2 ## This file is part of the sigrok project.
4 ## Copyright (C) 2010 Uwe Hermann <uwe@hermann-uwe.de>
6 ## This program is free software; you can redistribute it and/or modify
7 ## it under the terms of the GNU General Public License as published by
8 ## the Free Software Foundation; either version 2 of the License, or
9 ## (at your option) any later version.
11 ## This program is distributed in the hope that it will be useful,
12 ## but WITHOUT ANY WARRANTY; without even the implied warranty of
13 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 ## GNU General Public License for more details.
16 ## You should have received a copy of the GNU General Public License
17 ## along with this program; if not, write to the Free Software
18 ## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
22 # I2C protocol decoder
26 # The Inter-Integrated Circuit (I2C) bus is a bidirectional, multi-master
27 # bus using two signals (SCL = serial clock line, SDA = serial data line).
29 # There can be many devices on the same bus. Each device can potentially be
30 # master or slave (and that can change during runtime). Both slave and master
31 # can potentially play the transmitter or receiver role (this can also
34 # Possible maximum data rates:
35 # - Standard mode: 100 kbit/s
36 # - Fast mode: 400 kbit/s
37 # - Fast-mode Plus: 1 Mbit/s
38 # - High-speed mode: 3.4 Mbit/s
40 # START condition (S): SDA = falling, SCL = high
41 # Repeated START condition (Sr): same as S
42 # STOP condition (P): SDA = rising, SCL = high
44 # All data bytes on SDA are exactly 8 bits long (transmitted MSB-first).
45 # Each byte has to be followed by a 9th ACK/NACK bit. If that bit is low,
46 # that indicates an ACK, if it's high that indicates a NACK.
48 # After the first START condition, a master sends the device address of the
49 # slave it wants to talk to. Slave addresses are 7 bits long (MSB-first).
50 # After those 7 bits, a data direction bit is sent. If the bit is low that
51 # indicates a WRITE operation, if it's high that indicates a READ operation.
53 # Later an optional 10bit slave addressing scheme was added.
56 # http://www.nxp.com/acrobat/literature/9398/39340011.pdf (v2.1 spec)
57 # http://www.nxp.com/acrobat/usermanuals/UM10204_3.pdf (v3 spec)
58 # http://en.wikipedia.org/wiki/I2C
61 # TODO: Look into arbitration, collision detection, clock synchronisation, etc.
62 # TODO: Handle clock stretching.
63 # TODO: Handle combined messages / repeated START.
64 # TODO: Implement support for 7bit and 10bit slave addresses.
65 # TODO: Implement support for inverting SDA/SCL levels (0->1 and 1->0).
66 # TODO: Implement support for detecting various bus errors.
71 # The output consists of a (Python) list of I2C "packets", each of which
72 # has an (implicit) index number (its index in the list).
73 # Each packet consists of a Python dict with certain key/value pairs.
75 # TODO: Make this a list later instead of a dict?
78 # - 'S' (START condition)
79 # - 'Sr' (Repeated START)
80 # - 'AR' (Address, read)
81 # - 'AW' (Address, write)
83 # - 'DW' (Data, write)
84 # - 'P' (STOP condition)
85 # 'range': (tuple of 2 integers, the min/max samplenumber of this range)
87 # - min/max can also be identical.
88 # 'data': (actual data as integer ???) TODO: This can be very variable...
89 # 'ann': (string; additional annotations / comments)
92 # [{'type': 'S', 'range': (150, 160), 'data': None, 'ann': 'Foobar'},
93 # {'type': 'AW', 'range': (200, 300), 'data': 0x50, 'ann': 'Slave 4'},
94 # {'type': 'DW', 'range': (310, 370), 'data': 0x00, 'ann': 'Init cmd'},
95 # {'type': 'AR', 'range': (500, 560), 'data': 0x50, 'ann': 'Get stat'},
96 # {'type': 'DR', 'range': (580, 640), 'data': 0xfe, 'ann': 'OK'},
97 # {'type': 'P', 'range': (650, 660), 'data': None, 'ann': None}]
99 # Possible other events:
100 # - Error event in case protocol looks broken:
101 # [{'type': 'ERROR', 'range': (min, max),
102 # 'data': TODO, 'ann': 'This is not a Microchip 24XX64 EEPROM'},
103 # [{'type': 'ERROR', 'range': (min, max),
104 # 'data': TODO, 'ann': 'TODO'},
105 # - TODO: Make list of possible errors accessible as metadata?
107 # TODO: I2C address of slaves.
108 # TODO: Handle multiple different I2C devices on same bus
109 # -> we need to decode multiple protocols at the same time.
110 # TODO: range: Always contiguous? Splitted ranges? Multiple per event?
117 # [[id, channel, description], ...] # TODO
120 # {'id': 'SCL', 'ch': 5, 'desc': 'Serial clock line'}
121 # {'id': 'SDA', 'ch': 7, 'desc': 'Serial data line'}
125 # 'signals': [{'SCL': }]}
129 """I2C protocol decoder"""
131 # FIXME: Get the data in the correct format in the first place.
132 inbuf = [ord(x) for x in inbuf]
134 # FIXME: This should be passed in as metadata, not hardcoded here.
138 'scl': {'ch': 5, 'name': 'SCL', 'desc': 'Serial clock line'},
139 'sda': {'ch': 7, 'name': 'SDA', 'desc': 'Serial data line'},
146 wr = startsample = -1
147 IDLE, START, ADDRESS, DATA = range(4)
150 # Get the channel/probe number of the SCL/SDA signals.
151 scl_bit = metadata['signals']['scl']['ch']
152 sda_bit = metadata['signals']['sda']['ch']
154 # Get SCL/SDA bit values (0/1 for low/high) of the first sample.
156 oldscl = (s & (1 << scl_bit)) >> scl_bit
157 oldsda = (s & (1 << sda_bit)) >> sda_bit
159 # Loop over all samples.
160 # TODO: Handle LAs with more/less than 8 channels.
161 for samplenum, s in enumerate(inbuf[1:]): # We skip the first byte...
162 # Get SCL/SDA bit values (0/1 for low/high).
163 scl = (s & (1 << scl_bit)) >> scl_bit
164 sda = (s & (1 << sda_bit)) >> sda_bit
166 # TODO: Wait until the bus is idle (SDA = SCL = 1) first?
168 # START condition (S): SDA = falling, SCL = high
169 if (oldsda == 1 and sda == 0) and scl == 1:
170 o = {'type': 'S', 'range': (samplenum, samplenum),
171 'data': None, 'ann': None},
176 # Data latching by transmitter: SCL = low
180 # Data sampling of receiver: SCL = rising
181 elif (oldscl == 0 and scl == 1):
182 if startsample == -1:
183 startsample = samplenum
186 # out.append("%d\t\tRECEIVED BIT %d: %d\n" % \
187 # (samplenum, 8 - bitcount, sda))
189 # Address and data are transmitted MSB-first.
196 # We received 8 address/data bits and the ACK/NACK bit.
197 data >>= 1 # Shift out unwanted ACK/NACK bit here.
198 ack = (sda == 1) and 'N' or 'A'
199 d = (state == ADDRESS) and (data & 0xfe) or data
201 wr = (data & 1) and 1 or 0
204 'range': (startsample, samplenum - 1),
205 'data': d, 'ann': None}
206 if state == ADDRESS and wr == 1:
208 elif state == ADDRESS and wr == 0:
210 elif state == DATA and wr == 1:
212 elif state == DATA and wr == 0:
215 o = {'type': ack, 'range': (samplenum, samplenum),
216 'data': None, 'ann': None}
218 bitcount = data = startsample = 0
221 # STOP condition (P): SDA = rising, SCL = high
222 elif (oldsda == 0 and sda == 1) and scl == 1:
223 o = {'type': 'P', 'range': (samplenum, samplenum),
224 'data': None, 'ann': None},
229 # Save current SDA/SCL values for the next round.
233 # FIXME: Just for testing...
240 'longname': 'Inter-Integrated Circuit (I2C) bus',
241 'desc': 'I2C is a two-wire, multi-master, serial bus.',
243 'author': 'Uwe Hermann',
244 'email': 'uwe@hermann-uwe.de',
249 ['scl', 'Serial clock line'],
250 ['sda', 'Serial data line'],
253 'address-space': ['Address space (in bits)', 7],
259 # Use psyco (if available) as it results in huge performance improvements.