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DDMTD: replace first edge deglitcher with median edge deglitcher #293

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sb10q merged 1 commits from morgan/artiq-zynq:deglitcher into master 2024-04-29 13:05:02 +08:00
Conversation 0 Commits 1 Files Changed 1 +43 -17
1 changed files with 43 additions and 17 deletions
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58
src/gateware/ddmtd.py
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@ -25,25 +25,51 @@ class DDMTDSampler(Module):
]
class DDMTDDeglitcherFirstEdge(Module):
def __init__(self, input_signal, blind_period=400):
class DDMTDDeglitcherMedianEdge(Module):
def __init__(self, counter, input_signal, stable_0_period=100, stable_1_period=100):
self.tag = Signal(len(counter))
self.detect = Signal()
rising = Signal()
input_signal_r = Signal()
stable_0_counter = Signal(reset=stable_0_period - 1, max=stable_0_period)
stable_1_counter = Signal(reset=stable_1_period - 1, max=stable_1_period)
# # #
self.sync.helper += [
input_signal_r.eq(input_signal),
rising.eq(input_signal & ~input_signal_r)
]
# Based on CERN's median edge deglitcher FSM
# https://white-rabbit.web.cern.ch/documents/Precise_time_and_frequency_transfer_in_a_White_Rabbit_network.pdf (p.72)
fsm = ClockDomainsRenamer("helper")(FSM(reset_state="WAIT_STABLE_0"))
self.submodules += fsm
blind_counter = Signal(max=blind_period)
self.sync.helper += [
If(blind_counter != 0, blind_counter.eq(blind_counter - 1)),
If(input_signal_r, blind_counter.eq(blind_period - 1)),
self.detect.eq(rising & (blind_counter == 0))
]
fsm.act("WAIT_STABLE_0",
If(stable_0_counter != 0,
NextValue(stable_0_counter, stable_0_counter - 1)
).Else(
NextValue(stable_0_counter, stable_0_period - 1),
NextState("WAIT_EDGE")
),
If(input_signal,
NextValue(stable_0_counter, stable_0_period - 1)
),
)
fsm.act("WAIT_EDGE",
If(input_signal,
NextValue(self.tag, counter),
NextState("GOT_EDGE")
)
)
fsm.act("GOT_EDGE",
If(stable_1_counter != 0,
NextValue(stable_1_counter, stable_1_counter - 1)
).Else(
NextValue(stable_1_counter, stable_1_period - 1),
self.detect.eq(1),
NextState("WAIT_STABLE_0")
),
If(~input_signal,
NextValue(self.tag, self.tag + 1),
NextValue(stable_1_counter, stable_1_period - 1)
),
)
class DDMTD(Module):
@ -55,13 +81,13 @@ class DDMTD(Module):
# # #
deglitcher = DDMTDDeglitcherFirstEdge(input_signal)
deglitcher = DDMTDDeglitcherMedianEdge(counter, input_signal)
self.submodules += deglitcher
self.sync.helper += [
self.h_tag_update.eq(0),
If(deglitcher.detect,
self.h_tag_update.eq(1),
self.h_tag.eq(counter)
self.h_tag.eq(deglitcher.tag)
)
]