Add Ethernet to your SoC with cheap Lan8720 RMII "PMOD"

digilent_arty_s7.py

#!/usr/bin/env python3

#
# This file is part of LiteX-Boards.
#
# Copyright (c) 2015-2019 Florent Kermarrec <[email protected]>,
# Copyright (c) 2020 Staf Verhaegen <[email protected]>
# SPDX-License-Identifier: BSD-2-Clause

import os
import argparse

from migen import *

from litex_boards.platforms import arty_s7
from litex.build.xilinx.vivado import vivado_build_args, vivado_build_argdict

from litex.soc.cores.clock import *
from litex.soc.integration.soc_core import *
from litex.soc.integration.builder import *
from litex.soc.cores.led import LedChaser

from litedram.modules import MT41K128M16
from litedram.phy import s7ddrphy

# CRG ----------------------------------------------------------------------------------------------

class _CRG(Module):
    def __init__(self, platform, sys_clk_freq):
        self.rst = Signal()
        self.clock_domains.cd_sys       = ClockDomain()
        self.clock_domains.cd_sys2x     = ClockDomain(reset_less=True)
        self.clock_domains.cd_sys4x     = ClockDomain(reset_less=True)
        self.clock_domains.cd_sys4x_dqs = ClockDomain(reset_less=True)
        self.clock_domains.cd_idelay    = ClockDomain()

        # # #

        self.submodules.pll = pll = S7PLL(speedgrade=-1)
        self.comb += pll.reset.eq(~platform.request("cpu_reset") | self.rst)
        pll.register_clkin(platform.request("clk100"), 100e6)
        pll.create_clkout(self.cd_sys,       sys_clk_freq)
        pll.create_clkout(self.cd_sys2x,     2*sys_clk_freq)
        pll.create_clkout(self.cd_sys4x,     4*sys_clk_freq)
        pll.create_clkout(self.cd_sys4x_dqs, 4*sys_clk_freq, phase=90)
        pll.create_clkout(self.cd_idelay,    200e6)
        platform.add_false_path_constraints(self.cd_sys.clk, pll.clkin) # Ignore sys_clk to pll.clkin path created by SoC's rst.

        self.submodules.idelayctrl = S7IDELAYCTRL(self.cd_idelay)

# BaseSoC ------------------------------------------------------------------------------------------

class BaseSoC(SoCCore):
    def __init__(self, variant="s7-50", sys_clk_freq=int(100e6), **kwargs):
        platform = arty_s7.Platform(variant=variant)

        # SoCCore ----------------------------------------------------------------------------------
        SoCCore.__init__(self, platform, sys_clk_freq,
            ident          = "LiteX SoC on Arty S7",
            ident_version  = True,
            **kwargs)

        # CRG --------------------------------------------------------------------------------------
        self.submodules.crg = _CRG(platform, sys_clk_freq)

        # DDR3 SDRAM -------------------------------------------------------------------------------
        if not self.integrated_main_ram_size:
            self.submodules.ddrphy = s7ddrphy.A7DDRPHY(platform.request("ddram"),
                memtype        = "DDR3",
                nphases        = 4,
                sys_clk_freq   = sys_clk_freq)
            self.add_sdram("sdram",
                phy           = self.ddrphy,
                module        = MT41K128M16(sys_clk_freq, "1:4"),
                l2_cache_size = kwargs.get("l2_size", 8192)
            )

        # Ethernet ---------------------------------------------------------------------------------

        # Add IOs to Board's platform.

        from litex.build.generic_platform import Pins, Subsignal, IOStandard
        def eth_lan8720_rmii_pmod_io(pmod):
            # Lan8020 RMII PHY "PMOD": To be used as a PMOD, MDIO should be disconnected and TX1
            # connected to PMOD8 IO.
            return [

                ("eth_clocks", 0,
                    Subsignal("ref_clk", Pins(f"{pmod}:6")),
                    IOStandard("LVCMOS33"),
                ),
                ("eth", 0,
                    Subsignal("rx_data", Pins(f"{pmod}:5 {pmod}:1")),
                    Subsignal("crs_dv",  Pins(f"{pmod}:2")),
                    Subsignal("tx_en",   Pins(f"{pmod}:4")),
                    Subsignal("tx_data", Pins(f"{pmod}:0 {pmod}:7")),
                    IOStandard("LVCMOS33")
                 ),
            ]
        platform.add_extension(eth_lan8720_rmii_pmod_io("pmodb"))

        # Create RMII Ethernet PHY.
        from liteeth.phy.rmii import LiteEthPHYRMII
        self.submodules.ethphy = LiteEthPHYRMII(
            clock_pads = platform.request("eth_clocks"),
            pads       = platform.request("eth"),
            refclk_cd  = None)

        # Add Ethernet MAC and connect it to the Soft-CPU.
        #self.add_ethernet(phy=self.ethphy)

        # Add Etherbone and connect if to the SoC.
        self.add_etherbone(phy=self.ethphy)

        # Leds -------------------------------------------------------------------------------------
        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 Arty S7")
    parser.add_argument("--build",        action="store_true", help="Build bitstream")
    parser.add_argument("--load",         action="store_true", help="Load bitstream")
    parser.add_argument("--variant",      default="s7-50",     help="Board variant: s7-50 (default) or s7-25")
    parser.add_argument("--sys-clk-freq", default=100e6,       help="System clock frequency (default: 100MHz)")
    builder_args(parser)
    soc_core_args(parser)
    vivado_build_args(parser)
    args = parser.parse_args()

    soc = BaseSoC(
        variant      = args.variant,
        sys_clk_freq = int(float(args.sys_clk_freq)),
        **soc_core_argdict(args)
    )
    builder = Builder(soc, **builder_argdict(args))
    builder.build(**vivado_build_argdict(args), run=args.build)

    if args.load:
        prog = soc.platform.create_programmer()
        prog.load_bitstream(os.path.join(builder.gateware_dir, soc.build_name + ".bit"))

if __name__ == "__main__":
    main()