add opencores uart16550 instance wrapper

diff --git a/src/soc/bus/uart_16550.py b/src/soc/bus/uart_16550.py
new file mode 100644 (file)
index 0000000..8c89083
--- /dev/null
+++ b/src/soc/bus/uart_16550.py
@@ -0,0 +1,106 @@
+#!/usr/bin/env python3
+#
+# SPDX-License-Identifier: LGPLv3+
+# Copyright (C) 2022 Luke Kenneth Casson Leighton <lkcl@lkcl.net>
+# Sponsored by NLnet and NGI POINTER under EU Grants 871528 and 957073
+# Part of the Libre-SOC Project.
+#
+# this is a wrapper around the opencores verilog uart16550 module
+
+from nmigen import (Elaboratable, Cat, Module, Signal, ClockSignal, Instance,
+                    ResetSignal)
+
+from nmigen_soc.wishbone.bus import Interface
+from nmigen.cli import rtlil, verilog
+
+__all__ = ["UART16550"]
+
+
+class UART16550(Elaboratable):
+    """16550 UART from opencores, nmigen wrapper
+    """
+
+    def __init__(self, bus=None, features=None, name=None):
+        if name is not None:
+            # convention: give the name in the format "name_number"
+            self.idx = int(name.split("_")[-1])
+        else:
+            self.idx = 0
+
+        # set up the wishbone bus
+        if features is None:
+            features = frozenset()
+        if bus is None:
+            bus = Interface(addr_width=5,
+                            data_width=32,
+                            features=features,
+                            name=name+"_wb_%d" % self.idx)
+        self.bus = bus
+        assert len(self.bus.dat_r) == 32, "bus width must be 32"
+
+        # IRQ for data buffer receive/xmit
+        self.irq = Signal() 
+
+        # 9-pin UART signals (if anyone still remembers those...)
+        self.tx_o = Signal() # transmit
+        self.rx_i = Signal() # receive
+        self.rts_o = Signal() # ready to send
+        self.cts_i = Signal() # clear to send
+        self.dtr_o = Signal() # data terminal ready
+        self.dsr_i = Signal() # data send ready
+        self.ri_i = Signal() # can't even remember what this is!
+        self.dcd_i = Signal() # or this!
+
+    def elaborate(self, platform):
+        m = Module()
+
+        # create external verilog 16550 uart here
+        idx, bus = self.idx, self.bus
+        uart = Instance("uart_top_%d" % idx, 
+                            i_wb_clk_i=ClockSignal(),
+                            i_wb_rst_i=ResetSignal(),
+                            i_wb_adr_i=bus.adr,
+                            i_wb_dat_i=bus.dat_w,
+                            i_wb_sel_i=bus.sel,
+                            o_wb_dat_o=bus.dat_r,
+                            i_wb_we_i=bus.we,
+                            i_wb_stb_i=bus.stb,
+                            i_wb_cyc_i=bus.cyc,
+                            o_wb_ack_o=bus.ack,
+                            o_int_o=self.irq,
+                            o_stx_pad_o=self.tx_o,
+                            i_srx_pad_i=self.rx_i,
+                            o_rts_pad_o=self.rts_o,
+                            i_cts_pad_i=self.cts_i,
+                            o_dtr_pad_o=self.dtr_o,
+                            i_dsr_pad_i=self.dsr_i,
+                            i_ri_pad_i=self.ri_i,
+                            i_dcd_pad_i=self.dcd_i
+                            );
+
+        m.submodules['uart16550_%d' % self.idx] = uart
+
+        return m
+
+
+def create_ilang(dut, ports, test_name):
+    vl = rtlil.convert(dut, name=test_name, ports=ports)
+    with open("%s.il" % test_name, "w") as f:
+        f.write(vl)
+
+def create_verilog(dut, ports, test_name):
+    vl = verilog.convert(dut, name=test_name, ports=ports)
+    with open("%s.v" % test_name, "w") as f:
+        f.write(vl)
+
+
+if __name__ == "__main__":
+    uart = UART16550(name="uart_0")
+    create_ilang(uart, [uart.bus.cyc, uart.bus.stb, uart.bus.ack,
+                        uart.bus.dat_r, uart.bus.dat_w, uart.bus.adr,
+                        uart.bus.we, uart.bus.sel,
+                        uart.irq,
+                        uart.tx_o, uart.rx_i, uart.rts_o, uart.cts_i,
+                        uart.dtr_o, uart.dsr_i, uart.ri_i, uart.dcd_i
+                       ], "uart_0")
+