Uart now has correct write implementation presumably

c/uart_sim_device.c

@@ -8,6 +8,8 @@
 static volatile bool ctrl_c_received = false;
 static char last_char = '\0';
 
+int is_char_available();
+
 void sigint_handler(int sig_num) {
     ctrl_c_received = true;
 }

hello.asm

@@ -1,22 +0,0 @@
-
-./rv_tests/hello_world/hello.bin:     file format binary
-
-
-Disassembly of section .data:
-
-0000000000000000 <.data>:
-   0:	00000597          	auipc	a1,0x0
-   4:	02458593          	add	a1,a1,36 # 0x24
-   8:	0005c503          	lbu	a0,0(a1)
-   c:	00050a63          	beqz	a0,0x20
-  10:	100002b7          	lui	t0,0x10000
-  14:	00a28023          	sb	a0,0(t0) # 0x10000000
-  18:	00158593          	add	a1,a1,1
-  1c:	fedff06f          	j	0x8
-  20:	0000006f          	j	0x20
-  24:	6548                	ld	a0,136(a0)
-  26:	6c6c                	ld	a1,216(s0)
-  28:	77202c6f          	jal	s8,0x279a
-  2c:	646c726f          	jal	tp,0xc7672
-  30:	0a21                	add	s4,s4,8
-	...

hs/Bus.hs

@@ -4,6 +4,7 @@ module Bus() where
 import Clash.Prelude
 
 import Peripherals.Ram(Ram, RamLine, read, RamAddr)
+import Peripherals.Uart(UartAddr, read)
 import Machine(Peripherals(..))
 import BusTypes(
     BusError(..),
@@ -35,10 +36,19 @@ alignCheck addr SizeQuadWord   = addr `mod` 16 == 0
 read :: Request -> Peripherals -> IO ReadResponse
 read (Request addr size) peripherals
   | not (alignCheck addr size) = return $ ReadResponse $ Error UnAligned
-  | (addr > ramStart) && (addr < ramEnd) =
-    return $ ReadResponse $ Result $ Peripherals.Ram.read size ramAddr (ram peripherals)
+  | (addr >= ramStart) && (addr <= ramEnd) =
+    return        $
+    ReadResponse  $
+    Result        $ Peripherals.Ram.read size ramAddr (ram peripherals)
+  | (addr >= uartStart) && (addr <= uartEnd) =
+     ReadResponse . Result <$>
+     Peripherals.Uart.read size uartAddr
   | otherwise = return $ ReadResponse $ Error UnMapped
     where
       ramAddrNoOffset = addr - ramStart
       ramAddr :: RamAddr
       ramAddr = resize ramAddrNoOffset
+
+      uartAddrNoOffset = addr - uartStart
+      uartAddr :: UartAddr
+      uartAddr = resize uartAddrNoOffset

hs/Peripherals/Uart.hs

@@ -1,8 +1,8 @@
-module Peripherals.Uart (read) where
+module Peripherals.Uart (read, write, UartAddr) where
 
 import Clash.Prelude hiding (read)
 import Types (Byte)
-import Data.Char (ord)
+import Data.Char (ord, chr)
 
 import Peripherals.UartCFFI (
     initTerminal,
@@ -20,6 +20,7 @@ import BusTypes (
     ReadResponse(..),
     WriteResponse(..)
   )
+import GHC.Generics (URec(UAddr), Generic (from))
 
 -- based on a 16550 UART which has an address space of 8 bytes
 type UartAddr = Unsigned 3
@@ -28,6 +29,9 @@ type UartAddr = Unsigned 3
 rbrAddr :: UartAddr
 rbrAddr = 0x0
 
+thrAddr :: UartAddr
+thrAddr = 0x0
+
 -- Line Status Register address
 lsrAddr :: UartAddr
 lsrAddr = 0x5
@@ -50,8 +54,11 @@ buildRBR = do
 -- Reads the Line Status Register (LSR) to check character availability
 buildLSR :: IO Byte
 buildLSR = do
-  char_available <- isCharAvailable
-  return $ fromIntegral char_available
+  (char_available :: Byte) <- fromIntegral <$> isCharAvailable
+  -- highly unlikely that we overflow stdout buffer, so we set
+  -- transmit to always ready
+  let (transmit_ready :: Byte) = 0b0010_0000
+  return (char_available .|. transmit_ready)
 
 -- Updated 'read' function to handle RBR and LSR reads
 read :: TransactionSize -> UartAddr -> IO BusVal
@@ -59,3 +66,18 @@ read size addr
   | addr == rbrAddr = busValFromByte size <$> buildRBR
   | addr == lsrAddr = busValFromByte size <$> buildLSR
   | otherwise       = return $ busValFromByte size 0x00
+
+extractLowestByte :: BusVal -> Byte
+extractLowestByte (BusByte b)       = b
+extractLowestByte (BusHalfWord hw)  = resize hw
+extractLowestByte (BusFullWord fw)  = resize fw
+extractLowestByte (BusDoubleWord dw) = resize dw
+extractLowestByte (BusQuadWord qw)   = resize qw
+
+byteToChar :: Byte -> Char
+byteToChar = chr . fromIntegral
+
+write :: BusVal -> UartAddr -> IO ()
+write val addr
+  | addr == thrAddr = writeCharToTerminal $ byteToChar $ extractLowestByte val
+  | otherwise = return ()

rv_tests/hello_world/Makefile

@@ -34,7 +34,7 @@ $(BIN): $(ELF)
 # Run in QEMU
 run: $(BIN)
 	echo "Press CTRL+A then X to exit QEMU"
-	$(QEMU) -machine virt -nographic -bios none -kernel $(BIN) -device loader,file=$(BIN),addr=0x80000000 -device sifive_uart
+	$(QEMU) -machine virt -nographic -bios none -kernel $(BIN) -device loader,file=$(BIN),addr=0x80000000
 
 # Clean up generated files
 clean: