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0588ed70 | 1 | ## |
50bd5d25 | 2 | ## This file is part of the libsigrokdecode project. |
0588ed70 | 3 | ## |
d94ff143 | 4 | ## Copyright (C) 2010-2013 Uwe Hermann <uwe@hermann-uwe.de> |
0588ed70 UH |
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 | ||
0588ed70 | 21 | # I2C protocol decoder |
0588ed70 UH |
22 | |
23 | # TODO: Look into arbitration, collision detection, clock synchronisation, etc. | |
9e95e4d8 | 24 | # TODO: Implement support for 10bit slave addresses. |
0588ed70 UH |
25 | # TODO: Implement support for inverting SDA/SCL levels (0->1 and 1->0). |
26 | # TODO: Implement support for detecting various bus errors. | |
23fb2e12 | 27 | |
677d597b | 28 | import sigrokdecode as srd |
b2c19614 | 29 | |
f1428c4c UH |
30 | ''' |
31 | Protocol output format: | |
32 | ||
33 | I2C packet: | |
34 | [<cmd>, <data>] | |
35 | ||
36 | <cmd> is one of: | |
37 | - 'START' (START condition) | |
38 | - 'START REPEAT' (Repeated START condition) | |
39 | - 'ADDRESS READ' (Slave address, read) | |
40 | - 'ADDRESS WRITE' (Slave address, write) | |
41 | - 'DATA READ' (Data, read) | |
42 | - 'DATA WRITE' (Data, write) | |
43 | - 'STOP' (STOP condition) | |
44 | - 'ACK' (ACK bit) | |
45 | - 'NACK' (NACK bit) | |
46 | ||
47 | <data> is the data or address byte associated with the 'ADDRESS*' and 'DATA*' | |
48 | command. Slave addresses do not include bit 0 (the READ/WRITE indication bit). | |
49 | For example, a slave address field could be 0x51 (instead of 0xa2). | |
50 | For 'START', 'START REPEAT', 'STOP', 'ACK', and 'NACK' <data> is None. | |
51 | ''' | |
52 | ||
d94ff143 | 53 | # CMD: [annotation-type-index, long annotation, short annotation] |
1541976f | 54 | proto = { |
d94ff143 UH |
55 | 'START': [0, 'Start', 'S'], |
56 | 'START REPEAT': [1, 'Start repeat', 'Sr'], | |
57 | 'STOP': [2, 'Stop', 'P'], | |
58 | 'ACK': [3, 'ACK', 'A'], | |
59 | 'NACK': [4, 'NACK', 'N'], | |
60 | 'ADDRESS READ': [5, 'Address read', 'AR'], | |
61 | 'ADDRESS WRITE': [6, 'Address write', 'AW'], | |
62 | 'DATA READ': [7, 'Data read', 'DR'], | |
63 | 'DATA WRITE': [8, 'Data write', 'DW'], | |
15969949 | 64 | } |
e5080882 | 65 | |
677d597b | 66 | class Decoder(srd.Decoder): |
a2c2afd9 | 67 | api_version = 1 |
67e847fd | 68 | id = 'i2c' |
f39d2404 | 69 | name = 'I2C' |
9a12a6e7 | 70 | longname = 'Inter-Integrated Circuit' |
a465436e | 71 | desc = 'Two-wire, multi-master, serial bus.' |
f39d2404 UH |
72 | license = 'gplv2+' |
73 | inputs = ['logic'] | |
74 | outputs = ['i2c'] | |
bc5f5a43 BV |
75 | probes = [ |
76 | {'id': 'scl', 'name': 'SCL', 'desc': 'Serial clock line'}, | |
77 | {'id': 'sda', 'name': 'SDA', 'desc': 'Serial data line'}, | |
78 | ] | |
b77614bc | 79 | optional_probes = [] |
f39d2404 | 80 | options = { |
d94ff143 | 81 | 'address_format': ['Displayed slave address format', 'shifted'], |
ad2dc0de | 82 | } |
e97b6ef5 | 83 | annotations = [ |
d94ff143 UH |
84 | ['Start', 'Start condition'], |
85 | ['Repeat start', 'Repeat start condition'], | |
86 | ['Stop', 'Stop condition'], | |
87 | ['ACK', 'ACK'], | |
88 | ['NACK', 'NACK'], | |
89 | ['Address read', 'Address read'], | |
90 | ['Address write', 'Address write'], | |
91 | ['Data read', 'Data read'], | |
92 | ['Data write', 'Data write'], | |
93 | ['Warnings', 'Human-readable warnings'], | |
15969949 | 94 | ] |
0588ed70 | 95 | |
3643fc3f | 96 | def __init__(self, **kwargs): |
c4975078 BV |
97 | self.startsample = -1 |
98 | self.samplenum = None | |
f39d2404 UH |
99 | self.bitcount = 0 |
100 | self.databyte = 0 | |
101 | self.wr = -1 | |
5dd9af5b | 102 | self.is_repeat_start = 0 |
2b716038 | 103 | self.state = 'FIND START' |
95097f31 UH |
104 | self.oldscl = 1 |
105 | self.oldsda = 1 | |
d94ff143 | 106 | self.oldpins = [1, 1] |
f39d2404 | 107 | |
8915b346 | 108 | def start(self): |
56202222 UH |
109 | self.out_proto = self.add(srd.OUTPUT_PROTO, 'i2c') |
110 | self.out_ann = self.add(srd.OUTPUT_ANN, 'i2c') | |
3643fc3f | 111 | |
decde15e UH |
112 | def report(self): |
113 | pass | |
114 | ||
d94ff143 UH |
115 | def putx(self, data): |
116 | self.put(self.startsample, self.samplenum, self.out_ann, data) | |
117 | ||
118 | def putp(self, data): | |
119 | self.put(self.startsample, self.samplenum, self.out_proto, data) | |
120 | ||
7b86f0bc | 121 | def is_start_condition(self, scl, sda): |
eb7082c9 | 122 | # START condition (S): SDA = falling, SCL = high |
7b86f0bc UH |
123 | if (self.oldsda == 1 and sda == 0) and scl == 1: |
124 | return True | |
125 | return False | |
126 | ||
127 | def is_data_bit(self, scl, sda): | |
eb7082c9 | 128 | # Data sampling of receiver: SCL = rising |
7b86f0bc UH |
129 | if self.oldscl == 0 and scl == 1: |
130 | return True | |
131 | return False | |
132 | ||
133 | def is_stop_condition(self, scl, sda): | |
eb7082c9 | 134 | # STOP condition (P): SDA = rising, SCL = high |
7b86f0bc UH |
135 | if (self.oldsda == 0 and sda == 1) and scl == 1: |
136 | return True | |
137 | return False | |
138 | ||
e5080882 | 139 | def found_start(self, scl, sda): |
c4975078 | 140 | self.startsample = self.samplenum |
c4975078 | 141 | cmd = 'START REPEAT' if (self.is_repeat_start == 1) else 'START' |
d94ff143 UH |
142 | self.putp([cmd, None]) |
143 | self.putx([proto[cmd][0], proto[cmd][1:]]) | |
2b716038 | 144 | self.state = 'FIND ADDRESS' |
7b86f0bc | 145 | self.bitcount = self.databyte = 0 |
5dd9af5b | 146 | self.is_repeat_start = 1 |
7b86f0bc | 147 | self.wr = -1 |
7b86f0bc | 148 | |
c4975078 | 149 | # Gather 8 bits of data plus the ACK/NACK bit. |
e5080882 | 150 | def found_address_or_data(self, scl, sda): |
7b86f0bc UH |
151 | # Address and data are transmitted MSB-first. |
152 | self.databyte <<= 1 | |
153 | self.databyte |= sda | |
154 | ||
c4975078 BV |
155 | if self.bitcount == 0: |
156 | self.startsample = self.samplenum | |
157 | ||
7b86f0bc | 158 | # Return if we haven't collected all 8 + 1 bits, yet. |
c4975078 | 159 | self.bitcount += 1 |
1b75abfd | 160 | if self.bitcount != 8: |
eb7082c9 | 161 | return |
7b86f0bc | 162 | |
1b75abfd BV |
163 | # We triggered on the ACK/NACK bit, but won't report that until later. |
164 | self.startsample -= 1 | |
165 | ||
d94ff143 | 166 | d = self.databyte |
2b716038 | 167 | if self.state == 'FIND ADDRESS': |
7b86f0bc | 168 | # The READ/WRITE bit is only in address bytes, not data bytes. |
bf1c3f4d | 169 | self.wr = 0 if (self.databyte & 1) else 1 |
d94ff143 UH |
170 | if self.options['address_format'] == 'shifted': |
171 | d = d >> 1 | |
15969949 | 172 | |
2b716038 | 173 | if self.state == 'FIND ADDRESS' and self.wr == 1: |
a2d2aff2 | 174 | cmd = 'ADDRESS WRITE' |
2b716038 | 175 | elif self.state == 'FIND ADDRESS' and self.wr == 0: |
a2d2aff2 | 176 | cmd = 'ADDRESS READ' |
2b716038 | 177 | elif self.state == 'FIND DATA' and self.wr == 1: |
a2d2aff2 | 178 | cmd = 'DATA WRITE' |
2b716038 | 179 | elif self.state == 'FIND DATA' and self.wr == 0: |
a2d2aff2 | 180 | cmd = 'DATA READ' |
eb7082c9 | 181 | |
d94ff143 UH |
182 | self.putp([cmd, d]) |
183 | self.putx([proto[cmd][0], ['%s: %02X' % (proto[cmd][1], d), | |
184 | '%s: %02X' % (proto[cmd][2], d), '%02X' % d]]) | |
7b86f0bc | 185 | |
1b75abfd | 186 | # Done with this packet. |
7b86f0bc | 187 | self.startsample = -1 |
1b75abfd | 188 | self.bitcount = self.databyte = 0 |
2b716038 | 189 | self.state = 'FIND ACK' |
7b86f0bc | 190 | |
1b75abfd BV |
191 | def get_ack(self, scl, sda): |
192 | self.startsample = self.samplenum | |
d94ff143 UH |
193 | cmd = 'NACK' if (sda == 1) else 'ACK' |
194 | self.putp([cmd, None]) | |
195 | self.putx([proto[cmd][0], proto[cmd][1:]]) | |
1b75abfd BV |
196 | # There could be multiple data bytes in a row, so either find |
197 | # another data byte or a STOP condition next. | |
2b716038 | 198 | self.state = 'FIND DATA' |
7b86f0bc | 199 | |
e5080882 | 200 | def found_stop(self, scl, sda): |
c4975078 | 201 | self.startsample = self.samplenum |
d94ff143 UH |
202 | cmd = 'STOP' |
203 | self.putp([cmd, None]) | |
204 | self.putx([proto[cmd][0], proto[cmd][1:]]) | |
2b716038 | 205 | self.state = 'FIND START' |
5dd9af5b | 206 | self.is_repeat_start = 0 |
7b86f0bc UH |
207 | self.wr = -1 |
208 | ||
2b9837d9 | 209 | def decode(self, ss, es, data): |
2fcd7c22 UH |
210 | for (self.samplenum, pins) in data: |
211 | ||
212 | # Ignore identical samples early on (for performance reasons). | |
213 | if self.oldpins == pins: | |
214 | continue | |
215 | self.oldpins, (scl, sda) = pins, pins | |
f39d2404 | 216 | |
f39d2404 UH |
217 | # TODO: Wait until the bus is idle (SDA = SCL = 1) first? |
218 | ||
7b86f0bc | 219 | # State machine. |
2b716038 | 220 | if self.state == 'FIND START': |
7b86f0bc | 221 | if self.is_start_condition(scl, sda): |
e5080882 | 222 | self.found_start(scl, sda) |
2b716038 | 223 | elif self.state == 'FIND ADDRESS': |
7b86f0bc | 224 | if self.is_data_bit(scl, sda): |
e5080882 | 225 | self.found_address_or_data(scl, sda) |
2b716038 | 226 | elif self.state == 'FIND DATA': |
7b86f0bc | 227 | if self.is_data_bit(scl, sda): |
e5080882 | 228 | self.found_address_or_data(scl, sda) |
7b86f0bc | 229 | elif self.is_start_condition(scl, sda): |
e5080882 | 230 | self.found_start(scl, sda) |
7b86f0bc | 231 | elif self.is_stop_condition(scl, sda): |
e5080882 | 232 | self.found_stop(scl, sda) |
2b716038 | 233 | elif self.state == 'FIND ACK': |
1b75abfd BV |
234 | if self.is_data_bit(scl, sda): |
235 | self.get_ack(scl, sda) | |
7b86f0bc | 236 | else: |
0eeeb544 | 237 | raise Exception('Invalid state: %s' % self.state) |
f39d2404 UH |
238 | |
239 | # Save current SDA/SCL values for the next round. | |
240 | self.oldscl = scl | |
241 | self.oldsda = sda | |
242 |