xfcp: Add XFCP UART interface module and testbench

Signed-off-by: Alex Forencich <alex@alexforencich.com>

tb/xfcp/taxi_xfcp_if_uart/Makefile

@@ -0,0 +1,47 @@
+# SPDX-License-Identifier: CERN-OHL-S-2.0
+#
+# Copyright (c) 2025 FPGA Ninja, LLC
+#
+# Authors:
+# - Alex Forencich
+
+TOPLEVEL_LANG = verilog
+
+SIM ?= verilator
+WAVES ?= 0
+
+COCOTB_HDL_TIMEUNIT = 1ns
+COCOTB_HDL_TIMEPRECISION = 1ps
+
+DUT      = taxi_xfcp_if_uart
+COCOTB_TEST_MODULES = test_$(DUT)
+COCOTB_TOPLEVEL     = test_$(DUT)
+MODULE   = $(COCOTB_TEST_MODULES)
+TOPLEVEL = $(COCOTB_TOPLEVEL)
+VERILOG_SOURCES += $(COCOTB_TOPLEVEL).sv
+VERILOG_SOURCES += ../../../rtl/xfcp/$(DUT).f
+
+# handle file list files
+process_f_file = $(call process_f_files,$(addprefix $(dir $1),$(shell cat $1)))
+process_f_files = $(foreach f,$1,$(if $(filter %.f,$f),$(call process_f_file,$f),$f))
+uniq_base = $(if $1,$(call uniq_base,$(foreach f,$1,$(if $(filter-out $(notdir $(lastword $1)),$(notdir $f)),$f,))) $(lastword $1))
+VERILOG_SOURCES := $(call uniq_base,$(call process_f_files,$(VERILOG_SOURCES)))
+
+# module parameters
+export PARAM_TX_FIFO_DEPTH := 512
+export PARAM_RX_FIFO_DEPTH := 512
+
+ifeq ($(SIM), icarus)
+	PLUSARGS += -fst
+
+	COMPILE_ARGS += $(foreach v,$(filter PARAM_%,$(.VARIABLES)),-P $(COCOTB_TOPLEVEL).$(subst PARAM_,,$(v))=$($(v)))
+else ifeq ($(SIM), verilator)
+	COMPILE_ARGS += $(foreach v,$(filter PARAM_%,$(.VARIABLES)),-G$(subst PARAM_,,$(v))=$($(v)))
+
+	ifeq ($(WAVES), 1)
+		COMPILE_ARGS += --trace-fst
+		VERILATOR_TRACE = 1
+	endif
+endif
+
+include $(shell cocotb-config --makefiles)/Makefile.sim

tb/xfcp/taxi_xfcp_if_uart/test_taxi_xfcp_if_uart.py

@@ -0,0 +1,201 @@
+#!/usr/bin/env python
+# SPDX-License-Identifier: CERN-OHL-S-2.0
+"""
+
+Copyright (c) 2025 FPGA Ninja, LLC
+
+Authors:
+- Alex Forencich
+
+"""
+
+import itertools
+import logging
+import os
+import sys
+
+import cocotb_test.simulator
+
+import cocotb
+from cocotb.clock import Clock
+from cocotb.triggers import RisingEdge
+from cocotb.regression import TestFactory
+
+from cocotbext.axi import AxiStreamBus, AxiStreamSource, AxiStreamSink
+from cocotbext.uart import UartSource, UartSink
+
+try:
+    from xfcp import XfcpFrame
+except ImportError:
+    # attempt import from current directory
+    sys.path.insert(0, os.path.join(os.path.dirname(__file__)))
+    try:
+        from xfcp import XfcpFrame
+    finally:
+        del sys.path[0]
+
+
+class TB(object):
+    def __init__(self, dut, baud=3e6):
+        self.dut = dut
+
+        self.log = logging.getLogger("cocotb.tb")
+        self.log.setLevel(logging.DEBUG)
+
+        cocotb.start_soon(Clock(dut.clk, 8, units="ns").start())
+
+        self.uart_source = UartSource(dut.uart_rxd, baud=baud, bits=8, stop_bits=1)
+        self.uart_sink = UartSink(dut.uart_txd, baud=baud, bits=8, stop_bits=1)
+
+        self.axis_source = AxiStreamSource(AxiStreamBus.from_entity(dut.dn_xfcp_in), dut.clk, dut.rst)
+        self.axis_sink = AxiStreamSink(AxiStreamBus.from_entity(dut.dn_xfcp_out), dut.clk, dut.rst)
+
+        dut.prescale.setimmediatevalue(int(1/8e-9/baud/8))
+
+    async def reset(self):
+        self.dut.rst.setimmediatevalue(0)
+        await RisingEdge(self.dut.clk)
+        await RisingEdge(self.dut.clk)
+        self.dut.rst.value = 1
+        await RisingEdge(self.dut.clk)
+        await RisingEdge(self.dut.clk)
+        self.dut.rst.value = 0
+        await RisingEdge(self.dut.clk)
+        await RisingEdge(self.dut.clk)
+
+
+async def run_test_tx(dut, payload_lengths=None, payload_data=None):
+
+    tb = TB(dut)
+
+    await tb.reset()
+
+    for test_data in [payload_data(x) for x in payload_lengths()]:
+
+        pkt = XfcpFrame()
+        pkt.path = [1, 2, 3]
+        pkt.rpath = [4]
+        pkt.ptype = 1
+        pkt.payload = test_data
+
+        await tb.axis_source.write(pkt.build())
+
+        rx_data = bytearray()
+        while True:
+            b = await tb.uart_sink.read(1)
+            if b[0] == 0:
+                break
+            rx_data.extend(b)
+
+        rx_pkt = XfcpFrame.parse_cobs(rx_data)
+
+        print(rx_pkt)
+        assert rx_pkt == pkt
+
+        assert tb.uart_sink.empty()
+
+    await RisingEdge(dut.clk)
+    await RisingEdge(dut.clk)
+
+
+async def run_test_rx(dut, payload_lengths=None, payload_data=None):
+
+    tb = TB(dut)
+
+    await tb.reset()
+
+    for test_data in [payload_data(x) for x in payload_lengths()]:
+
+        pkt = XfcpFrame()
+        pkt.path = [1, 2, 3]
+        pkt.rpath = [4]
+        pkt.ptype = 1
+        pkt.payload = test_data
+
+        await tb.uart_source.write(pkt.build_cobs())
+
+        rx_frame = await tb.axis_sink.recv()
+        rx_pkt = XfcpFrame.parse(rx_frame.tdata)
+
+        print(rx_pkt)
+        assert rx_pkt == pkt
+
+        assert tb.axis_sink.empty()
+
+    await RisingEdge(dut.clk)
+    await RisingEdge(dut.clk)
+
+
+def cycle_pause():
+    return itertools.cycle([1, 1, 1, 0])
+
+
+def size_list():
+    return list(range(1, 16)) + [128]
+
+
+def incrementing_payload(length):
+    return bytearray(itertools.islice(itertools.cycle(range(256)), length))
+
+
+if cocotb.SIM_NAME:
+
+    for test in [run_test_tx, run_test_rx]:
+        factory = TestFactory(test)
+        factory.add_option("payload_lengths", [size_list])
+        factory.add_option("payload_data", [incrementing_payload])
+        factory.generate_tests()
+
+
+# cocotb-test
+
+tests_dir = os.path.dirname(__file__)
+rtl_dir = os.path.abspath(os.path.join(tests_dir, '..', '..', '..', 'rtl'))
+
+
+def process_f_files(files):
+    lst = {}
+    for f in files:
+        if f[-2:].lower() == '.f':
+            with open(f, 'r') as fp:
+                l = fp.read().split()
+            for f in process_f_files([os.path.join(os.path.dirname(f), x) for x in l]):
+                lst[os.path.basename(f)] = f
+        else:
+            lst[os.path.basename(f)] = f
+    return list(lst.values())
+
+
+def test_taxi_xfcp_if_uart(request):
+
+    dut = "taxi_xfcp_if_uart"
+    module = os.path.splitext(os.path.basename(__file__))[0]
+    toplevel = module
+
+    verilog_sources = [
+        os.path.join(tests_dir, f"{toplevel}.sv"),
+        os.path.join(rtl_dir, "xfcp", f"{dut}.f"),
+    ]
+
+    verilog_sources = process_f_files(verilog_sources)
+
+    parameters = {}
+
+    parameters['TX_FIFO_DEPTH'] = 512
+    parameters['RX_FIFO_DEPTH'] = 512
+
+    extra_env = {f'PARAM_{k}': str(v) for k, v in parameters.items()}
+
+    sim_build = os.path.join(tests_dir, "sim_build",
+        request.node.name.replace('[', '-').replace(']', ''))
+
+    cocotb_test.simulator.run(
+        simulator="verilator",
+        python_search=[tests_dir],
+        verilog_sources=verilog_sources,
+        toplevel=toplevel,
+        module=module,
+        parameters=parameters,
+        sim_build=sim_build,
+        extra_env=extra_env,
+    )

tb/xfcp/taxi_xfcp_if_uart/test_taxi_xfcp_if_uart.sv

@@ -0,0 +1,65 @@
+// SPDX-License-Identifier: CERN-OHL-S-2.0
+/*
+
+Copyright (c) 2025 FPGA Ninja, LLC
+
+Authors:
+- Alex Forencich
+
+*/
+
+`resetall
+`timescale 1ns / 1ps
+`default_nettype none
+
+/*
+ * XFCP Interface (UART) testbench
+ */
+module test_taxi_xfcp_if_uart #
+(
+    /* verilator lint_off WIDTHTRUNC */
+    parameter TX_FIFO_DEPTH = 512,
+    parameter RX_FIFO_DEPTH = 512
+    /* verilator lint_on WIDTHTRUNC */
+)
+();
+
+logic clk;
+logic rst;
+
+logic uart_rxd;
+logic uart_txd;
+
+taxi_axis_if #(.DATA_W(8), .LAST_EN(1), .USER_EN(1), .USER_W(1)) dn_xfcp_in(), dn_xfcp_out();
+
+logic [15:0] prescale;
+
+taxi_xfcp_if_uart #(
+    .TX_FIFO_DEPTH(TX_FIFO_DEPTH),
+    .RX_FIFO_DEPTH(RX_FIFO_DEPTH)
+)
+uut (
+    .clk(clk),
+    .rst(rst),
+
+    /*
+     * UART interface
+     */
+    .uart_rxd(uart_rxd),
+    .uart_txd(uart_txd),
+
+    /*
+     * XFCP downstream port
+     */
+    .dn_xfcp_in(dn_xfcp_in),
+    .dn_xfcp_out(dn_xfcp_out),
+
+    /*
+     * Configuration
+     */
+    .prescale(prescale)
+);
+
+endmodule
+
+`resetall

tb/xfcp/taxi_xfcp_if_uart/xfcp.py

@@ -0,0 +1 @@
+../xfcp.py

tb/xfcp/xfcp.py

@@ -0,0 +1,159 @@
+# SPDX-License-Identifier: MIT
+"""
+
+Copyright (c) 2017-2025 FPGA Ninja, LLC
+
+Authors:
+- Alex Forencich
+
+"""
+
+import struct
+
+
+def cobs_encode(block):
+    block = bytes(block)
+    enc = bytearray()
+
+    seg = bytearray()
+    code = 1
+
+    new_data = True
+
+    for b in block:
+        if b == 0:
+            enc.append(code)
+            enc.extend(seg)
+            code = 1
+            seg = bytearray()
+            new_data = True
+        else:
+            code += 1
+            seg.append(b)
+            new_data = True
+            if code == 255:
+                enc.append(code)
+                enc.extend(seg)
+                code = 1
+                seg = bytearray()
+                new_data = False
+
+    if new_data:
+        enc.append(code)
+        enc.extend(seg)
+
+    return bytes(enc)
+
+
+def cobs_decode(block):
+    block = bytes(block)
+    dec = bytearray()
+
+    code = 0
+
+    i = 0
+
+    if 0 in block:
+        return None
+
+    while i < len(block):
+        code = block[i]
+        i += 1
+        if i+code-1 > len(block):
+            return None
+        dec.extend(block[i:i+code-1])
+        i += code-1
+        if code < 255 and i < len(block):
+            dec.append(0)
+
+    return bytes(dec)
+
+
+class XfcpFrame(object):
+    def __init__(self, payload=b'', path=[], rpath=[], ptype=0):
+        self._payload = b''
+        self.path = path
+        self.rpath = rpath
+        self.ptype = ptype
+
+        if type(payload) is bytes:
+            self.payload = payload
+        if type(payload) is XfcpFrame:
+            self.payload = payload.payload
+            self.path = list(payload.path)
+            self.rpath = list(payload.rpath)
+            self.ptype = payload.ptype
+
+    @property
+    def payload(self):
+        return self._payload
+
+    @payload.setter
+    def payload(self, value):
+        self._payload = bytes(value)
+
+    def build(self):
+        data = bytearray()
+
+        for p in self.path:
+            data.extend(struct.pack('B', p))
+
+        if self.rpath:
+            data.extend(struct.pack('B', 0xFE))
+            for p in self.rpath:
+                data.extend(struct.pack('B', p))
+
+        data.extend(struct.pack('B', 0xFF))
+
+        data.extend(struct.pack('B', self.ptype))
+
+        data.extend(self.payload)
+
+        return data
+
+    def build_cobs(self):
+        return cobs_encode(self.build())+b'\x00'
+
+    @classmethod
+    def parse(cls, data):
+        data = bytes(data)
+
+        i = 0
+
+        path = []
+        rpath = []
+
+        while i < len(data) and data[i] < 0xFE:
+            path.append(data[i])
+            i += 1
+
+        if data[i] == 0xFE:
+            i += 1
+            while i < len(data) and data[i] < 0xFE:
+                rpath.append(data[i])
+                i += 1
+
+        assert data[i] == 0xFF
+        i += 1
+
+        ptype = data[i]
+        i += 1
+
+        payload = data[i:]
+
+        return cls(payload, path, rpath, ptype)
+
+    @classmethod
+    def parse_cobs(cls, data):
+        return cls.parse(cobs_decode(bytes(data)))
+
+    def __eq__(self, other):
+        if type(other) is XfcpFrame:
+            return (self.path == other.path and
+                self.rpath == other.rpath and
+                self.ptype == other.ptype and
+                self.payload == other.payload)
+        return False
+
+    def __repr__(self):
+        return f"XfcpFrame(payload={self.payload!r}, path={self.path!r}, rpath={self.rpath!r}, ptype={self.ptype})"