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1 | ## | |
2 | ## This file is part of the sigrok project. | |
3 | ## | |
4 | ## Copyright (C) 2010-2011 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 | # Data bit sampling: SCL = rising | |
43 | # STOP condition (P): SDA = rising, SCL = high | |
44 | # | |
45 | # All data bytes on SDA are exactly 8 bits long (transmitted MSB-first). | |
46 | # Each byte has to be followed by a 9th ACK/NACK bit. If that bit is low, | |
47 | # that indicates an ACK, if it's high that indicates a NACK. | |
48 | # | |
49 | # After the first START condition, a master sends the device address of the | |
50 | # slave it wants to talk to. Slave addresses are 7 bits long (MSB-first). | |
51 | # After those 7 bits, a data direction bit is sent. If the bit is low that | |
52 | # indicates a WRITE operation, if it's high that indicates a READ operation. | |
53 | # | |
54 | # Later an optional 10bit slave addressing scheme was added. | |
55 | # | |
56 | # Documentation: | |
57 | # http://www.nxp.com/acrobat/literature/9398/39340011.pdf (v2.1 spec) | |
58 | # http://www.nxp.com/acrobat/usermanuals/UM10204_3.pdf (v3 spec) | |
59 | # http://en.wikipedia.org/wiki/I2C | |
60 | # | |
61 | ||
62 | # TODO: Look into arbitration, collision detection, clock synchronisation, etc. | |
63 | # TODO: Handle clock stretching. | |
64 | # TODO: Handle combined messages / repeated START. | |
65 | # TODO: Implement support for 7bit and 10bit slave addresses. | |
66 | # TODO: Implement support for inverting SDA/SCL levels (0->1 and 1->0). | |
67 | # TODO: Implement support for detecting various bus errors. | |
68 | ||
69 | # | |
70 | # I2C output format: | |
71 | # | |
72 | # The output consists of a (Python) list of I2C "packets", each of which | |
73 | # has an (implicit) index number (its index in the list). | |
74 | # Each packet consists of a Python dict with certain key/value pairs. | |
75 | # | |
76 | # TODO: Make this a list later instead of a dict? | |
77 | # | |
78 | # 'type': (string) | |
79 | # - 'S' (START condition) | |
80 | # - 'Sr' (Repeated START) | |
81 | # - 'AR' (Address, read) | |
82 | # - 'AW' (Address, write) | |
83 | # - 'DR' (Data, read) | |
84 | # - 'DW' (Data, write) | |
85 | # - 'P' (STOP condition) | |
86 | # 'range': (tuple of 2 integers, the min/max samplenumber of this range) | |
87 | # - (min, max) | |
88 | # - min/max can also be identical. | |
89 | # 'data': (actual data as integer ???) TODO: This can be very variable... | |
90 | # 'ann': (string; additional annotations / comments) | |
91 | # | |
92 | # Example output: | |
93 | # [{'type': 'S', 'range': (150, 160), 'data': None, 'ann': 'Foobar'}, | |
94 | # {'type': 'AW', 'range': (200, 300), 'data': 0x50, 'ann': 'Slave 4'}, | |
95 | # {'type': 'DW', 'range': (310, 370), 'data': 0x00, 'ann': 'Init cmd'}, | |
96 | # {'type': 'AR', 'range': (500, 560), 'data': 0x50, 'ann': 'Get stat'}, | |
97 | # {'type': 'DR', 'range': (580, 640), 'data': 0xfe, 'ann': 'OK'}, | |
98 | # {'type': 'P', 'range': (650, 660), 'data': None, 'ann': None}] | |
99 | # | |
100 | # Possible other events: | |
101 | # - Error event in case protocol looks broken: | |
102 | # [{'type': 'ERROR', 'range': (min, max), | |
103 | # 'data': TODO, 'ann': 'This is not a Microchip 24XX64 EEPROM'}, | |
104 | # [{'type': 'ERROR', 'range': (min, max), | |
105 | # 'data': TODO, 'ann': 'TODO'}, | |
106 | # - TODO: Make list of possible errors accessible as metadata? | |
107 | # | |
108 | # TODO: I2C address of slaves. | |
109 | # TODO: Handle multiple different I2C devices on same bus | |
110 | # -> we need to decode multiple protocols at the same time. | |
111 | # TODO: range: Always contiguous? Splitted ranges? Multiple per event? | |
112 | # | |
113 | ||
114 | # | |
115 | # I2C input format: | |
116 | # | |
117 | # signals: | |
118 | # [[id, channel, description], ...] # TODO | |
119 | # | |
120 | # Example: | |
121 | # {'id': 'SCL', 'ch': 5, 'desc': 'Serial clock line'} | |
122 | # {'id': 'SDA', 'ch': 7, 'desc': 'Serial data line'} | |
123 | # ... | |
124 | # | |
125 | # {'inbuf': [...], | |
126 | # 'signals': [{'SCL': }]} | |
127 | # | |
128 | ||
129 | # States | |
130 | FIND_START = 0 | |
131 | FIND_ADDRESS = 1 | |
132 | FIND_DATA = 2 | |
133 | ||
134 | class Sample(): | |
135 | def __init__(self, data): | |
136 | self.data = data | |
137 | def probe(self, probe): | |
138 | s = ord(self.data[probe / 8]) & (1 << (probe % 8)) | |
139 | return True if s else False | |
140 | ||
141 | def sampleiter(data, unitsize): | |
142 | for i in range(0, len(data), unitsize): | |
143 | yield(Sample(data[i:i+unitsize])) | |
144 | ||
145 | class Decoder(): | |
146 | id = 'i2c' | |
147 | name = 'I2C' | |
148 | longname = 'Inter-Integrated Circuit (I2C) bus' | |
149 | desc = 'I2C is a two-wire, multi-master, serial bus.' | |
150 | longdesc = '...' | |
151 | author = 'Uwe Hermann' | |
152 | email = 'uwe@hermann-uwe.de' | |
153 | license = 'gplv2+' | |
154 | inputs = ['logic'] | |
155 | outputs = ['i2c'] | |
156 | probes = { | |
157 | 'scl': {'ch': 0, 'name': 'SCL', 'desc': 'Serial clock line'}, | |
158 | 'sda': {'ch': 1, 'name': 'SDA', 'desc': 'Serial data line'}, | |
159 | } | |
160 | options = { | |
161 | 'address-space': ['Address space (in bits)', 7], | |
162 | } | |
163 | ||
164 | def __init__(self, **kwargs): | |
165 | self.probes = Decoder.probes.copy() | |
166 | ||
167 | # TODO: Don't hardcode the number of channels. | |
168 | self.channels = 8 | |
169 | ||
170 | self.samplenum = 0 | |
171 | self.bitcount = 0 | |
172 | self.databyte = 0 | |
173 | self.wr = -1 | |
174 | self.startsample = -1 | |
175 | self.is_repeat_start = 0 | |
176 | ||
177 | self.state = FIND_START | |
178 | ||
179 | # Get the channel/probe number of the SCL/SDA signals. | |
180 | self.scl_bit = self.probes['scl']['ch'] | |
181 | self.sda_bit = self.probes['sda']['ch'] | |
182 | ||
183 | self.oldscl = None | |
184 | self.oldsda = None | |
185 | ||
186 | def start(self, metadata): | |
187 | self.unitsize = metadata["unitsize"] | |
188 | ||
189 | def report(self): | |
190 | pass | |
191 | ||
192 | def is_start_condition(self, scl, sda): | |
193 | """START condition (S): SDA = falling, SCL = high""" | |
194 | if (self.oldsda == 1 and sda == 0) and scl == 1: | |
195 | return True | |
196 | return False | |
197 | ||
198 | def is_data_bit(self, scl, sda): | |
199 | """Data sampling of receiver: SCL = rising""" | |
200 | if self.oldscl == 0 and scl == 1: | |
201 | return True | |
202 | return False | |
203 | ||
204 | def is_stop_condition(self, scl, sda): | |
205 | """STOP condition (P): SDA = rising, SCL = high""" | |
206 | if (self.oldsda == 0 and sda == 1) and scl == 1: | |
207 | return True | |
208 | return False | |
209 | ||
210 | def find_start(self, scl, sda): | |
211 | out = [] | |
212 | # o = {'type': 'S', 'range': (self.samplenum, self.samplenum), | |
213 | # 'data': None, 'ann': None}, | |
214 | o = (self.is_repeat_start == 1) and 'Sr' or 'S' | |
215 | out.append(o) | |
216 | self.state = FIND_ADDRESS | |
217 | self.bitcount = self.databyte = 0 | |
218 | self.is_repeat_start = 1 | |
219 | self.wr = -1 | |
220 | return out | |
221 | ||
222 | def find_address_or_data(self, scl, sda): | |
223 | """Gather 8 bits of data plus the ACK/NACK bit.""" | |
224 | out = o = [] | |
225 | ||
226 | if self.startsample == -1: | |
227 | self.startsample = self.samplenum | |
228 | self.bitcount += 1 | |
229 | ||
230 | # Address and data are transmitted MSB-first. | |
231 | self.databyte <<= 1 | |
232 | self.databyte |= sda | |
233 | ||
234 | # Return if we haven't collected all 8 + 1 bits, yet. | |
235 | if self.bitcount != 9: | |
236 | return [] | |
237 | ||
238 | # We received 8 address/data bits and the ACK/NACK bit. | |
239 | self.databyte >>= 1 # Shift out unwanted ACK/NACK bit here. | |
240 | ||
241 | ack = (sda == 1) and 'N' or 'A' | |
242 | ||
243 | if self.state == FIND_ADDRESS: | |
244 | d = self.databyte & 0xfe | |
245 | # The READ/WRITE bit is only in address bytes, not data bytes. | |
246 | self.wr = (self.databyte & 1) and 1 or 0 | |
247 | elif self.state == FIND_DATA: | |
248 | d = self.databyte | |
249 | else: | |
250 | # TODO: Error? | |
251 | pass | |
252 | ||
253 | # o = {'type': self.state, | |
254 | # 'range': (self.startsample, self.samplenum - 1), | |
255 | # 'data': d, 'ann': None} | |
256 | ||
257 | o = {'data': '0x%02x' % d} | |
258 | ||
259 | # TODO: Simplify. | |
260 | if self.state == FIND_ADDRESS and self.wr == 1: | |
261 | o['type'] = 'AW' | |
262 | elif self.state == FIND_ADDRESS and self.wr == 0: | |
263 | o['type'] = 'AR' | |
264 | elif self.state == FIND_DATA and self.wr == 1: | |
265 | o['type'] = 'DW' | |
266 | elif self.state == FIND_DATA and self.wr == 0: | |
267 | o['type'] = 'DR' | |
268 | ||
269 | out.append(o) | |
270 | ||
271 | # o = {'type': ack, 'range': (self.samplenum, self.samplenum), | |
272 | # 'data': None, 'ann': None} | |
273 | o = ack | |
274 | out.append(o) | |
275 | self.bitcount = self.databyte = 0 | |
276 | self.startsample = -1 | |
277 | ||
278 | if self.state == FIND_ADDRESS: | |
279 | self.state = FIND_DATA | |
280 | elif self.state == FIND_DATA: | |
281 | # There could be multiple data bytes in a row. | |
282 | # So, either find a STOP condition or another data byte next. | |
283 | pass | |
284 | ||
285 | return out | |
286 | ||
287 | def find_stop(self, scl, sda): | |
288 | out = o = [] | |
289 | ||
290 | # o = {'type': 'P', 'range': (self.samplenum, self.samplenum), | |
291 | # 'data': None, 'ann': None}, | |
292 | o = 'P' | |
293 | out.append(o) | |
294 | self.state = FIND_START | |
295 | self.is_repeat_start = 0 | |
296 | self.wr = -1 | |
297 | ||
298 | return out | |
299 | ||
300 | def decode(self, data): | |
301 | """I2C protocol decoder""" | |
302 | ||
303 | out = [] | |
304 | o = ack = d = '' | |
305 | ||
306 | # We should accept a list of samples and iterate... | |
307 | for sample in sampleiter(data['data'], self.unitsize): | |
308 | ||
309 | # TODO: Eliminate the need for ord(). | |
310 | s = ord(sample.data) | |
311 | ||
312 | # TODO: Start counting at 0 or 1? | |
313 | self.samplenum += 1 | |
314 | ||
315 | # First sample: Save SCL/SDA value. | |
316 | if self.oldscl == None: | |
317 | # Get SCL/SDA bit values (0/1 for low/high) of the first sample. | |
318 | self.oldscl = (s & (1 << self.scl_bit)) >> self.scl_bit | |
319 | self.oldsda = (s & (1 << self.sda_bit)) >> self.sda_bit | |
320 | continue | |
321 | ||
322 | # Get SCL/SDA bit values (0/1 for low/high). | |
323 | scl = (s & (1 << self.scl_bit)) >> self.scl_bit | |
324 | sda = (s & (1 << self.sda_bit)) >> self.sda_bit | |
325 | ||
326 | # TODO: Wait until the bus is idle (SDA = SCL = 1) first? | |
327 | ||
328 | # State machine. | |
329 | if self.state == FIND_START: | |
330 | if self.is_start_condition(scl, sda): | |
331 | out += self.find_start(scl, sda) | |
332 | elif self.state == FIND_ADDRESS: | |
333 | if self.is_data_bit(scl, sda): | |
334 | out += self.find_address_or_data(scl, sda) | |
335 | elif self.state == FIND_DATA: | |
336 | if self.is_data_bit(scl, sda): | |
337 | out += self.find_address_or_data(scl, sda) | |
338 | elif self.is_start_condition(scl, sda): | |
339 | out += self.find_start(scl, sda) | |
340 | elif self.is_stop_condition(scl, sda): | |
341 | out += self.find_stop(scl, sda) | |
342 | else: | |
343 | # TODO: Error? | |
344 | pass | |
345 | ||
346 | # Save current SDA/SCL values for the next round. | |
347 | self.oldscl = scl | |
348 | self.oldsda = sda | |
349 | ||
350 | if out != []: | |
351 | sigrok.put(out) | |
352 | ||
353 | import sigrok | |
354 | ||
355 | sigrok.register(Decoder) | |
356 |