firmware: add UART

firmware/Cargo.toml

@@ -9,3 +9,6 @@ edition = "2021"
 riscv-rt = "0.11.0"
 panic-halt = "0.2.0"
 embedded-hal = "0.2.7"
+
+[profile.release]
+debug = true

firmware/memory.x

@@ -1,7 +1,7 @@
 MEMORY
 {
-  RAM : ORIGIN = 0x01001000, LENGTH = 4K
-  FLASH : ORIGIN = 0x01000000, LENGTH = 4K
+  RAM : ORIGIN = 0x01002000, LENGTH = 4K
+  FLASH : ORIGIN = 0x01000000, LENGTH = 8K
 }
 
 REGION_ALIAS("REGION_TEXT", FLASH);

firmware/src/eth.rs

@@ -1,6 +1,6 @@
 //! Quick and hacky ethernet thing to test
 
-const LITEETH_BASE: u32 = 0x0200_0000;
+const LITEETH_BASE: u32 = 0x0300_0000;
 
 const ETHMAC_SRAM_WRITER_EV_PENDING: u32 = LITEETH_BASE + 0x810;
 const ETHMAC_SRAM_WRITER_EV_ENABLE: u32 = LITEETH_BASE + 0x814;

firmware/src/main.rs

@@ -4,12 +4,14 @@
 extern crate panic_halt;
 
 use core::{arch::asm, ptr::{write, read}};
+use core::fmt::Write;
 
 use embedded_hal::prelude::_embedded_hal_blocking_i2c_Write;
 use riscv_rt::entry;
 
 mod eth;
 mod i2c;
+mod uart;
 
 // use `main` as the entry point of this application
 // `main` is not allowed to return
@@ -26,12 +28,15 @@ fn main() -> ! {
     //};
     let blink_period = 10_000_000u32;
 
-    let mut i2c = i2c::AmlibI2c::new(0x01003000);
-    let data = [0u8, 2u8];
-    i2c.write(0xAA, &data).unwrap();
+    //let mut i2c = i2c::AmlibI2c::new(0x0200_0000);
+    //let data = [0u8, 2u8];
+    //i2c.write(0xAA, &data).unwrap();
+
+    let mut uart = uart::AmlibUart::new(0x0200_0040);
 
     loop {
         //eth::tranmsit();
+        uart.write_str("Hello world!\r\n");
         write_led(0);
         busy_wait(blink_period);
         write_led(1);
@@ -48,7 +53,7 @@ fn busy_wait(num_nops: u32) {
 }
 
 fn write_led(val: u32) {
-    unsafe { write_reg(0x0100200, val); }
+    unsafe { write_reg(0x01003000, val); }
 }
 
 unsafe fn write_reg<T>(addr: u32, value: T) {

firmware/src/uart.rs

@@ -0,0 +1,75 @@
+//! Quick and dirty uart driver
+
+/// TODO repr(C) a register bank, and add instances
+/// 
+use core::ptr::{read_volatile, write_volatile};
+use core::fmt::{Write};
+
+// TODO these offsets may be wrong. I'm still unsure about CSR semantics
+const REG_DIVISOR_OFFSET: u32 = 0;
+const REG_SR_OFFSET: u32 = 2;
+const REG_DR_OFFSET: u32 = 3;
+
+pub const FLAG_SR_TX_FULL: u8 = (1 << 0);
+pub const FLAG_SR_TX_EMPTY: u8 = (1 << 1);
+pub const FLAG_SR_RX_FULL: u8 = (1 << 2);
+pub const FLAG_SR_RX_EMPTY: u8 = (1 << 3);
+
+pub enum Error {
+    TxFull,
+    RxEmpty,
+}
+
+pub struct AmlibUart {
+    base_addr: u32,
+}
+
+impl AmlibUart {
+    pub fn new(base_addr: u32) -> Self {
+        Self {
+            base_addr,
+        }
+    }
+
+
+    pub fn read_status(&mut self) -> u8 {
+        unsafe {
+            read_volatile((self.base_addr + REG_SR_OFFSET) as *const u8)
+        }
+    }
+
+    pub fn try_get_char(&mut self) -> Result<u8, Error> {
+        if self.read_status() & FLAG_SR_RX_EMPTY != 0 {
+            return Err(Error::RxEmpty);
+        }
+
+        unsafe {
+            Ok(read_volatile((self.base_addr + REG_DR_OFFSET) as *const u8))
+        }
+    }
+
+    pub fn try_put_char(&mut self, c: u8) -> Result<(), Error> {
+        if self.read_status() & FLAG_SR_TX_FULL != 0 {
+            return Err(Error::TxFull);
+        }
+
+        unsafe {
+            write_volatile((self.base_addr + REG_DR_OFFSET) as *mut u8, c);
+        }
+        Ok(())
+    }
+
+}
+
+// Blocking implementation of write
+impl Write for AmlibUart {
+    fn write_str(&mut self, s: &str) -> core::fmt::Result {
+        for b in s.as_bytes() {
+            // It's okay to loop on this because we'll always clear the buffer
+            while let Err(Error::TxFull) = self.try_put_char(*b) {}
+            //self.try_put_char(*b);
+        }
+
+        Ok(())
+    }
+}