## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
##
-#
-# USB Full-speed protocol decoder
-#
-# Full-speed USB signalling consists of two signal lines, both driven at 3.3V
-# logic levels. The signals are DP (D+) and DM (D-), and normally operate in
-# differential mode.
-# The state where DP=1,DM=0 is J, the state DP=0,DM=1 is K.
-# A state SE0 is defined where DP=DM=0. This common mode signal is used to
-# signal a reset or end of packet.
-#
-# Data transmitted on the USB is encoded with NRZI. A transition from J to K
-# or vice-versa indicates a logic 0, while no transition indicates a logic 1.
-# If 6 ones are transmitted consecutively, a zero is inserted to force a
-# transition. This is known as bit stuffing. Data is transferred at a rate
-# of 12Mbit/s. The SE0 transmitted to signal an end-of-packet is two bit
-# intervals long.
-#
-# Details:
-# https://en.wikipedia.org/wiki/USB
-# http://www.usb.org/developers/docs/
-#
+# USB (low-speed and full-speed) protocol decoder
import sigrokdecode as srd
-# States
-SE0, J, K, SE1 = 0, 1, 2, 3
-
-# ...
+# 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 = {
- (0, 0): SE0,
- (1, 0): J,
- (0, 1): K,
- (1, 1): SE1,
+ # (<dp>, <dm>): <symbol/state>
+ (0, 0): 'SE0',
+ (1, 0): 'J',
+ (0, 1): 'K',
+ (1, 1): 'SE1',
}
-# ...
+# Packet IDs (PIDs).
+# The first 4 bits are the 'packet type' field, the last 4 bits are the
+# 'check field' (each bit in the check field must be the inverse of the resp.
+# bit in the 'packet type' field; if not, that's a 'PID error').
+# For the 4-bit strings, the left-most '1' or '0' is the LSB, i.e. it's sent
+# to the bus first.
pids = {
- '10000111': 'OUT', # Tokens
- '10010110': 'IN',
- '10100101': 'SOF',
- '10110100': 'SETUP',
- '11000011': 'DATA0', # Data
- '11010010': 'DATA1',
- '01001011': 'ACK', # Handshake
- '01011010': 'NAK',
- '01111000': 'STALL',
- '01101001': 'NYET',
+ # Tokens
+ '10000111': ['OUT', 'Address & EP number in host-to-function transaction'],
+ '10010110': ['IN', 'Address & EP number in function-to-host transaction'],
+ '10100101': ['SOF', 'Start-Of-Frame marker & frame number'],
+ '10110100': ['SETUP', 'Address & EP number in host-to-function transaction for SETUP to a control pipe'],
+
+ # Data
+ # Note: DATA2 and MDATA are HS-only.
+ '11000011': ['DATA0', 'Data packet PID even'],
+ '11010010': ['DATA1', 'Data packet PID odd'],
+ '11100001': ['DATA2', 'Data packet PID HS, high bandwidth isosynchronous transaction in a microframe'],
+ '11110000': ['MDATA', 'Data packet PID HS for split and high-bandwidth isosynchronous transactions'],
+
+ # Handshake
+ '01001011': ['ACK', 'Receiver accepts error-free packet'],
+ '01011010': ['NAK', 'Receiver cannot accept or transmitter cannot send'],
+ '01111000': ['STALL', 'EP halted or control pipe request unsupported'],
+ '01101001': ['NYET', 'No response yet from receiver'],
+
+ # Special
+ '00111100': ['PRE', 'Host-issued preamble; enables downstream bus traffic to low-speed devices'],
+ '00111100': ['ERR', 'Split transaction error handshake'],
+ '00011110': ['SPLIT', 'HS split transaction token'],
+ '00101101': ['PING', 'HS flow control probe for a bulk/control EP'],
+ '00001111': ['Reserved', 'Reserved PID'],
}
+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
def packet_decode(packet):
sync = packet[:8]
pid = packet[8:16]
- pid = pids.get(pid, pid)
+ pid = pids.get(pid, (pid, ''))[0]
# Remove CRC.
if pid in ('OUT', 'IN', 'SOF', 'SETUP'):
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'
- longdesc = '...longdesc...'
+ longname = 'Universal Serial Bus (LS/FS)'
+ desc = 'USB 1.x (low-speed and full-speed) serial protocol.'
license = 'gplv2+'
inputs = ['logic']
outputs = ['usb']
{'id': 'dp', 'name': 'D+', 'desc': 'USB D+ signal'},
{'id': 'dm', 'name': 'D-', 'desc': 'USB D- signal'},
]
- extra_probes = []
- options = {}
+ optional_probes = []
+ options = {
+ 'signalling': ['Signalling', 'full-speed'],
+ }
annotations = [
- ['TODO', 'TODO']
+ ['Text', 'Human-readable text']
]
def __init__(self):
- pass
+ self.sym = 'J'
+ self.samplenum = 0
+ self.scount = 0
+ self.packet = ''
def start(self, metadata):
- self.rate = metadata['samplerate']
+ self.samplerate = metadata['samplerate']
# self.out_proto = self.add(srd.OUTPUT_PROTO, 'usb')
self.out_ann = self.add(srd.OUTPUT_ANN, 'usb')
- if self.rate < 48000000:
- raise Exception('Sample rate (%d) not sufficient for USB '
- 'decoding, need at least 48MHz' % self.rate)
-
- # Initialise decoder state.
- self.sym = J
- self.scount = 0
- self.packet = ''
-
def report(self):
pass
def decode(self, ss, es, data):
- for (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.scount == 1:
- # We ignore single sample width pulses.
- # I sometimes get these with the OLS.
+ # 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.scount = 0
continue
# How many bits since the last transition?
- if self.packet != '' or self.sym != J:
- bitcount = int((self.scount - 1) * 12000000 / self.rate)
+ if self.packet != '' or self.sym != 'J':
+ 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
- if self.sym == SE0:
+ if self.sym == 'SE0':
if bitcount == 1:
# End-Of-Packet (EOP)
self.put(0, 0, self.out_ann,
self.packet += '1' * bitcount
# Handle bit stuffing.
- if bitcount < 6 and sym != SE0:
+ if bitcount < 6 and sym != 'SE0':
self.packet += '0'
elif bitcount > 6:
self.put(0, 0, self.out_ann, [0, ['BIT STUFF ERROR']])
projects / libsigrokdecode.git / blobdiff