65 lines
2.3 KiB
Python
65 lines
2.3 KiB
Python
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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.triggers import RisingEdge, Timer
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@cocotb.test(timeout_time=100, timeout_unit='us')
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async def test_rx(pmd):
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pmd.rx.value = BinaryValue('X')
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await cocotb.start(Clock(pmd.rx_clk_125, 8, units='ns').start())
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# random phase
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await Timer(random.randrange(0, 8000), units='ps')
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await cocotb.start(Clock(pmd.rx_clk_250, 4, units='ns').start())
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ins = [random.randrange(2) for _ in range(1000)]
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async def generate_bits():
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# random phase
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await Timer(random.randrange(0, 8000), units='ps')
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pmd.signal_detect.value = 1
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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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for i, delay in zip(ins, (int(delay) for delay in delay_dist.samples(len(ins)))):
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pmd.rx.value = i
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pmd.delay.value = delay
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await Timer(delay, units='ps')
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#await Timer(8100, units='ps')
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pmd.signal_detect.value = 0
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await cocotb.start(generate_bits())
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# Wait for things to stabilize
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await RisingEdge(pmd.valid)
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outs = []
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while pmd.signal_status.value:
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await RisingEdge(pmd.rx_clk_125)
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valid = pmd.pmd_data_rx_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.pmd_data_rx[1].value)
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else:
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outs.append(pmd.pmd_data_rx[1].value)
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outs.append(pmd.pmd_data_rx[0].value)
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best_corr = -1
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best_off = None
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for off in range(-7, 8):
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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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for idx, (i, o) in enumerate(zip(ins[best_off:], outs)):
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if i != o:
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print(idx)
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print(*ins[idx+best_off-50:idx+best_off+50], sep='')
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print(*outs[idx-50:idx+50], sep='')
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assert False
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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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assert best_corr > len(ins) - best_off - 10
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