Adds a simple UART example

Provides a simple UART example so that we can test out UART on the nRF52840 and nRF9160

examples/hello-world/Cargo.toml

@@ -0,0 +1,30 @@
+[package]
+name = "hello-world"
+version = "0.1.0"
+authors = ["Christopher Hunt"]
+edition = "2018"
+publish = false
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+cortex-m = "0.6.2"
+cortex-m-rt = "0.6.12"
+
+[dependencies.embedded-hal]
+version = "0.2.3"
+features = ["unproven"]
+
+[dependencies.nrf9160-hal]
+features = ["rt"]
+path = "../../nrf9160-hal"
+optional = true
+
+[dependencies.nrf52840-hal]
+features = ["rt"]
+path = "../../nrf52840-hal"
+optional = true
+
+[features]
+9160 = ["nrf9160-hal"]
+52840 = ["nrf52840-hal"]

examples/hello-world/Embed.toml

@@ -0,0 +1,63 @@
+[default.probe]
+# USB vendor ID
+# usb_vid = "1337"
+# USB product ID
+# usb_pid = "1337"
+# Serial number
+# serial = "12345678"
+# The protocol to be used for communicating with the target.
+protocol = "Swd"
+# The speed in kHz of the data link to the target.
+# speed = 1337
+
+[default.flashing]
+# Whether or not the target should be flashed.
+enabled = true
+# Whether or not the target should be halted after reset.
+# DEPRECATED, moved to reset section
+halt_afterwards = false
+# Whether or not bytes erased but not rewritten with data from the ELF
+# should be restored with their contents before erasing.
+restore_unwritten_bytes = false
+# The path where an SVG of the assembled flash layout should be written to.
+# flash_layout_output_path = "out.svg"
+
+[default.reset]
+# Whether or not the target should be reset.
+# When flashing is enabled as well, the target will be reset after flashing.
+enabled = true
+# Whether or not the target should be halted after reset.
+halt_afterwards = false
+
+[default.general]
+# The chip name of the chip to be debugged.
+chip = "nRF52840_xxAA"
+# A list of chip descriptions to be loaded during runtime.
+chip_descriptions = []
+# The default log level to be used. Possible values are one of:
+#   "OFF", "ERROR", "WARN", "INFO", "DEBUG", "TRACE" 
+log_level = "WARN"
+
+[default.rtt]
+# Whether or not an RTTUI should be opened after flashing.
+# This is exclusive and cannot be used with GDB at the moment.
+enabled = false
+# A list of channel associations to be displayed. If left empty, all channels are displayed.
+channels = [
+    # { up = 0, down = 0, name = "name", format = "String" }
+]
+# The duration in ms for which the logger should retry to attach to RTT.
+timeout = 3000
+# Whether timestamps in the RTTUI are enabled
+show_timestamps = true
+# Whether to save rtt history buffer on exit.
+log_enabled = false
+# Where to save rtt history buffer relative to manifest path.
+log_path = "./logs"
+
+[default.gdb]
+# Whether or not a GDB server should be opened after flashing.
+# This is exclusive and cannot be used with RTT at the moment.
+enabled = false
+# The connection string in host:port format wher the GDB server will open a socket.
+# gdb_connection_string

examples/hello-world/build.rs

@@ -0,0 +1,36 @@
+//! 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.
+
+fn main() {
+    // We only need the memory.x file for the nRF9160 as our program
+    // must then reside in a location where unsecure programs need to be.
+    #[cfg(feature = "9160")]
+    {
+        use std::env;
+        use std::fs::File;
+        use std::io::Write;
+        use std::path::PathBuf;
+
+        // 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");
+    }
+}

examples/hello-world/memory.x

@@ -0,0 +1,32 @@
+MEMORY
+{
+  /* NOTE 1 K = 1 KiBi = 1024 bytes */
+  FLASH : ORIGIN = 0x00050000, LENGTH = 768K
+  RAM : ORIGIN = 0x20020000, LENGTH = 128K
+}
+
+/* This is where the call stack will be allocated. */
+/* The stack is of the full descending type. */
+/* You may want to use this variable to locate the call stack and static
+   variables in different memory regions. Below is shown the default value */
+/* _stack_start = ORIGIN(RAM) + LENGTH(RAM); */
+
+/* You can use this symbol to customize the location of the .text section */
+/* If omitted the .text section will be placed right after the .vector_table
+   section */
+/* This is required only on microcontrollers that store some configuration right
+   after the vector table */
+/* _stext = ORIGIN(FLASH) + 0x400; */
+
+/* Example of putting non-initialized variables into custom RAM locations. */
+/* This assumes you have defined a region RAM2 above, and in the Rust
+   sources added the attribute `#[link_section = ".ram2bss"]` to the data
+   you want to place there. */
+/* Note that the section will not be zero-initialized by the runtime! */
+/* SECTIONS {
+     .ram2bss (NOLOAD) : ALIGN(4) {
+       *(.ram2bss);
+       . = ALIGN(4);
+     } > RAM2
+   } INSERT AFTER .bss;
+*/

examples/hello-world/src/main.rs

@@ -0,0 +1,64 @@
+#![no_std]
+#![no_main]
+
+// Simple UART example
+
+#[cfg(feature = "52840")]
+use nrf52840_hal as hal;
+#[cfg(feature = "9160")]
+use nrf9160_hal as hal;
+
+use core::fmt::Write;
+use hal::{gpio, uarte, uarte::Uarte};
+
+#[cortex_m_rt::entry]
+fn main() -> ! {
+    let p = hal::pac::Peripherals::take().unwrap();
+
+    #[cfg(feature = "52840")]
+    let (uart0, cdc_pins) = {
+        let p0 = gpio::p0::Parts::new(p.P0);
+        (
+            p.UARTE0,
+            uarte::Pins {
+                txd: p0.p0_06.into_push_pull_output(gpio::Level::High).degrade(),
+                rxd: p0.p0_08.into_floating_input().degrade(),
+                cts: Some(p0.p0_07.into_floating_input().degrade()),
+                rts: Some(p0.p0_05.into_push_pull_output(gpio::Level::High).degrade()),
+            },
+        )
+    };
+    #[cfg(feature = "9160")]
+    let (uart0, cdc_pins) = {
+        let p0 = gpio::p0::Parts::new(p.P0_NS);
+        (
+            p.UARTE0_NS,
+            uarte::Pins {
+                txd: p0.p0_29.into_push_pull_output(gpio::Level::High).degrade(),
+                rxd: p0.p0_28.into_floating_input().degrade(),
+                cts: Some(p0.p0_26.into_floating_input().degrade()),
+                rts: Some(p0.p0_27.into_push_pull_output(gpio::Level::High).degrade()),
+            },
+        )
+    };
+
+    let mut uarte = Uarte::new(
+        uart0,
+        cdc_pins,
+        uarte::Parity::EXCLUDED,
+        uarte::Baudrate::BAUD115200,
+    );
+
+    write!(uarte, "Hello, World!\r\n").unwrap();
+
+    loop {
+        cortex_m::asm::wfi();
+    }
+}
+
+#[panic_handler] // panicking behavior
+fn panic(_: &core::panic::PanicInfo) -> ! {
+    loop {
+        cortex_m::asm::bkpt();
+    }
+}

xtask/src/lib.rs

@@ -18,6 +18,7 @@ pub static EXAMPLES: &[(&str, &[&str])] = &[
         "ecb-demo",
         &["51", "52810", "52811", "52832", "52833", "52840"],
     ),
+    ("hello-world", &["52840"]),
     ("gpiote-demo", &[]),
     ("i2s-controller-demo", &[]),
     ("i2s-peripheral-demo", &[]),