Fix stack

lwcpu/src/lib.rs

@@ -18,12 +18,10 @@ const TEXT_DISPLAY_POINTER   : *mut u8  = (BASE_POINTER + TEXT_DISPLAY_OFFSET)
 const KEYBOARD_POINTER: *mut u32 = (BASE_POINTER + KEYBOARD_OFFSET) as *mut u32;
 const SCREEN_POINTER: *mut u32 = (BASE_POINTER + SCREEN_OFFSET) as *mut u32;
 
-
 pub struct Screen {}
 impl Screen {
     #[inline]
-    pub fn clear() {
-    }
+    pub fn clear() {}
     #[inline]
     pub fn turn_pixel_on(x: u8, y: u8) {
         unsafe {
@@ -57,6 +55,17 @@ impl TextDisplay {
         }
     }
 }
+impl core::fmt::Write for TextDisplay {
+    #[inline]
+    fn write_str(&mut self, s: &str) -> core::fmt::Result {
+        for ch in s.bytes() {
+            unsafe {
+                write_volatile(TEXT_DISPLAY_POINTER, ch);
+            }
+        }
+        return Ok(());
+    }
+}
 
 pub struct NumberDisplay {}
 impl NumberDisplay {

test/Cargo.toml

@@ -5,7 +5,7 @@ edition = "2021"
 
 [dependencies]
 riscv = "0.12.1"
-riscv-rt = "0.13.0"
+riscv-rt = { version = "0.13.0", features=["single-hart"] }
 lwcpu = { path = "../lwcpu" }
 
 # https://docs.rust-embedded.org/book/unsorted/speed-vs-size.html

test/Makefile

@@ -12,7 +12,7 @@ extract: build
 size: extract
 	cargo size --release -- -A
 
-disassemble: build
+disassemble: extract
 	riscv32-elf-objdump -Cd "target/riscv32i-unknown-none-elf/release/${NAME}" | less
 
 clean:

test/src/main.rs

@@ -1,8 +1,8 @@
 #![no_std]
 #![no_main]
 
-use core::panic::PanicInfo;
-use lwcpu::{self, NumberDisplay, Screen, TextDisplay};
+use core::{fmt::Write, panic::PanicInfo};
+use lwcpu::{NumberDisplay, Screen, TextDisplay};
 use riscv_rt::entry;
 
 #[panic_handler]
@@ -11,16 +11,15 @@ fn panic_handler(_info: &PanicInfo) -> ! {
     loop {}
 }
 
-const HELLO_WORLD: &[u8; 13] = b" Hello world!";
+const HELLO_WORLD: &str = " Hello world!";
 
 #[entry]
 fn main() -> ! {
+    let mut text = TextDisplay{};
     for i in 0..31 {
         Screen::set_line(i, 1 << i);
     }
     loop {
-        for ch in HELLO_WORLD {
-            TextDisplay::put_char(*ch);
-        }
+        let _ = text.write_str(HELLO_WORLD);
     }
 }