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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 | # I2C protocol decoder | |
22 | ||
23 | # TODO: Look into arbitration, collision detection, clock synchronisation, etc. | |
24 | # TODO: Handle clock stretching. | |
25 | # TODO: Handle combined messages / repeated START. | |
26 | # TODO: Implement support for 7bit and 10bit slave addresses. | |
27 | # TODO: Implement support for inverting SDA/SCL levels (0->1 and 1->0). | |
28 | # TODO: Implement support for detecting various bus errors. | |
29 | # TODO: I2C address of slaves. | |
30 | # TODO: Handle multiple different I2C devices on same bus | |
31 | # -> we need to decode multiple protocols at the same time. | |
32 | ||
33 | import sigrokdecode as srd | |
34 | ||
35 | # Annotation feed formats | |
36 | ANN_SHIFTED = 0 | |
37 | ANN_SHIFTED_SHORT = 1 | |
38 | ANN_RAW = 2 | |
39 | ||
40 | # Values are verbose and short annotation, respectively. | |
41 | proto = { | |
42 | 'START': ['START', 'S'], | |
43 | 'START REPEAT': ['START REPEAT', 'Sr'], | |
44 | 'STOP': ['STOP', 'P'], | |
45 | 'ACK': ['ACK', 'A'], | |
46 | 'NACK': ['NACK', 'N'], | |
47 | 'ADDRESS READ': ['ADDRESS READ', 'AR'], | |
48 | 'ADDRESS WRITE': ['ADDRESS WRITE', 'AW'], | |
49 | 'DATA READ': ['DATA READ', 'DR'], | |
50 | 'DATA WRITE': ['DATA WRITE', 'DW'], | |
51 | } | |
52 | ||
53 | class Decoder(srd.Decoder): | |
54 | api_version = 1 | |
55 | id = 'i2c' | |
56 | name = 'I2C' | |
57 | longname = 'Inter-Integrated Circuit' | |
58 | desc = 'I2C is a two-wire, multi-master, serial bus.' | |
59 | license = 'gplv2+' | |
60 | inputs = ['logic'] | |
61 | outputs = ['i2c'] | |
62 | probes = [ | |
63 | {'id': 'scl', 'name': 'SCL', 'desc': 'Serial clock line'}, | |
64 | {'id': 'sda', 'name': 'SDA', 'desc': 'Serial data line'}, | |
65 | ] | |
66 | optional_probes = [] | |
67 | options = { | |
68 | 'addressing': ['Slave addressing (in bits)', 7], # 7 or 10 | |
69 | } | |
70 | annotations = [ | |
71 | # ANN_SHIFTED | |
72 | ['7-bit shifted hex', | |
73 | 'Read/write bit shifted out from the 8-bit I2C slave address'], | |
74 | # ANN_SHIFTED_SHORT | |
75 | ['7-bit shifted hex (short)', | |
76 | 'Read/write bit shifted out from the 8-bit I2C slave address'], | |
77 | # ANN_RAW | |
78 | ['Raw hex', 'Unaltered raw data'], | |
79 | ] | |
80 | ||
81 | def __init__(self, **kwargs): | |
82 | self.startsample = -1 | |
83 | self.samplenum = None | |
84 | self.bitcount = 0 | |
85 | self.databyte = 0 | |
86 | self.wr = -1 | |
87 | self.is_repeat_start = 0 | |
88 | self.state = 'FIND START' | |
89 | self.oldscl = None | |
90 | self.oldsda = None | |
91 | ||
92 | def start(self, metadata): | |
93 | self.out_proto = self.add(srd.OUTPUT_PROTO, 'i2c') | |
94 | self.out_ann = self.add(srd.OUTPUT_ANN, 'i2c') | |
95 | ||
96 | def report(self): | |
97 | pass | |
98 | ||
99 | def is_start_condition(self, scl, sda): | |
100 | # START condition (S): SDA = falling, SCL = high | |
101 | if (self.oldsda == 1 and sda == 0) and scl == 1: | |
102 | return True | |
103 | return False | |
104 | ||
105 | def is_data_bit(self, scl, sda): | |
106 | # Data sampling of receiver: SCL = rising | |
107 | if self.oldscl == 0 and scl == 1: | |
108 | return True | |
109 | return False | |
110 | ||
111 | def is_stop_condition(self, scl, sda): | |
112 | # STOP condition (P): SDA = rising, SCL = high | |
113 | if (self.oldsda == 0 and sda == 1) and scl == 1: | |
114 | return True | |
115 | return False | |
116 | ||
117 | def found_start(self, scl, sda): | |
118 | self.startsample = self.samplenum | |
119 | ||
120 | cmd = 'START REPEAT' if (self.is_repeat_start == 1) else 'START' | |
121 | self.put(self.out_proto, [cmd, None]) | |
122 | self.put(self.out_ann, [ANN_SHIFTED, [proto[cmd][0]]]) | |
123 | self.put(self.out_ann, [ANN_SHIFTED_SHORT, [proto[cmd][1]]]) | |
124 | ||
125 | self.state = 'FIND ADDRESS' | |
126 | self.bitcount = self.databyte = 0 | |
127 | self.is_repeat_start = 1 | |
128 | self.wr = -1 | |
129 | ||
130 | # Gather 8 bits of data plus the ACK/NACK bit. | |
131 | def found_address_or_data(self, scl, sda): | |
132 | # Address and data are transmitted MSB-first. | |
133 | self.databyte <<= 1 | |
134 | self.databyte |= sda | |
135 | ||
136 | if self.bitcount == 0: | |
137 | self.startsample = self.samplenum | |
138 | ||
139 | # Return if we haven't collected all 8 + 1 bits, yet. | |
140 | self.bitcount += 1 | |
141 | if self.bitcount != 8: | |
142 | return | |
143 | ||
144 | # We triggered on the ACK/NACK bit, but won't report that until later. | |
145 | self.startsample -= 1 | |
146 | ||
147 | # Send raw output annotation before we start shifting out | |
148 | # read/write and ACK/NACK bits. | |
149 | self.put(self.out_ann, [ANN_RAW, ['0x%.2x' % self.databyte]]) | |
150 | ||
151 | if self.state == 'FIND ADDRESS': | |
152 | # The READ/WRITE bit is only in address bytes, not data bytes. | |
153 | self.wr = 0 if (self.databyte & 1) else 1 | |
154 | d = self.databyte >> 1 | |
155 | elif self.state == 'FIND DATA': | |
156 | d = self.databyte | |
157 | ||
158 | if self.state == 'FIND ADDRESS' and self.wr == 1: | |
159 | cmd = 'ADDRESS WRITE' | |
160 | elif self.state == 'FIND ADDRESS' and self.wr == 0: | |
161 | cmd = 'ADDRESS READ' | |
162 | elif self.state == 'FIND DATA' and self.wr == 1: | |
163 | cmd = 'DATA WRITE' | |
164 | elif self.state == 'FIND DATA' and self.wr == 0: | |
165 | cmd = 'DATA READ' | |
166 | ||
167 | self.put(self.out_proto, [cmd, d]) | |
168 | self.put(self.out_ann, [ANN_SHIFTED, [proto[cmd][0], '0x%02x' % d]]) | |
169 | self.put(self.out_ann, [ANN_SHIFTED_SHORT, [proto[cmd][1], '0x%02x' % d]]) | |
170 | ||
171 | # Done with this packet. | |
172 | self.startsample = -1 | |
173 | self.bitcount = self.databyte = 0 | |
174 | self.state = 'FIND ACK' | |
175 | ||
176 | def get_ack(self, scl, sda): | |
177 | self.startsample = self.samplenum | |
178 | ack_bit = 'NACK' if (sda == 1) else 'ACK' | |
179 | self.put(self.out_proto, [ack_bit, None]) | |
180 | self.put(self.out_ann, [ANN_SHIFTED, [proto[ack_bit][0]]]) | |
181 | self.put(self.out_ann, [ANN_SHIFTED_SHORT, [proto[ack_bit][1]]]) | |
182 | # There could be multiple data bytes in a row, so either find | |
183 | # another data byte or a STOP condition next. | |
184 | self.state = 'FIND DATA' | |
185 | ||
186 | def found_stop(self, scl, sda): | |
187 | self.startsample = self.samplenum | |
188 | self.put(self.out_proto, ['STOP', None]) | |
189 | self.put(self.out_ann, [ANN_SHIFTED, [proto['STOP'][0]]]) | |
190 | self.put(self.out_ann, [ANN_SHIFTED_SHORT, [proto['STOP'][1]]]) | |
191 | ||
192 | self.state = 'FIND START' | |
193 | self.is_repeat_start = 0 | |
194 | self.wr = -1 | |
195 | ||
196 | def put(self, output_id, data): | |
197 | # Inject sample range into the call up to sigrok. | |
198 | super(Decoder, self).put(self.startsample, self.samplenum, output_id, data) | |
199 | ||
200 | def decode(self, ss, es, data): | |
201 | for (self.samplenum, (scl, sda)) in data: | |
202 | ||
203 | # First sample: Save SCL/SDA value. | |
204 | if self.oldscl == None: | |
205 | self.oldscl = scl | |
206 | self.oldsda = sda | |
207 | continue | |
208 | ||
209 | # TODO: Wait until the bus is idle (SDA = SCL = 1) first? | |
210 | ||
211 | # State machine. | |
212 | if self.state == 'FIND START': | |
213 | if self.is_start_condition(scl, sda): | |
214 | self.found_start(scl, sda) | |
215 | elif self.state == 'FIND ADDRESS': | |
216 | if self.is_data_bit(scl, sda): | |
217 | self.found_address_or_data(scl, sda) | |
218 | elif self.state == 'FIND DATA': | |
219 | if self.is_data_bit(scl, sda): | |
220 | self.found_address_or_data(scl, sda) | |
221 | elif self.is_start_condition(scl, sda): | |
222 | self.found_start(scl, sda) | |
223 | elif self.is_stop_condition(scl, sda): | |
224 | self.found_stop(scl, sda) | |
225 | elif self.state == 'FIND ACK': | |
226 | if self.is_data_bit(scl, sda): | |
227 | self.get_ack(scl, sda) | |
228 | else: | |
229 | raise Exception('Invalid state %d' % self.STATE) | |
230 | ||
231 | # Save current SDA/SCL values for the next round. | |
232 | self.oldscl = scl | |
233 | self.oldsda = sda | |
234 |