add component library with UART

default.nix

@@ -1,6 +1,7 @@
 { pkgs ? import <nixpkgs> {}}:
 rec {
-	nmigen = pkgs.callPackage ./nmigen.nix {};
-	jtagtap = pkgs.callPackage ./jtagtap.nix { inherit nmigen; };
-	minerva = pkgs.callPackage ./minerva.nix { inherit nmigen; inherit jtagtap; };
+  nmigen = pkgs.callPackage ./nmigen.nix {};
+  jtagtap = pkgs.callPackage ./jtagtap.nix { inherit nmigen; };
+  minerva = pkgs.callPackage ./minerva.nix { inherit nmigen; inherit jtagtap; };
+  heavycomps = pkgs.callPackage ./heavycomps.nix { inherit nmigen; };
 }

heavycomps.nix

@@ -0,0 +1,16 @@
+{ stdenv, python3Packages, nmigen }:
+
+python3Packages.buildPythonPackage {
+  name = "heavycomps";
+
+  src = ./heavycomps;
+
+  propagatedBuildInputs = [ nmigen ];
+
+  meta = with stdenv.lib; {
+    description = "Components for the HeavyX SoC toolkit";
+    homepage    = "https://m-labs.hk/migen";
+    license     = licenses.bsd2;
+    maintainers = [ maintainers.sb0 ];
+  };
+}

heavycomps/heavycomps/uart.py

@@ -0,0 +1,110 @@
+from nmigen import *
+from nmigen.lib.cdc import MultiReg
+from nmigen.cli import main
+
+
+class RS232RX:
+    def __init__(self, tuning_word):
+        self.rx = Signal()
+        self.data = Signal(8)
+        self.stb = Signal()
+        self.tuning_word = tuning_word
+
+    def elaborate(self, platform):
+        m = Module()
+
+        uart_clk_rxen = Signal()
+        phase_accumulator_rx = Signal(32)
+
+        rx = Signal()
+        m.submodules += MultiReg(self.rx, rx)
+        rx_r = Signal()
+        rx_reg = Signal(8)
+        rx_bitcount = Signal(4)
+        rx_busy = Signal()
+        rx_done = self.stb
+        rx_data = self.data
+        m.d.sync += rx_done.eq(0)
+        m.d.sync += rx_r.eq(rx)
+        with m.If(~rx_busy):
+            with m.If(~rx & rx_r):  # look for start bit
+                m.d.sync += rx_busy.eq(1)
+                m.d.sync += rx_bitcount.eq(0)
+        with m.Else():
+            with m.If(uart_clk_rxen):
+                m.d.sync += rx_bitcount.eq(rx_bitcount + 1)
+                with m.If(rx_bitcount == 0):
+                    with m.If(rx):  # verify start bit
+                        m.d.sync += rx_busy.eq(0)
+                with m.Elif(rx_bitcount == 9):
+                    m.d.sync += rx_busy.eq(0)
+                    with m.If(rx):  # verify stop bit
+                        m.d.sync += rx_data.eq(rx_reg)
+                        m.d.sync += rx_done.eq(1)
+                with m.Else():
+                    m.d.sync += rx_reg.eq(Cat(rx_reg[1:], rx))
+        with m.If(rx_busy):
+            m.d.sync += Cat(phase_accumulator_rx, uart_clk_rxen).eq(phase_accumulator_rx + self.tuning_word)
+        with m.Else():
+            m.d.sync += Cat(phase_accumulator_rx, uart_clk_rxen).eq(2**31)
+
+        return m
+
+
+class RS232TX:
+    def __init__(self, tuning_word):
+        self.tx = Signal(reset=1)
+        self.data = Signal(8)
+        self.stb = Signal()
+        self.ack = Signal()
+        self.tuning_word = tuning_word
+
+    def elaborate(self, platform):
+        m = Module()
+
+        uart_clk_txen = Signal()
+        phase_accumulator_tx = Signal(32)
+
+        tx_reg = Signal(8)
+        tx_bitcount = Signal(4)
+        tx_busy = Signal()
+        m.d.sync += self.ack.eq(0),
+        with m.If(self.stb & ~tx_busy & ~self.ack):
+            m.d.sync += tx_reg.eq(self.data)
+            m.d.sync += tx_bitcount.eq(0)
+            m.d.sync += tx_busy.eq(1)
+            m.d.sync += self.tx.eq(0)
+        with m.Elif(uart_clk_txen & tx_busy):
+            m.d.sync += tx_bitcount.eq(tx_bitcount + 1)
+            with m.If(tx_bitcount == 8):
+                m.d.sync += self.tx.eq(1)
+            with m.Elif(tx_bitcount == 9):
+                m.d.sync += self.tx.eq(1)
+                m.d.sync += tx_busy.eq(0)
+                m.d.sync += self.ack.eq(1),
+            with m.Else():
+                m.d.sync += self.tx.eq(tx_reg[0])
+                m.d.sync += tx_reg.eq(Cat(tx_reg[1:], 0))
+        with m.If(tx_busy):
+            m.d.sync += Cat(phase_accumulator_tx, uart_clk_txen).eq(phase_accumulator_tx + self.tuning_word)
+        with m.Else():
+            m.d.sync += Cat(phase_accumulator_tx, uart_clk_txen).eq(0)
+
+        return m
+
+
+class Loopback:
+    def elaborate(self, platform):
+        m = Module()
+        tuning_word = 2**31
+        tx = RS232TX(tuning_word)
+        rx = RS232RX(tuning_word)
+        m.submodules += tx, rx
+        m.d.comb += rx.rx.eq(tx.tx)
+        m.d.comb += tx.data.eq(42)
+        m.d.comb += tx.stb.eq(1)
+        return m
+
+if __name__ == "__main__":
+    uart = Loopback()
+    main(uart)

heavycomps/setup.py

@@ -0,0 +1,7 @@
+from setuptools import setup, find_packages
+
+setup(
+    name="heavycomps",
+    install_requires=["nmigen"],
+    packages=find_packages()
+)