103 lines
3.2 KiB
Python
103 lines
3.2 KiB
Python
# SPDX-License-Identifier: AGPL-3.0-Only
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# Copyright (C) 2022 Sean Anderson <seanga2@gmail.com>
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import random
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from statistics import NormalDist
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import cocotb
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from cocotb.binary import BinaryValue
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from cocotb.clock import Clock
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from cocotb.regression import TestFactory
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from cocotb.triggers import RisingEdge, Timer
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from .util import compare_lists, print_list_at, timeout
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BITS = 1000
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def random_delays(count):
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# Target BER is 1e9 and the maximum jitter is 1.4ns
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# This is just random jitter (not DDJ or DCJ) but it'll do
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delay_dist = NormalDist(8000, 1400 / NormalDist().inv_cdf(1-2e-9))
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return (int(delay) for delay in delay_dist.samples(count))
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def mindelays(count):
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return (7900,) * count
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def maxdelays(count):
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return (8100,) * count
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async def check_bits(pmd, ins):
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# Wait for things to stabilize
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await RisingEdge(pmd.signal_status)
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outs = []
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while pmd.signal_status.value:
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await RisingEdge(pmd.clk_125)
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valid = pmd.rx_data_valid.value
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if valid == 0:
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pass
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elif valid == 1:
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outs.append(pmd.rx_data[1].value)
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else:
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outs.append(pmd.rx_data[1].value)
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outs.append(pmd.rx_data[0].value)
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best_corr = -1
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best_off = None
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for off in range(16):
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corr = sum(i == o for i, o in zip(ins[off:], outs))
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if corr > best_corr:
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best_corr = corr
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best_off = off
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print(f"best offset is {best_off} correlation {best_corr/(len(ins) - best_off)}")
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compare_lists(ins[best_off:], outs)
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# There will be a few bits at the end not recorded because signal_detect
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# isn't delayed like the data signals
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print(best_corr, len(ins), best_off)
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assert best_corr > len(ins) - best_off - 10
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@timeout(100, 'us')
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async def test_rx(pmd, delays):
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pmd.signal_detect.value = 0
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await Timer(1)
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await cocotb.start(Clock(pmd.clk_125, 8, units='ns').start())
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# random phase
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await Timer(random.randrange(1, 8000), units='ps')
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await cocotb.start(Clock(pmd.clk_250, 4, units='ns').start())
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ins = [random.randrange(2) for _ in range(BITS)]
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async def generate_bits():
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# random phase
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await Timer(random.randrange(1, 8000), units='ps')
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pmd.signal_detect.value = 1
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last_bit = ins[0]
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running_disparity = 0
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for i, delay in zip(ins, delays(len(ins))):
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pmd.indicate_data.value = i
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# Keep track of how far off we are...
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if i != last_bit:
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running_disparity = 0
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running_disparity += 8000 - delay
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last_bit = i
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# If we get more than a quarter cycle off, use perfect delay until
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# we get a transition
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if abs(running_disparity) >= 2000:
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running_disparity -= 8000 - delay
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delay = 8000
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try:
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pmd.delay.value = delay
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except AttributeError:
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pass
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await Timer(delay, units='ps')
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pmd.signal_detect.value = 0
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await cocotb.start(generate_bits())
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await check_bits(pmd, ins)
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rx_tests = TestFactory(test_rx)
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rx_tests.add_option('delays', (random_delays, mindelays, maxdelays))
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rx_tests.generate_tests()
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