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suservo: use 125 MHz SDR ADC 

* easier timing
* natural sampling on rising edge
* timing, signal robustness
* adjust the servo iteration timing
This commit is contained in:
Robert Jördens 2018-04-25 14:23:22 +00:00
parent 37c186a0fc
commit b44d6517d1
5 changed files with 28 additions and 40 deletions
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27
artiq/gateware/suservo/adc_ser.py
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@ -19,9 +19,9 @@ ADCParams = namedtuple("ADCParams", [
"t_cnvh", # CNVH duration (minimum)
"t_conv", # CONV duration (minimum)
"t_rtt", # upper estimate for clock round trip time from
# sck at the FPGA to clkout at the FPGA.
# sck at the FPGA to clkout at the FPGA (cycles)
# this avoids having synchronizers and another counter
# to signal end-of transfer (CLKOUT cycles)
# to signal end-of transfer
# and it ensures fixed latency early in the pipeline
])
@ -51,11 +51,11 @@ class ADC(Module):
assert p.lanes == len(sdo)
# set up counters for the four states CNVH, CONV, READ, RTT
t_read = p.width*p.channels//p.lanes//2 # DDR
assert 2*p.lanes*t_read == p.width*p.channels
t_read = p.width*p.channels//p.lanes # SDR
assert p.lanes*t_read == p.width*p.channels
assert all(_ > 0 for _ in (p.t_cnvh, p.t_conv, p.t_rtt))
assert p.t_conv > 1
count = Signal(max=max(p.t_cnvh, p.t_conv, t_read, p.t_rtt) - 1,
count = Signal(max=max(p.t_cnvh, p.t_conv - 1, t_read, p.t_rtt + 1) - 1,
reset_less=True)
count_load = Signal.like(count)
count_done = Signal()
@ -92,7 +92,7 @@ class ADC(Module):
)
fsm.act("READ",
self.reading.eq(1),
count_load.eq(p.t_rtt), # account for sck ODDR delay
count_load.eq(p.t_rtt), # again account for sck ODDR delay
pads.sck_en.eq(1),
If(count_done,
NextState("RTT")
@ -113,21 +113,20 @@ class ADC(Module):
self.clock_domains.cd_ret = ClockDomain("ret", reset_less=True)
self.comb += [
# falling clkout makes two bits available
self.cd_ret.clk.eq(~pads.clkout)
self.cd_ret.clk.eq(pads.clkout)
]
k = p.channels//p.lanes
assert 2*t_read == k*p.width
assert t_read == k*p.width
for i, sdo in enumerate(sdo):
sdo_sr0 = Signal(t_read - 1)
sdo_sr1 = Signal(t_read - 1)
sdo_sr = Signal(2*t_read)
self.sync.ret += [
If(self.reading & sck_en_ret,
sdo_sr0.eq(Cat(sdo[0], sdo_sr0)),
sdo_sr1.eq(Cat(sdo[1], sdo_sr1))
sdo_sr[1:].eq(sdo_sr),
sdo_sr[0].eq(sdo),
)
]
self.comb += [
Cat(reversed([self.data[i*k + j] for j in range(k)])).eq(
Cat(sdo, zip(sdo_sr0, sdo_sr1)))
Cat(reversed([self.data[i*k + j] for j in range(k)])
).eq(sdo_sr)
]

23
artiq/gateware/suservo/pads.py
View File

@ -22,7 +22,7 @@ class SamplerPads(Module):
self.specials += [
DifferentialOutput(self.cnv, cnv.p, cnv.n),
DifferentialOutput(1, sdr.p, sdr.n),
DDROutput(0, self.sck_en, sck),
DDROutput(self.sck_en, 0, sck),
DifferentialOutput(sck, spip.clk, spin.clk),
DifferentialInput(dp.clkout, dn.clkout, clkout_se),
Instance(
@ -43,8 +43,7 @@ class SamplerPads(Module):
# platform.add_period_constraint(sampler_pads.clkout_p, 8.)
for i in "abcd":
sdo_se = Signal()
sdo_d = Signal()
sdo = Signal(2)
sdo = Signal()
setattr(self, "sdo{}".format(i), sdo)
sdop = getattr(dp, "sdo{}".format(i))
sdon = getattr(dn, "sdo{}".format(i))
@ -53,24 +52,16 @@ class SamplerPads(Module):
Instance(
"IDELAYE2",
p_HIGH_PERFORMANCE_MODE="TRUE", p_IDELAY_TYPE="FIXED",
p_SIGNAL_PATTERN="DATA", p_IDELAY_VALUE=31,
p_SIGNAL_PATTERN="DATA", p_IDELAY_VALUE=15,
p_REFCLK_FREQUENCY=200.,
i_IDATAIN=sdo_se, o_DATAOUT=sdo_d),
Instance("IDDR",
p_DDR_CLK_EDGE="SAME_EDGE",
i_C=~self.clkout, i_CE=1, i_S=0, i_R=0,
i_D=sdo_d, o_Q1=sdo[0], o_Q2=sdo[1]) # sdo[1] older
i_IDATAIN=sdo_se, o_DATAOUT=sdo),
]
# 4, -0+1.5 hold (t_HSDO_DDR), -0.2+0.2 skew
# 8, -0+1.5 hold (t_HSDO_DDR), -0.5+0.5 skew
platform.add_platform_command(
"set_input_delay -clock {clk} "
"-max 1.6 [get_ports {port}]\n"
"-max 2 [get_ports {port}] -clock_fall\n"
"set_input_delay -clock {clk} "
"-min -0.1 [get_ports {port}]\n"
"set_input_delay -clock {clk} "
"-max 1.6 [get_ports {port}] -clock_fall -add_delay\n"
"set_input_delay -clock {clk} "
"-min -0.1 [get_ports {port}] -clock_fall -add_delay",
"-min -0.5 [get_ports {port}] -clock_fall",
clk=dp.clkout, port=sdop)

7
artiq/gateware/suservo/servo.py
View File

@ -16,14 +16,15 @@ class Servo(Module):
self.comb += j.eq(i), l.eq(k)
t_adc = (adc_p.t_cnvh + adc_p.t_conv + adc_p.t_rtt +
adc_p.channels*adc_p.width//2//adc_p.lanes) + 1
adc_p.channels*adc_p.width//adc_p.lanes) + 1
t_iir = ((1 + 4 + 1) << iir_p.channel) + 1
t_dds = (dds_p.width*2 + 1)*dds_p.clk + 1
t_cycle = max(t_adc, t_iir, t_dds)
assert t_iir + (2 << iir_p.channel) < t_cycle, "need shifting time"
self.start = Signal()
t_restart = t_cycle - t_iir - t_adc
t_restart = t_cycle - t_adc
assert t_restart > 0
cnt = Signal(max=t_restart)
cnt_done = Signal()
@ -39,7 +40,7 @@ class Servo(Module):
self.done.eq(self.dds.done),
]
self.sync += [
If(iir_done & ~cnt_done & ~token[0],
If(self.adc.done & ~cnt_done,
cnt.eq(cnt - 1),
),
If(self.adc.start,

7
artiq/gateware/test/suservo/test_adc.py
View File

@ -31,15 +31,15 @@ class TB(Module):
srs = []
for i in range(p.lanes):
name = "sdo" + string.ascii_lowercase[i]
sdo = Signal(2, name=name, reset_less=True)
sdo = Signal(name=name, reset_less=True)
self.sdo.append(sdo)
setattr(self, name, sdo)
sr = Signal(p.width*p.channels//p.lanes, reset_less=True)
srs.append(sr)
self.sync.adc += [
sdo.eq(Cat(self._dly(sr[-1], 3), self._dly(sr[-2], 3))),
sdo.eq(self._dly(sr[-1], -1)),
If(adc_sck_en,
sr[2:].eq(sr)
sr[1:].eq(sr)
)
]
cnv_old = Signal(reset_less=True)
@ -54,6 +54,7 @@ class TB(Module):
self.comb += [
adc_sck_en.eq(self._dly(self.sck_en, 1)),
self.sck_en_ret.eq(self._dly(adc_sck_en)),
adc_clk_rec.eq(self._dly(self.sck, 1)),
self.clkout.eq(self._dly(adc_clk_rec)),
]

4
artiq/gateware/test/suservo/test_servo.py
View File

@ -93,10 +93,6 @@ def main():
"adc": (8, 0),
"ret": (8, 0),
"async": (2, 0),
},
special_overrides={
io.DDROutput: test_adc.DDROutput,
io.DDRInput: test_adc.DDRInput
})