## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
##
-# USB (full-speed) protocol decoder
+# USB (low-speed and full-speed) protocol decoder
import sigrokdecode as srd
-# Symbols (used as states of our state machine, too)
+# Full-speed symbols (used as states of our state machine, too).
+# Note: Low-speed J and K are inverted compared to the full-speed J and K!
syms = {
+ # (<dp>, <dm>): <symbol/state>
(0, 0): 'SE0',
(1, 0): 'J',
(0, 1): 'K',
(1, 1): 'SE1',
}
-# ...
+# Packet IDs
pids = {
'10000111': 'OUT', # Tokens
'10010110': 'IN',
'01101001': 'NYET',
}
+def get_sym(signalling, dp, dm):
+ # Note: Low-speed J and K are inverted compared to the full-speed J and K!
+ if signalling == 'low-speed':
+ s = syms[dp, dm]
+ if s == 'J':
+ return 'K'
+ elif s == 'K':
+ return 'J'
+ else:
+ return s
+ elif signalling == 'full-speed':
+ return syms[dp, dm]
+
def bitstr_to_num(bitstr):
if not bitstr:
return 0
dev = bitstr_to_num(data[:7])
ep = bitstr_to_num(data[7:])
data = 'DEV %d EP %d' % (dev, ep)
-
elif pid in ('DATA0', 'DATA1'):
data = packet[16:-16]
tmp = ''
else:
data = packet[16:]
+ # The SYNC pattern for low-speed/full-speed is KJKJKJKK (0001).
if sync != '00000001':
return 'SYNC INVALID!'
api_version = 1
id = 'usb'
name = 'USB'
- longname = 'Universal Serial Bus'
- desc = 'Universal Serial Bus'
+ longname = 'Universal Serial Bus (LS/FS)'
+ desc = 'USB 1.x (low-speed and full-speed) serial protocol.'
license = 'gplv2+'
inputs = ['logic']
outputs = ['usb']
{'id': 'dm', 'name': 'D-', 'desc': 'USB D- signal'},
]
optional_probes = []
- options = {}
+ options = {
+ 'signalling': ['Signalling', 'full-speed'],
+ }
annotations = [
['Text', 'Human-readable text']
]
def __init__(self):
- pass
+ self.sym = 'J'
+ self.samplenum = 0
+ self.scount = 0
+ self.packet = ''
def start(self, metadata):
self.samplerate = metadata['samplerate']
# self.out_proto = self.add(srd.OUTPUT_PROTO, 'usb')
self.out_ann = self.add(srd.OUTPUT_ANN, 'usb')
- if self.samplerate < 48000000:
- raise Exception('Samplerate (%d) not sufficient for USB '
- 'decoding, need at least 48MHz' % self.samplerate)
-
- # Initialise decoder state.
- self.sym = 'J'
- self.samplenum = 0
- self.packet = ''
-
def report(self):
pass
def decode(self, ss, es, data):
- for (self.samplenum, (dm, dp)) in data:
+ for (self.samplenum, (dp, dm)) in data:
+
+ # Note: self.samplenum is the absolute sample number, whereas
+ # self.scount only counts the number of samples since the
+ # last change in the D+/D- lines.
+ self.scount += 1
- sym = syms[dp, dm]
+ sym = get_sym(self.options['signalling'], dp, dm)
- # ...
+ # Wait for a symbol change (i.e., change in D+/D- lines).
if sym == self.sym:
continue
- if self.samplenum == 1:
- # We ignore single sample width pulses.
- # I sometimes get these with the OLS.
+ if self.scount == 1:
+ # We ignore single sample width "pulses", i.e., symbol changes
+ # (D+/D- line changes). I sometimes get these with the OLS.
self.sym = sym
- self.samplenum = 0
+ self.scount = 0
continue
# How many bits since the last transition?
if self.packet != '' or self.sym != 'J':
- bitcount = int((self.samplenum - 1) * 12000000 / self.samplerate)
+ if self.options['signalling'] == 'low-speed':
+ bitrate = 1500000 # 1.5Mb/s (+/- 1.5%)
+ elif self.options['signalling'] == 'full-speed':
+ bitrate = 12000000 # 12Mb/s (+/- 0.25%)
+ bitcount = int((self.scount - 1) * bitrate / self.samplerate)
else:
bitcount = 0
else:
# Longer than EOP, assume reset.
self.put(0, 0, self.out_ann, [0, ['RESET']])
- self.samplenum = 0
+ self.scount = 0
self.sym = sym
self.packet = ''
continue
elif bitcount > 6:
self.put(0, 0, self.out_ann, [0, ['BIT STUFF ERROR']])
- self.samplenum = 0
+ self.scount = 0
self.sym = sym