Working dual vga/serial console.

Author: thejpster

Cargo.toml

@@ -21,3 +21,6 @@ opt-level = "s"
 
 [dependencies.neotron-common-bios]
 path = "./common"
+
+[dependencies.r0]
+version = "1.0"

README.md

@@ -7,7 +7,8 @@ This is the Neotron OS. It will run on any system which can execute ARM Thumb v7
 This OS is a work in progress. We intend to support:
 
 * [x] Calling BIOS APIs
-* [ ] Text mode console (on both text and bitmap displays)
+* [x] Text mode VGA console
+* [x] Serial console
 * [ ] Starting a command-line shell application
 * [ ] Executing applications from RAM
 * [ ] MBR/FAT32 formatted block devices with standard open/close/read/write file semantics
@@ -21,7 +22,11 @@ This OS is a work in progress. We intend to support:
 Your board will need an appropriate Neotron BIOS installed, and you need to have OpenOCD running for your particular board. You also need to set the linker 
 arguments so you link the binary to suit the memory available on your system.
 
-### Build Instructions for the Neotron 340ST
+### Build Instructions for 256K RAM systems
+
+Systems which reserve the second 512 KiB of Flash and first 256 KiB of SRAM
+for the OS can use this linker script. These systems include the Neotron
+340ST.
 
 ```
 $ git clone https://github.com/neotron-compute/Neotron-OS.git
@@ -30,7 +35,10 @@ $ git submodule update --init
 $ RUSTFLAGS="-C link-arg=-Tneotron-os-256k.ld" cargo run --release
 ```
 
-### Build Instructions for the Neotron 32
+### Build Instructions for 32K RAM systems
+
+Systems which reserve the second 128 KiB of Flash and first 26 KiB of SRAM for
+the OS can use this linker script. These systems include the Neotron 32.
 
 ```
 $ git clone https://github.com/neotron-compute/Neotron-OS.git
@@ -45,7 +53,7 @@ TODO: Think of a better way of setting the memory limits for a particular OS bui
 
 ### Unreleased Changes ([Source](https://github.com/neotron-compute/Neotron-OS/tree/master))
 
-* Basic UART hello on start-up on the Neotron 32 and Neotron 340ST
+* Basic `println!` to the text buffer.
 
 ## Licence
 

common

@@ -18,7 +18,6 @@ monitor arm semihosting enable
 # monitor itm port 0 on
 
 load
-step
-continue
-
+monitor reset halt
+stepi
 

gdb.cfg

@@ -1,21 +1,70 @@
 //! # The Neotron Operating System
 //!
 //! This OS is intended to be loaded by a Neotron BIOS.
+//!
+//! Copyright (c) The Neotron Developers, 2020
+//!
+//! Licence: GPL v3 or higher (see ../LICENCE.md)
+
 #![no_std]
 #![no_main]
 
+// Imports
 use core::fmt::Write;
-use neotron_common_bios as common;
+use neotron_common_bios as bios;
 
+// ===========================================================================
+// Global Variables
+// ===========================================================================
+
+/// This tells the BIOS how to start the OS. This must be the first four bytes
+/// of our portion of Flash.
 #[link_section = ".entry_point"]
-#[no_mangle]
 #[used]
-pub static ENTRY_POINT: extern "C" fn(&'static common::Api) -> ! = entry_point;
+pub static ENTRY_POINT_ADDR: extern "C" fn(&'static bios::Api) -> ! = main;
 
 /// The OS version string
-static OS_VERSION: &str = concat!("Neotron OS, version ", env!("CARGO_PKG_VERSION"), "\0");
+const OS_VERSION: &str = concat!("Neotron OS, version ", env!("CARGO_PKG_VERSION"), "-2");
+
+/// We store the API object supplied by the BIOS here
+static mut API: Option<&'static bios::Api> = None;
 
-static mut API: Option<&'static common::Api> = None;
+/// We store our VGA console here.
+static mut VGA_CONSOLE: Option<VgaConsole> = None;
+
+/// We store our VGA console here.
+static mut SERIAL_CONSOLE: Option<SerialConsole> = None;
+
+// ===========================================================================
+// Macros
+// ===========================================================================
+
+/// Prints to the screen
+#[macro_export]
+macro_rules! print {
+    ($($arg:tt)*) => {
+        if let Some(ref mut console) = unsafe { &mut VGA_CONSOLE } {
+            write!(console, $($arg)*).unwrap();
+        }
+        if let Some(ref mut console) = unsafe { &mut SERIAL_CONSOLE } {
+            write!(console, $($arg)*).unwrap();
+        }
+    };
+}
+
+/// Prints to the screen and puts a new-line on the end
+#[macro_export]
+macro_rules! println {
+    () => (print!("\n"));
+    ($($arg:tt)*) => {
+        print!($($arg)*);
+        print!("\n");
+    };
+}
+
+// ===========================================================================
+// Local types
+// ===========================================================================
 
 #[derive(Debug)]
 struct VgaConsole {
@@ -26,21 +75,6 @@ struct VgaConsole {
     col: u8,
 }
 
-struct SerialConsole;
-
-impl core::fmt::Write for SerialConsole {
-    fn write_str(&mut self, data: &str) -> core::fmt::Result {
-        if let Some(api) = unsafe { API } {
-            let _res = (api.serial_write)(
-                0,
-                common::ApiByteSlice::new(data.as_bytes()),
-                common::Option::None,
-            );
-        }
-        Ok(())
-    }
-}
-
 impl VgaConsole {
     const DEFAULT_ATTR: u8 = (2 << 3) | (1 << 0);
 
@@ -130,39 +164,145 @@ impl core::fmt::Write for VgaConsole {
     }
 }
 
-#[no_mangle]
-extern "C" fn entry_point(api: &'static common::Api) -> ! {
+/// Represents the serial port we can use as a text input/output device.
+struct SerialConsole(u8);
+
+impl core::fmt::Write for SerialConsole {
+    fn write_str(&mut self, data: &str) -> core::fmt::Result {
+        if let Some(api) = unsafe { API } {
+            (api.serial_write)(
+                // Which port
+                self.0,
+                // Data
+                bios::ApiByteSlice::new(data.as_bytes()),
+                // No timeout
+                bios::Option::None,
+            )
+            .unwrap();
+        }
+        Ok(())
+    }
+}
+
+// ===========================================================================
+// Private functions
+// ===========================================================================
+
+/// Initialise our global variables - the BIOS will not have done this for us
+/// (as it doesn't know where they are).
+unsafe fn start_up_init() {
+    extern "C" {
+
+        // These symbols come from `link.x`
+        static mut __sbss: u32;
+        static mut __ebss: u32;
+
+        static mut __sdata: u32;
+        static mut __edata: u32;
+        static __sidata: u32;
+    }
+
+    r0::zero_bss(&mut __sbss, &mut __ebss);
+    r0::init_data(&mut __sdata, &mut __edata, &__sidata);
+}
+
+struct Config {
+    vga_console: bool,
+    serial_console: bool,
+}
+
+impl Config {
+    /// Create a new default Config object
+    ///
+    /// TODO: We should load from EEPROM / RTC SRAM here.
+    fn new() -> Config {
+        Config {
+            vga_console: true,
+            serial_console: true,
+        }
+    }
+
+    /// Should this system use the VGA console?
+    fn has_vga_console(&self) -> bool {
+        self.vga_console
+    }
+
+    /// Should this system use the UART console?
+    fn has_serial_console(&self) -> Option<(u8, bios::serial::Config)> {
+        if self.serial_console {
+            Some((
+                0,
+                bios::serial::Config {
+                    data_rate_bps: 115200,
+                    data_bits: bios::serial::DataBits::Eight,
+                    stop_bits: bios::serial::StopBits::One,
+                    parity: bios::serial::Parity::None,
+                    handshaking: bios::serial::Handshaking::None,
+                },
+            ))
+        } else {
+            None
+        }
+    }
+}
+
+// ===========================================================================
+// Public functions / impl for public types
+// ===========================================================================
+
+/// This is the function the BIOS calls. This is because we store the address
+/// of this function in the ENTRY_POINT_ADDR variable.
+extern "C" fn main(api: &'static bios::Api) -> ! {
     unsafe {
+        start_up_init();
         API = Some(api);
     }
-    let mut addr: *mut u8 = core::ptr::null_mut();
-    let mut width = 0;
-    let mut height = 0;
-    (api.video_memory_info_get)(&mut addr, &mut width, &mut height);
-    let mut vga = VgaConsole {
-        addr,
-        width,
-        height,
-        row: 0,
-        col: 0,
-    };
-    vga.find_start_row();
-    writeln!(vga, "{}", OS_VERSION).unwrap();
-    writeln!(vga, "BIOS Version: {}", (api.bios_version_get)()).unwrap();
-    writeln!(vga, "BIOS API Version: {}", (api.api_version_get)()).unwrap();
-    loop {
-        for _ in 0..1_000_000 {
-            let _ = (api.api_version_get)();
+
+    let config = Config::new();
+
+    if config.has_vga_console() {
+        let mut addr: *mut u8 = core::ptr::null_mut();
+        let mut width = 0;
+        let mut height = 0;
+        (api.video_memory_info_get)(&mut addr, &mut width, &mut height);
+        if addr != core::ptr::null_mut() {
+            let mut vga = VgaConsole {
+                addr,
+                width,
+                height,
+                row: 0,
+                col: 0,
+            };
+            vga.find_start_row();
+            unsafe {
+                VGA_CONSOLE = Some(vga);
+            }
+            println!("Configured VGA console");
         }
-        writeln!(vga, "tick...").unwrap();
     }
+
+    if let Some((idx, serial_config)) = config.has_serial_console() {
+        let _ignored = (api.serial_configure)(idx, serial_config);
+        unsafe { SERIAL_CONSOLE = Some(SerialConsole(idx)) };
+        println!("Configured Serial console on Serial {}", idx);
+    }
+
+    // Now we can call println!
+    println!("Welcome to {}!", OS_VERSION);
+    panic!("Testing a panic...");
 }
 
+/// Called when we have a panic.
 #[inline(never)]
 #[panic_handler]
-fn panic(_info: &core::panic::PanicInfo) -> ! {
+fn panic(info: &core::panic::PanicInfo) -> ! {
+    println!("PANIC!\n{:#?}", info);
     use core::sync::atomic::{self, Ordering};
     loop {
         atomic::compiler_fence(Ordering::SeqCst);
     }
 }
+
+// ===========================================================================
+// End of file
+// ===========================================================================