Add C and ASM examples.

Author: thejpster

samples/README.md

@@ -41,3 +41,11 @@ This application panics, printing a nice panic message.
 ## [`fault`](./fault)
 
 This application generates a Hard Fault.
+
+## [`asmhello`](./asmhello)
+
+A basic "Hello, world" but written in ARM assembly. It prints the string "Hello, world" to *standard output* and then exits with an exit code of 0.
+
+## [`chello`](../chello)
+
+A basic "Hello, world" but written in C. It prints the string "Hello, world" to *standard output* and then exits with an exit code of 0.

samples/asmhello/.gitignore

@@ -0,0 +1,2 @@
+*.elf
+*.o

samples/asmhello/asmhello.S

@@ -0,0 +1,35 @@
+.syntax unified
+.thumb
+.cpu cortex-m0plus
+.global app_entry
+.thumb_func
+
+.text
+.section ".text"
+
+// r0 will contain a pointer to the syscall table
+// the write function is the third entry (offset 8)
+// and takes the arguments r0=handle, r1=pointer, r2=length
+app_entry:
+    // Save registers
+    push {r0, r1, r2, lr}
+    // Fetch write function address
+    ldr r3, [r0, #8]
+    // Set up data length
+    movs r2, #13
+    // Set up file handle
+    movs r0, #1
+    // Set up data pointer
+    ldr r1, =message
+    // Call write function
+    blx r3
+    // Set return value
+    movs r0, #0
+    // Exit
+    pop {r1, r2, r3, pc}
+
+.data
+.section ".rodata"
+
+message:
+.ascii "Hello world!\n"

samples/asmhello/build.sh

@@ -0,0 +1,2 @@
+#!/bin/sh
+arm-none-eabi-gcc -mcpu=cortex-m0 -Wl,-T../neotron-cortex-m.ld -o asmhello.elf asmhello.S -nostdlib

samples/build.sh

@@ -24,6 +24,16 @@ cargo build
 echo "Building for ${TARGET}"
 cargo build --target ${TARGET} --release
 
+pushd chello
+./build.sh
+popd
+
+pushd asmhello
+./build.sh
+popd
+
 for program in panic hello fault input-test; do
     cp ./target/${TARGET}/release/${program} ./release/${program}.elf
 done
+cp ./asmhello/asmhello.elf ./release
+cp ./chello/chello.elf ./release

samples/chello/.gitignore

@@ -0,0 +1 @@
+*.elf

samples/chello/build.sh

@@ -0,0 +1,2 @@
+#!/bin/sh
+arm-none-eabi-gcc -Os -mcpu=cortex-m0 -Wl,-T../neotron-cortex-m.ld -o chello.elf chello.c -nostdlib

samples/chello/chello.c

@@ -0,0 +1,19 @@
+/**
+ * Basic C sample which runs on Neotron OS.
+ */
+
+#include "neotron.h"
+
+int app_entry(const NeotronApi *f)
+{
+    FfiByteSlice buffer = {
+        .data = "Hello, world",
+        .data_len = 12
+    };
+    Handle fd = {
+        // fd 1 is STDOUT
+        ._0 = 1
+    };
+    f->write(fd, buffer);
+    return 0;
+}