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atusb/fw3/an/: USB debugging scripts

This commit is contained in:
Werner Almesberger 2011-02-13 23:00:35 -03:00
parent c1dc00ee44
commit f4d299d22b
4 changed files with 195 additions and 0 deletions

25
atusb/fw3/an/README Normal file
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workflow:
- connect zprobe (note: it currently inverts because it didn't have any
other chips around. this may change later.)
- capture the USB signals at an interesting moment with a sample rate of
50 MSa/s
- zoom into the frame(s) of interest
- download the data with
./get.py
- decode with
./dec.py
For manual decoding, set the coders to D+ and D- (we need D- for SE0
and SE1 detection), then click on a rising clock edge left of the
packet and move the cursor to the right.
- if there are problems with the clock, the analog signal and digital
signals derived from it can be examined after running dec.py with
./plot
(Note that the digital zprobe hides any analog anomalies.)

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atusb/fw3/an/dec.py Executable file
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#!/usr/bin/python
from tmc.wave import *
from tmc.dxplore import dxplore
from tmc.decode import d_usb_stream
#
# Clock recovery: we assume that each change in the wave is triggered by a
# clock edge. We know the clock's nominal period and resynchronize on each
# edge. Additionally, we can obtain a list of times when a timing violation
# has occurred.
#
# Note that the timing violations logic doesn't make much sense in its present
# form, since it mainly measures noise (particularly if we're digitizing slow
# edges) and not clock drift.
#
# A more useful metric would be accumulated error from some point of reference
# or at least the timing of same edges, to eliminate (generally harmless) time
# offsets introduced by digitizing.
#
# So it would probably make more sense for "recover" not to check for timing
# violations at all, and leave this to more specialized functions.
#
def recover(self, period, min = None, max = None, t0 = None):
if t0 is None:
t0 = self.data[0]
v = not self.initial
res = []
violations = []
for t in self.data:
v = not v
if t <= t0:
continue
n = 0
while t0 < t-period/2:
res.append(t0)
t0 += period
n += 1
if min is not None:
if t0-t > n*min:
violations.append(t)
if max is not None:
if t-t0 > n*max:
violations.append(t)
t0 = t
return res, violations
#
# Load the analog waves saved by get.py
#
wv = waves()
wv.load("_wv")
#
# Digitize the waves and save the result.
#
dp = wv[0].digitize(1.5, 1.8)
dm = wv[1].digitize(1.5, 1.8)
wv = waves(dp, dm, dp-dm)
wv.save("_dig")
#
# Also record the differential signal.
#
wd = wv[1]-wv[0]
dd = wd.digitize(-0.5, 0.5)
wd.save("_diff")
#
# Run clock recovery on D+/D-. We only need one, but check both to be sure.
#
#p = 1/1.5e6
p = 1/12e6
dp_t, viol = recover(dp, p, p*0.9, p*1.1)
print viol
dm_t, viol = recover(dm, p, p*.9, p*1.1, t0 = dp.data[0])
print viol
#
# Shift the clock by half a period, add a few periods to get steady state and
# SE0s (if any), and then sample the data lines.
#
clk = map(lambda t: t+p/2, dp_t)
clk.extend((clk[-1]+p, clk[-1]+2*p, clk[-1]+3*p))
dp_bv = dp.get(clk)
dm_bv = dm.get(clk)
#
# Save a wave with the recovered clock to make it easier to find the bits in
# analog graphs.
#
dd.data = dp_t;
dd.save("_clk")
#
# For decoding, we need a fake bit clock. We generate it by doubling each data
# bit and generating a L->H transition during this bit.
#
dpd = []
dmd = []
dck = []
# err, silly, seems that we've mixed up D+ and D- all over the place :-)
print d_usb_stream(dm_bv[:], dp_bv[:])
for v in dp_bv:
dpd.append(v)
dpd.append(v)
dck.append(0)
dck.append(1)
for v in dm_bv:
dmd.append(v)
dmd.append(v)
#
# Display the reconstructed digital signal. Note that the absolute time is only
# correct at the beginning and that relative time is only accurate over
# intervals in which no significant clock resynchronization has occurred.
#
# In fact, dxplore should probably have an option to either turn off time
# entirely or to display a user-provided time axis. The latter may be a bit
# tricky to implement.
#
dxplore((dmd, dpd, dck), 0, p/2, labels = ("D+", "D-", "CLK"))

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atusb/fw3/an/get.py Executable file
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#!/usr/bin/python
from tmc.scope import rigol_ds1000c
#-800, +1600
s = rigol_ds1000c()
#s.debug = False
pos = s.hor.pos
scale = s.hor.scale
t0 = pos-scale*s.div_hor/2
t1 = pos+scale*s.div_hor/2
print t0, t1
#zoom = 10
#step = scale/s.samples_per_div/zoom
#print step
step = 4e-9
step = 2e-9
w = s.wave((s.ch[0], s.ch[1]), start = t0, end = t1, step = step)
w[0] = 3.3-w[0]
w[1] = 3.3-w[1]
s.hor.pos = pos
s.hor.scale = scale
w[0].label = "D+";
w[1].label = "D-";
w.save("_wv")

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atusb/fw3/an/plot Executable file
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#!/bin/sh
#
# Plot output of "dec"
#
gnuplot -persist <<EOF
set style data lines
plot "_wv" using 1:(\$2-4), \
"_dig" using 1:(\$2*3.3-4) lw 2, \
"_wv" using 1:3, \
"_dig" using 1:(\$3*3.3) lw 2, \
"_clk" using 1:(\$2+1) lt 7
EOF