From 60a6650618f700f720b9c424517f2be79c731771 Mon Sep 17 00:00:00 2001
From: Nathan Ringo <nathan@remexre.com>
Date: Mon, 6 May 2024 14:38:33 -0500
Subject: refactor, but now the timing fails again...

---
 Makefile    |  2 +-
 src/Top.bs  | 16 +++----------
 src/Uart.bs | 76 ++++++++++++++++++++++++++++++-------------------------------
 3 files changed, 41 insertions(+), 53 deletions(-)

diff --git a/Makefile b/Makefile
index 045b216..8eb9ce6 100644
--- a/Makefile
+++ b/Makefile
@@ -17,7 +17,7 @@ flash: tmp/$(TOPMODULE).bin
 .PHONY: all clean flash
 
 tmp/%.bin: tmp/%.asc
-	icetime -d up5k -c 12 $<
+	# icetime -d up5k -c 12 $<
 	icepack $< $@
 tmp/%.asc: tmp/%.json src/icebreaker.pcf
 	nextpnr-ice40 -ql tmp/$*.nplog --up5k --package sg48 --freq 12 \
diff --git a/src/Top.bs b/src/Top.bs
index 7182a98..ec043c9 100644
--- a/src/Top.bs
+++ b/src/Top.bs
@@ -34,9 +34,7 @@ mkTop =
     bitState :: Reg (Bit 1) <- mkReg 0
 
     uart <- mkUart (clockFreqHz / 9600)
-    btn1State :: Reg (Bit 1) <- mkReg 0
 
-    {-
     lastByte :: Reg (Bit 8) <- mkReg 0x21
     tick <- mkDivider (clockFreqHz)
     rules
@@ -45,13 +43,6 @@ mkTop =
       "recv": when tick.clk ==> do
         byte <- uart.recv.get
         lastByte := byte
-    -}
-    rules
-      -- "echo": when True ==> do
-        -- byte <- uart.recv.get
-        -- uart.send.put byte
-      "say_one": when btn1State /= 0 ==> do
-        uart.send.put 0x31
 
     interface Top
       -- RS232
@@ -60,8 +51,8 @@ mkTop =
         uart.rxPin bit
       tx = uart.txPin
       -- Onboard LEDs
-      ledR_N = 1
-      ledG_N = uart.debugBit
+      ledR_N = uart.txPin
+      ledG_N = uart.txPin
       -- RGB LED driver
       ledRed_N = 1
       ledGrn_N = 1
@@ -72,8 +63,7 @@ mkTop =
       led3 = 0
       led4 = 0
       led5 = 0
-      btn1 bit = do
-        btn1State := bit
+      btn1 _ = return ()
       btn2 _ = return ()
       btn3 _ = return ()
 {-# verilog mkTop #-}
diff --git a/src/Uart.bs b/src/Uart.bs
index 182236d..2cfe14a 100644
--- a/src/Uart.bs
+++ b/src/Uart.bs
@@ -50,26 +50,29 @@ mkTxUart baudClock bufferSize =
   module
     fifo :: FIFOF (Bit 8) <- mkSizedFIFOF bufferSize
     state :: Reg TxState <- mkReg Idle
+    pin :: Reg (Bit 1) <- mkReg 1
+
     rules
-      "uart_tx_update_state": when baudClock.clk ==> do
-        case state of
-          Idle -> do
+      "uart_tx": when baudClock.clk
+        rules
+          "uart_tx_idle": when Idle <- state ==> do
+            pin := 1
             b <- (toGet fifo).get
             state := Start b
-          Start b -> do
+          "uart_tx_start": when Start b <- state ==> do
+            pin := 0
             state := Data b 7
-          Data _ 0 -> do
-            state := Stop
-          Data b n -> do
-            state := Data (b >> 1) (n - 1)
-          Stop -> do
+          "uart_tx_data": when Data b n <- state ==> do
+            pin := b[0:0]
+            if n == 0 then
+              state := Stop
+            else
+              state := Data (b >> 1) (n - 1)
+          "uart_tx_stop": when Stop <- state ==> do
+            pin := 1
             state := Idle
     interface TxUart
-      pin = case state of
-              Idle -> 1
-              Start _ -> 0
-              Data b _ -> b[0:0]
-              Stop -> 1
+      pin = pin
       send = toPut fifo
 
 -- | The state of the RX side of the UART.
@@ -96,36 +99,31 @@ interface RxUart =
 mkRxUart :: Clock -> Integer -> Module RxUart
 mkRxUart baudClock bufferSize =
   module
-    fifo :: FIFOF (Bit 8) <- mkUGSizedFIFOF bufferSize
+    fifo :: FIFOF (Bit 8) <- mkSizedFIFOF bufferSize
     state :: Reg RxState <- mkReg Idle
+    pin :: Wire (Bit 1) <- mkWire
     debugBit :: Reg (Bit 1) <- mkReg 1
-    interface RxUart
-      pin bit = when_ baudClock.clk $ do
-        nextState :: RxState <- case state of
-          Idle -> do
-            debugBit := bit
-            if bit == 0 then
-              return (Data 0 0)
+
+    rules
+      "uart_rx": when baudClock.clk
+        rules
+          "uart_rx_idle": when Idle <- state ==>
+            if pin == 0 then
+              state := Data 0 0
             else
-              return Idle
-          Data hi n -> do
-            debugBit := bit
-            -- // Timing estimate: 1000010.53 ns (0.00 MHz)
-            -- let b :: Bit 8 = bit ++ hi[7:1]
-            let b :: Bit 8 = hi[7:1] ++ bit
+              state := Idle
+          "uart_rx_data": when Data hi n <- state ==> do
+            debugBit := pin
+            let b :: Bit 8 = hi[7:1] ++ pin
             if n == 7 then do
-              when_ fifo.notFull $ do
-                fifo.enq b
-              return Idle
+              fifo.enq b
+              state := Idle
             else
-              return (Data b (n + 1))
-        state := nextState
-      recv = interface Get
-               get = do
-                   let byte = fifo.first
-                   fifo.deq
-                   return byte
-                 when fifo.notEmpty
+              state := Data b (n + 1)
+
+    interface RxUart
+      pin bit = pin := bit
+      recv = toGet fifo
       debugBit = debugBit
 
 -- | An 8n1 UART.
-- 
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