Add initial SiSpeed Tang Nano 4K support (Led blink only for now...).

./sispeed_tang_nano_4k.py --build --load

Build with Gowin EDA.
Load with OpenFPGALoader.

litex_boards/__init__.py

@@ -27,6 +27,7 @@ vendors = [
     "saanlima",
     "scarabhardware",
     "siglent",
+    "sispeed",
     "sqrl",
     "terasic",
     "trenz",

litex_boards/platforms/sispeed_tang_nano_4k.py

@@ -0,0 +1,43 @@
+#
+# This file is part of LiteX-Boards.
+#
+# Copyright (c) 2021 Florent Kermarrec <florent@enjoy-digital.fr>
+# SPDX-License-Identifier: BSD-2-Clause
+
+from migen import *
+
+from litex.build.generic_platform import *
+from litex.build.gowin.platform import GowinPlatform
+from litex.build.openfpgaloader import OpenFPGALoader
+
+# IOs ----------------------------------------------------------------------------------------------
+
+_io = [
+    # Clk / Rst
+    ("clk27",  0, Pins("45"), IOStandard("LVCMOS33")),
+    ("rst_n",  0, Pins("15"), IOStandard("LVCMOS33")),
+
+    # Leds
+    ("user_led", 0, Pins("10"), IOStandard("LVCMOS33")),
+]
+
+# Connectors ---------------------------------------------------------------------------------------
+
+_connectors = []
+
+# Platform -----------------------------------------------------------------------------------------
+
+class Platform(GowinPlatform):
+    default_clk_name   = "clk27"
+    default_clk_period = 1e9/27e6
+
+    def __init__(self):
+        GowinPlatform.__init__(self, "GW1NSR-LV4CQN48PC7/I6", _io, _connectors, toolchain="gowin", devicename="GW1NSR-4C")
+        self.toolchain.options["use_mode_as_gpio"] = 1
+
+    def create_programmer(self):
+        return OpenFPGALoader("tangnano")
+
+    def do_finalize(self, fragment):
+        GowinPlatform.do_finalize(self, fragment)
+        self.add_period_constraint(self.lookup_request("clk27", loose=True), 1e9/100e6)

litex_boards/targets/sispeed_tang_nano_4k.py

@@ -0,0 +1,85 @@
+#!/usr/bin/env python3
+
+#
+# This file is part of LiteX-Boards.
+#
+# Copyright (c) 2021 Florent Kermarrec <florent@enjoy-digital.fr>
+# SPDX-License-Identifier: BSD-2-Clause
+
+import os
+import argparse
+
+from migen import *
+from migen.genlib.resetsync import AsyncResetSynchronizer
+
+from litex.soc.integration.soc_core import *
+from litex.soc.integration.builder import *
+from litex.soc.cores.led import LedChaser
+
+from litex_boards.platforms import tang_nano_4k
+
+# CRG ----------------------------------------------------------------------------------------------
+
+class _CRG(Module):
+    def __init__(self, platform, sys_clk_freq):
+        self.rst = Signal()
+        self.clock_domains.cd_sys   = ClockDomain()
+
+        # # #
+
+        # Clk / Rst
+        clk27 = platform.request("clk27")
+        rst_n = platform.request("rst_n")
+        self.comb += self.cd_sys.clk.eq(clk27)
+        self.specials += AsyncResetSynchronizer(self.cd_sys, ~rst_n)
+
+# BaseSoC ------------------------------------------------------------------------------------------
+
+class BaseSoC(SoCCore):
+    def __init__(self, sys_clk_freq=int(27e6), with_led_chaser=True, **kwargs):
+        platform = tang_nano_4k.Platform()
+
+        # Disable CPU/UART for now.
+        kwargs["cpu_type"]  = None
+        kwargs["with_uart"] = False
+
+        # SoCCore ----------------------------------------------------------------------------------
+        SoCCore.__init__(self, platform, sys_clk_freq,
+            ident         = "LiteX SoC on Tang Nano 4K",
+            ident_version = True,
+            **kwargs)
+
+        # CRG --------------------------------------------------------------------------------------
+        self.submodules.crg = _CRG(platform, sys_clk_freq)
+
+        # Leds -------------------------------------------------------------------------------------
+        if with_led_chaser:
+            self.submodules.leds = LedChaser(
+                pads         = platform.request_all("user_led"),
+                sys_clk_freq = sys_clk_freq)
+
+# Build --------------------------------------------------------------------------------------------
+
+def main():
+    parser = argparse.ArgumentParser(description="LiteX SoC on Tang Nano 4K")
+    parser.add_argument("--build",       action="store_true", help="Build bitstream")
+    parser.add_argument("--load",        action="store_true", help="Load bitstream")
+    parser.add_argument("--sys-clk-freq",default=27e6,        help="System clock frequency (default: 25MHz)")
+    builder_args(parser)
+    soc_core_args(parser)
+    args = parser.parse_args()
+
+    soc = BaseSoC(
+        sys_clk_freq      = int(float(args.sys_clk_freq)),
+        **soc_core_argdict(args)
+    )
+
+    builder = Builder(soc, **builder_argdict(args))
+    builder.build(run=args.build)
+
+    if args.load:
+        prog = soc.platform.create_programmer()
+        prog.load_bitstream(os.path.join(builder.gateware_dir, "impl", "pnr", "project.fs"))
+
+if __name__ == "__main__":
+    main()