,
+ "swoFrequency": 2000000,
+ "source": "probe",
+ "decoders": [
+ {
+ "type": "console",
+ "label": "ITM",
+ "port": 0
+ }
+ ]
+ },
+ "configFiles": [
+ "interface/stlink.cfg",
+ "target/stm32f4x.cfg"
+ ],
+ "cwd": "${workspaceRoot}"
+ },
{
"type": "cortex-debug",
"request": "launch",
diff --git a/.vscode/tasks.json b/.vscode/tasks.json
index d0ca15ac546b33228ab89ae5092ecab195ade166..6bd84bc5bb4d224239ac82f575acfb899227221e 100644
--- a/.vscode/tasks.json
+++ b/.vscode/tasks.json
@@ -111,5 +111,29 @@
"isDefault": true
}
},
+ {
+ "type": "shell",
+ "label": "cargo build --example bare2",
+ "command": "cargo build --example bare2",
+ "problemMatcher": [
+ "$rustc"
+ ],
+ "group": {
+ "kind": "build",
+ "isDefault": true
+ }
+ },
+ {
+ "type": "shell",
+ "label": "cargo build --example bare2 --release",
+ "command": "cargo build --example bare2 --release",
+ "problemMatcher": [
+ "$rustc"
+ ],
+ "group": {
+ "kind": "build",
+ "isDefault": true
+ }
+ }
]
}
\ No newline at end of file
diff --git a/examples/bare1.rs b/examples/bare1.rs
new file mode 100644
index 0000000000000000000000000000000000000000..4a10eced59853290b20228d905f2793f1ee0bbcd
--- /dev/null
+++ b/examples/bare1.rs
@@ -0,0 +1,161 @@
+//! bare1.rs
+//!
+//! Tracing and assembly code
+//!
+//! What it covers
+//! - tracing over semihosting and ITM
+//! - assembly calls and inline assembly
+//! - more on arithmetics
+//! ---
+
+#![no_main]
+#![no_std]
+
+extern crate panic_halt;
+
+use cortex_m::{iprintln, Peripherals};
+use cortex_m_rt::entry;
+use cortex_m_semihosting::hprintln;
+
+#[entry]
+fn main() -> ! {
+ let mut p = Peripherals::take().unwrap();
+ let stim = &mut p.ITM.stim[0];
+
+ let mut x = 27;
+ iprintln!(stim, "x = {:?}", x);
+ hprintln!("x = {:?}", x).unwrap();
+ loop {
+ x += 1;
+ cortex_m::asm::nop();
+ cortex_m::asm::bkpt();
+ x -= 1;
+ }
+}
+
+// 0. Setup
+// For this example we will use the `nightly` compiler
+// to get true inline assembly.
+//
+// > rustup override set nightly
+//
+// You may need/want to install addititonal components also),
+// to that end look at the install section in the README.md.
+// If you change toolchain, exit and re-start `vscode`.
+//
+// 1. Build and run the application
+// Look at the `hello.rs` and `itm.rs` examples to setup the tracing.
+//
+// When debugging the application it should get stuck in the
+// loop, (press pause/suspend to verify this).
+// what is the output in the ITM console
+//
+// ** your answer here **
+//
+// What is the output in the semihosting (openocd) console
+// ** your answer here **
+//
+// commit your answers (bare1_1)
+//
+// 2. Inspecting the generated assembly code
+// If in `vcsode` the gdb console in DEBUG CONSOLE
+// What is the output of:
+// (gdb) disassemble
+//
+// ** your answer here **
+//
+// commit your answers (bare1_2)
+//
+// 3. Now remove the comment for `cortex_m::asm::nop()`.
+// Rebuild and debug, pause the program.
+// What is the output of:
+// (gdb) disassemble
+//
+// ** your answer here **
+//
+// commit your answers (bare1_3)
+//
+// 4. Now remove the comment for `cortex_m::asm::bkpt()`
+// Rebuild and debug, let the program run until it halts.
+// What is the output of:
+// (gdb) disassemble
+//
+// ** your answer here **
+//
+// commit your answers (bare1_4)
+//
+// 5. Release mode (optimized builds).
+// Rebuild `bare1.rs` in release (optimized mode).
+// Compare the generated assembly for the loop
+// between the dev (unoptimized) and release (optimized) build.
+//
+// ** your answer here **
+//
+// commit your answers (bare1_5)
+//
+// Tips: The optimized build should have some 8 instructions
+// while the debug (dev) build should have > 20 instructions
+// (both counting the inner loop only). The debug build
+// should have additional code that call panic if the additon
+// wraps (and in such case call panic).
+//
+// Discussion:
+// In release (optimized) mode the addition is unchecked,
+// so there is a semantic difference here in between
+// the dev and release modes. This is motivited by:
+// 1) efficiency, unchecked is faster
+// 2) convenience, it would be inconvenient to explicitly use
+// wrapping arithmetics, and wrapping is what the programmer
+// typically would expect in any case. So the check
+// in dev/debug mode is just there for some extra safety
+// if your intention is NON-wrapping arithmetics.
+//
+// 6. *Optional
+// You can pass additional flags to the Rust `rustc` compiler.
+//
+// `-Z force-overflow-checks=off`
+//
+// Under this flag, code is never generated for oveflow checking.
+// You can enable this flag (uncomment the corresponding flag in
+// the `.cargo/config` file.)
+//
+// What is now the disassembly of the loop:
+//
+// ** your answer here **
+//
+// commit your answers (bare1_6)
+//
+// Now restore the `.cargo/config` to its original state.
+//
+// 7. *Optional
+// There is another way to conveniently use wrapping arithmetics
+// without passing flags to the compiler.
+//
+// https://doc.rust-lang.org/std/num/struct.Wrapping.html
+//
+// Rewrite the code using this approach.
+//
+// What is now the disassembly of the code in dev mode?
+//
+// ** your answer here **
+//
+// What is now the disassembly of the code in release mode?
+//
+// ** your answer here **
+//
+// commit your answers (bare1_7)
+//
+// Final discussion:
+//
+// Embedded code typically is performance sensitve, hence
+// it is important to understand how code is generated
+// to achieve efficient implementations.
+//
+// Moreover, arithmetics are key to processing of data,
+// so its important that we are in control over the
+// computations. E.g. comupting checksums, hashes, cryptos etc.
+// all require precise control over wrapping vs. overflow behaviour.
+//
+// If you write a library depending on wrapping arithmetics
+// do NOT rely on a compiler flag. (The end user might compile
+// it without this flag enabled, and thus get erronous results.)