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1 | ## | |
2 | ## This file is part of the sigrok project. | |
3 | ## | |
4 | ## Copyright (C) 2010 Uwe Hermann <uwe@hermann-uwe.de> | |
5 | ## | |
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. | |
10 | ## | |
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. | |
15 | ## | |
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 | |
19 | ## | |
20 | ||
21 | # | |
22 | # I2C protocol decoder | |
23 | # | |
24 | ||
25 | # | |
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). | |
28 | # | |
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 | |
32 | # change at runtime). | |
33 | # | |
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 | |
39 | # | |
40 | # START condition (S): SDA = falling, SCL = high | |
41 | # Repeated START condition (Sr): same as S | |
42 | # STOP condition (P): SDA = rising, SCL = high | |
43 | # | |
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. | |
47 | # | |
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. | |
52 | # | |
53 | # Later an optional 10bit slave addressing scheme was added. | |
54 | # | |
55 | # Documentation: | |
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 | |
59 | # | |
60 | ||
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. | |
67 | ||
68 | # | |
69 | # I2C output format: | |
70 | # | |
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. | |
74 | # | |
75 | # TODO: Make this a list later instead of a dict? | |
76 | # | |
77 | # 'type': (string) | |
78 | # - 'S' (START condition) | |
79 | # - 'Sr' (Repeated START) | |
80 | # - 'AR' (Address, read) | |
81 | # - 'AW' (Address, write) | |
82 | # - 'DR' (Data, read) | |
83 | # - 'DW' (Data, write) | |
84 | # - 'P' (STOP condition) | |
85 | # 'range': (tuple of 2 integers, the min/max samplenumber of this range) | |
86 | # - (min, max) | |
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) | |
90 | # | |
91 | # Example output: | |
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}] | |
98 | # | |
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? | |
106 | # | |
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? | |
111 | # | |
112 | ||
113 | # | |
114 | # I2C input format: | |
115 | # | |
116 | # signals: | |
117 | # [[id, channel, description], ...] # TODO | |
118 | # | |
119 | # Example: | |
120 | # {'id': 'SCL', 'ch': 5, 'desc': 'Serial clock line'} | |
121 | # {'id': 'SDA', 'ch': 7, 'desc': 'Serial data line'} | |
122 | # ... | |
123 | # | |
124 | # {'inbuf': [...], | |
125 | # 'signals': [{'SCL': }]} | |
126 | # | |
127 | ||
128 | def decode(inbuf): | |
129 | """I2C protocol decoder""" | |
130 | ||
131 | # FIXME: Get the data in the correct format in the first place. | |
132 | inbuf = [ord(x) for x in inbuf] | |
133 | ||
134 | # FIXME: This should be passed in as metadata, not hardcoded here. | |
135 | metadata = { | |
136 | 'numchannels': 8, | |
137 | 'signals': { | |
138 | 'scl': {'ch': 5, 'name': 'SCL', 'desc': 'Serial clock line'}, | |
139 | 'sda': {'ch': 7, 'name': 'SDA' 'desc': 'Serial data line'}, | |
140 | }, | |
141 | } | |
142 | ||
143 | o = wr = ack = d = '' | |
144 | bitcount = data = 0 | |
145 | IDLE, START, ADDRESS, DATA = range(4) | |
146 | state = IDLE | |
147 | ||
148 | # Get the channel/probe number of the SCL/SDA signals. | |
149 | scl_bit = metadata['signals']['scl']['ch'] | |
150 | sda_bit = metadata['signals']['sda']['ch'] | |
151 | ||
152 | # Get SCL/SDA bit values (0/1 for low/high) of the first sample. | |
153 | s = inbuf[0] | |
154 | oldscl = (s & (1 << scl_bit)) >> scl_bit | |
155 | oldsda = (s & (1 << sda_bit)) >> sda_bit | |
156 | ||
157 | # Loop over all samples. | |
158 | # TODO: Handle LAs with more/less than 8 channels. | |
159 | for samplenum, s in enumerate(inbuf[1:]): # We skip the first byte... | |
160 | # Get SCL/SDA bit values (0/1 for low/high). | |
161 | scl = (s & (1 << scl_bit)) >> scl_bit | |
162 | sda = (s & (1 << sda_bit)) >> sda_bit | |
163 | ||
164 | # TODO: Wait until the bus is idle (SDA = SCL = 1) first? | |
165 | ||
166 | # START condition (S): SDA = falling, SCL = high | |
167 | if (oldsda == 1 and sda == 0) and scl == 1: | |
168 | o += "%d\t\tSTART\n" % samplenum | |
169 | state = ADDRESS | |
170 | bitcount = data = 0 | |
171 | ||
172 | # Data latching by transmitter: SCL = low | |
173 | elif (scl == 0): | |
174 | pass # TODO | |
175 | ||
176 | # Data sampling of receiver: SCL = rising | |
177 | elif (oldscl == 0 and scl == 1): | |
178 | bitcount += 1 | |
179 | ||
180 | # o += "%d\t\tRECEIVED BIT %d: %d\n" % \ | |
181 | # (samplenum, 8 - bitcount, sda) | |
182 | ||
183 | # Address and data are transmitted MSB-first. | |
184 | data <<= 1 | |
185 | data |= sda | |
186 | ||
187 | if bitcount != 9: | |
188 | continue | |
189 | ||
190 | # We received 8 address/data bits and the ACK/NACK bit. | |
191 | data >>= 1 # Shift out unwanted ACK/NACK bit here. | |
192 | # o += "%d\t\t%s: " % (samplenum, state) | |
193 | o += "%d\t\tTODO:STATE: " % samplenum | |
194 | ack = (sda == 1) and 'NACK' or 'ACK' | |
195 | d = (state == ADDRESS) and (data & 0xfe) or data | |
196 | wr = '' | |
197 | if state == ADDRESS: | |
198 | wr = (data & 1) and ' (W)' or ' (R)' | |
199 | state = DATA | |
200 | o += "0x%02x%s (%s)\n" % (d, wr, ack) | |
201 | bitcount = data = 0 | |
202 | ||
203 | # STOP condition (P): SDA = rising, SCL = high | |
204 | elif (oldsda == 0 and sda == 1) and scl == 1: | |
205 | o += "%d\t\tSTOP\n" % samplenum | |
206 | state = IDLE | |
207 | ||
208 | # Save current SDA/SCL values for the next round. | |
209 | oldscl = scl | |
210 | oldsda = sda | |
211 | ||
212 | return o | |
213 | ||
214 | def register(): | |
215 | return { | |
216 | 'id': 'i2c', | |
217 | 'name': 'I2C', | |
218 | 'desc': 'Inter-Integrated Circuit (I2C) bus', | |
219 | 'inputformats': ['raw'], | |
220 | 'signalnames': { | |
221 | 'SCL': 'Serial clock line', | |
222 | 'SDA': 'Serial data line', | |
223 | }, | |
224 | 'outputformats': ['i2c'], | |
225 | } | |
226 | ||
227 | # Use psyco (if available) as it results in huge performance improvements. | |
228 | try: | |
229 | import psyco | |
230 | psyco.bind(decode) | |
231 | except ImportError: | |
232 | pass | |
233 |