Allow other image file names through cli args, increase ram size, update readme

README.md

@@ -8,12 +8,17 @@ potentially more. No plans for RV32I or RV32/64E.
 Currently, the emulator is nowhere near complete,
 its not even at rv64i, but it does work for a subset of it.
 
-The emulator will load a raw binary image from the file `./img` into RAM,
+The emulator will load a raw binary image from a file specified as a CLI argument into RAM,
-which starts at 0x80000000 and is currently 1MiB,
+which starts at 0x80000000 and is currently 16MiB,
 and start execution at the start of the image/ram.
 
 There is also a debug out page starting at `0x00000000`-`0x00001000`.
 Anything written to it will be logged out in hex.
 
-Currently there is no input, altho i might get around to making
+There is also a UART at `0x00001000`-`0x00002000`, the interface is quite simple:
-an early UART kinda soon.
+- byte `0`: Data. When written, writes out the character
+  When read, reads a character from the buffer, or 0 if empty.
+- byte `1`: Status. Read-only. Least significant bit is `TX_READY` and indicates whether
+  the UART is ready to be written to. Currently always 1.
+  Next least significant is `RX_READY`, indicates whether the read buffer
+  has any data to read.

src/main.rs

@@ -5,6 +5,7 @@
 // See LICENSE file in the project root for full license text.
 
 use std::{
+    env,
     error::Error,
     fs::File,
     io::{self, Read},
@@ -41,9 +42,16 @@ fn read_file_to_buffer(path: &str, buffer: &mut [u8]) -> io::Result<usize> {
 }
 
 fn main() -> Result<(), Box<dyn Error>> {
-    let mut ram = Ram::try_new(1024 * 1024 / 4096)?;
+    let mut ram = Ram::try_new(16 * 1024 * 1024 / 4096)?;
     let buf = ram.buf_mut();
-    read_file_to_buffer("./img", buf)?;
+
+    let args: Vec<String> = env::args().collect();
+
+    if args.len() != 2 {
+        eprintln!("USAGE: trve <ram_image>")
+    }
+
+    read_file_to_buffer(&args[1], buf)?;
 
     let uart = BasicUart::new();
     let uart = uart.spawn_poller(Duration::from_millis(10));