Implement UART write for raspi 3

src/bsp/rpi3/uart.rs

@@ -29,7 +29,7 @@ impl<'a> UartInner<'a> {
         
         self.flush();
         
-        // Stop UART
+        // Stop UART, see doc of CR register for the config process (P 185, doc BCM2835)
         self.memory_map.cr_uarten.read_and_write(0);
 
         // Flush the FIFOs
@@ -54,7 +54,8 @@ impl<'a> UartInner<'a> {
         self.memory_map.lcrh.write_without_read(lcrh_val);
 
         let cr_val = self.memory_map.cr_txe.read_and_write_to_u32(1, 0);
-        // TODO: let cr_val =  self.memory_map.cr_rxe.read_and_write_to_u32(1, 0); to enable read
+        let cr_val =  self.memory_map.cr_rxe.read_and_write_to_u32(1, cr_val);
+        // Again, see doc of CR register for the config process (P 185, doc BCM2835)
         self.memory_map.cr.write_without_read(cr_val);
         
         // Start the UART
@@ -67,11 +68,16 @@ impl<'a> UartInner<'a> {
         self.memory_map.fr_busy.read() != 0
     }
 
-    /// Test if the the TX FIFO is full.
+    /// Test if the TX FIFO is full.
     fn is_tx_full(&self) -> bool {
         self.memory_map.fr_txff.read() != 0
     }
 
+    /// Test if the RX FIFO is empty
+    fn is_rx_empty(&self) -> bool {
+        self.memory_map.fr_rxfe.read() != 0
+    }
+
     /// Write a character to the Uart
     fn write_char(&self, c: char) {
         if !self.initialized {
@@ -85,12 +91,28 @@ impl<'a> UartInner<'a> {
         self.memory_map.dr_data.write_without_read(c as u32);
     }
 
-    /// Flush the uart
+    /// Read a character from the UART.
+    /// Blocking.
+    fn blocking_read_char(&self) -> char {
+        while self.is_rx_empty() {
+            unsafe { asm!("nop") };
+        }
+        self.memory_map.dr_data.read() as u8 as char
+    }
+
+    /// Flush the output of the uart
     fn flush(&self) {
         while self.is_busy() {
             unsafe { asm!("nop") };
         }
     }
+
+    /// Flush the input of the uart
+    fn flush_input(&self) {
+        while !self.is_rx_empty() {
+            let _ = self.memory_map.dr_data.read() as u8 as char;
+        }
+    }
 }
 
 // Allow the use of uart for fmt::Write::write_fmt.
@@ -122,10 +144,12 @@ impl Write for Uart<'_> {
 
 impl Read for Uart<'_> {
     fn read_char(&self) -> char {
-        todo!()
+        self.inner.lock(|uart| uart.blocking_read_char())
     }
 
-    fn flush_input(&self) {}
+    fn flush_input(&self) {
+        self.inner.lock(|uart| uart.flush_input())
+    }
 }
 
 impl<'a> Uart<'a> {

src/main.rs

@@ -27,9 +27,9 @@ use core::arch::global_asm;
 use core::arch::asm;
 
 // TODO: handle this with features
-use crate::bsp::qemu::console::console;
-//#[cfg(not(test))]
-//use crate::bsp::rpi3::uart::console;
+//use crate::bsp::qemu::console::console;
+#[cfg(not(test))]
+use crate::bsp::rpi3::uart::console;
 #[cfg(not(test))]
 use crate::bsp::rpi3::gpio;
 
@@ -66,7 +66,7 @@ pub unsafe fn _start_rust() -> ! {
     match gpio::set_pin_output_state(20, gpio::PinOutputState::Low) {
         _ => (),
     }
-    //bsp::rpi3::uart::init();
+    bsp::rpi3::uart::init();
     println!("Hello there");
 
     let mut buffer = ['X'; 200];