Basic hello world example that runs on the metro m0 express

.cargo/config

@@ -0,0 +1,13 @@
+# samd21 is a Cortex-M0 and thus thumbv6m
+
+[build]
+target = "thumbv6m-none-eabi"
+
+[target.thumbv6m-none-eabi]
+runner = 'arm-none-eabi-gdb'
+rustflags = [
+  "-C", "link-arg=-Tlink.x",
+  "-C", "linker=arm-none-eabi-ld",
+  "-Z", "linker-flavor=ld",
+  "-Z", "thinlto=no",
+]

.gdbinit

@@ -0,0 +1,18 @@
+# print demangled symbols by default
+set print asm-demangle on
+
+# JLink
+target extended-remote :2331
+monitor flash breakpoints 1
+# allow hprints to show up in gdb
+monitor semihosting enable
+monitor semihosting IOClient 3
+
+monitor reset
+load
+
+# OpenOCD
+#target extended-remote :3333
+#monitor arm semihosting enable
+#load
+#step

.gitignore

@@ -3,3 +3,4 @@
 [._]*.sw[a-p]
 /target
 Cargo.lock
+/.gdb_history

Cargo.toml

@@ -1,2 +1,28 @@
 [workspace]
 members = ["atsamd21g18a"]
+
+[package]
+name = "samd21"
+version = "0.0.0"
+
+[dependencies]
+cortex-m = "0.4.3"
+cortex-m-semihosting = "0.2.0"
+
+[dependencies.cortex-m-rt]
+version = "0.3.13"
+features = ["abort-on-panic"]
+
+[dependencies.atsamd21g18a]
+path = "atsamd21g18a"
+features = ["rt"]
+
+# disable both incremental compilation and parallel codegen to
+# reduce the chances of running into rust-lang/rust#47074
+[profile.dev]
+codegen-units = 1
+incremental = false
+
+[profile.release]
+debug = true
+lto = true

Xargo.toml

@@ -0,0 +1,10 @@
+[dependencies.core]
+stage = 0
+
+# [dependencies.alloc] # Uncomment for the alloc example.
+# stage = 0
+
+[dependencies.compiler_builtins]
+features = ["mem"]
+stage = 1
+

atsamd21g18a/Cargo.toml

@@ -8,12 +8,12 @@ license = "MIT OR Apache-2.0"
 
 [dependencies]
 bare-metal = "0.1.1"
-cortex-m = "0.4.0"
+cortex-m = "0.4.3"
 vcell = "0.1.0"
 
 [dependencies.cortex-m-rt]
 optional = true
-version = "0.3.0"
+version = "0.3.13"
 
 [features]
 rt = ["cortex-m-rt"]

build.rs

@@ -0,0 +1,17 @@
+use std::env;
+use std::fs::File;
+use std::io::Write;
+use std::path::PathBuf;
+
+fn main() {
+    // Put the linker script somewhere the linker can find it
+    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());
+
+    println!("cargo:rerun-if-changed=build.rs");
+    println!("cargo:rerun-if-changed=memory.x");
+}

memory.x

@@ -0,0 +1,8 @@
+MEMORY
+{
+  // Leave 8k for the default bootloader on the Metro M0
+  FLASH (rx) : ORIGIN = 0x00000000 + 8K, LENGTH = 256K - 8K
+  RAM (xrw)  : ORIGIN = 0x20000000, LENGTH = 32K
+}
+_stack_start = ORIGIN(RAM) + LENGTH(RAM);
+

src/main.rs

@@ -0,0 +1,15 @@
+#![feature(used)]
+#![no_std]
+
+extern crate atsamd21g18a;
+extern crate cortex_m;
+extern crate cortex_m_rt;
+extern crate cortex_m_semihosting;
+
+use core::fmt::Write;
+use cortex_m_semihosting::hio;
+
+fn main() {
+    let mut stdout = hio::hstdout().unwrap();
+    writeln!(stdout, "Hello, world!").unwrap();
+}