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1 | ## | |
2 | ## This file is part of the sigrok project. | |
3 | ## | |
4 | ## Copyright (C) 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 | # UART protocol decoder | |
23 | # | |
24 | ||
25 | # | |
26 | # Universal Asynchronous Receiver Transmitter (UART) is a simple serial | |
27 | # communication protocol which allows two devices to talk to each other. | |
28 | # | |
29 | # It uses just two data signals and a ground (GND) signal: | |
30 | # - RX/RXD: Receive signal | |
31 | # - TX/TXD: Transmit signal | |
32 | # | |
33 | # The protocol is asynchronous, i.e., there is no dedicated clock signal. | |
34 | # Rather, both devices have to agree on a baudrate (number of bits to be | |
35 | # transmitted per second) beforehand. Baudrates can be arbitrary in theory, | |
36 | # but usually the choice is limited by the hardware UARTs that are used. | |
37 | # Common values are 9600 or 115200. | |
38 | # | |
39 | # The protocol allows full-duplex transmission, i.e. both devices can send | |
40 | # data at the same time. However, unlike SPI (which is always full-duplex, | |
41 | # i.e., each send operation is automatically also a receive operation), UART | |
42 | # allows one-way communication, too. In such a case only one signal (and GND) | |
43 | # is required. | |
44 | # | |
45 | # The data is sent over the TX line in so-called 'frames', which consist of: | |
46 | # - Exactly one start bit (always 0/low). | |
47 | # - Between 5 and 9 data bits. | |
48 | # - An (optional) parity bit. | |
49 | # - One or more stop bit(s). | |
50 | # | |
51 | # The idle state of the RX/TX line is 1/high. As the start bit is 0/low, the | |
52 | # receiver can continually monitor its RX line for a falling edge, in order | |
53 | # to detect the start bit. | |
54 | # | |
55 | # Once detected, it can (due to the agreed-upon baudrate and thus the known | |
56 | # width/duration of one UART bit) sample the state of the RX line "in the | |
57 | # middle" of each (start/data/parity/stop) bit it wants to analyze. | |
58 | # | |
59 | # It is configurable whether there is a parity bit in a frame, and if yes, | |
60 | # which type of parity is used: | |
61 | # - None: No parity bit is included. | |
62 | # - Odd: The number of 1 bits in the data (and parity bit itself) is odd. | |
63 | # - Even: The number of 1 bits in the data (and parity bit itself) is even. | |
64 | # - Mark/one: The parity bit is always 1/high (also called 'mark state'). | |
65 | # - Space/zero: The parity bit is always 0/low (also called 'space state'). | |
66 | # | |
67 | # It is also configurable how many stop bits are to be used: | |
68 | # - 1 stop bit (most common case) | |
69 | # - 2 stop bits | |
70 | # - 1.5 stop bits (i.e., one stop bit, but 1.5 times the UART bit width) | |
71 | # - 0.5 stop bits (i.e., one stop bit, but 0.5 times the UART bit width) | |
72 | # | |
73 | # The bit order of the 5-9 data bits is LSB-first. | |
74 | # | |
75 | # Possible special cases: | |
76 | # - One or both data lines could be inverted, which also means that the idle | |
77 | # state of the signal line(s) is low instead of high. | |
78 | # - Only the data bits on one or both data lines (and the parity bit) could | |
79 | # be inverted (but the start/stop bits remain non-inverted). | |
80 | # - The bit order could be MSB-first instead of LSB-first. | |
81 | # - The baudrate could change in the middle of the communication. This only | |
82 | # happens in very special cases, and can only work if both devices know | |
83 | # to which baudrate they are to switch, and when. | |
84 | # - Theoretically, the baudrate on RX and the one on TX could also be | |
85 | # different, but that's a very obscure case and probably doesn't happen | |
86 | # very often in practice. | |
87 | # | |
88 | # Error conditions: | |
89 | # - If there is a parity bit, but it doesn't match the expected parity, | |
90 | # this is called a 'parity error'. | |
91 | # - If there are no stop bit(s), that's called a 'frame error'. | |
92 | # | |
93 | # More information: | |
94 | # TODO: URLs | |
95 | # | |
96 | ||
97 | # | |
98 | # Protocol output format: | |
99 | # put(<startsample>, <endsample>, self.out_proto, <packet>) | |
100 | # | |
101 | # The <packet> is a list with two entries: | |
102 | # [<packet-type>, <packet-data>] | |
103 | # | |
104 | # Valid packet-type values: T_START, T_DATA, T_PARITY, T_STOP, T_INVALID_START, | |
105 | # T_INVALID_STOP, T_PARITY_ERROR | |
106 | # | |
107 | # The packet-data field has the following format and meaning: | |
108 | # - T_START: The data is the (integer) value of the start bit (0 or 1). | |
109 | # - T_DATA: The data is the (integer) value of the UART data. Valid values | |
110 | # range from 0 to 512 (as the data can be up to 9 bits in size). | |
111 | # - T_PARITY: The data is the (integer) value of the parity bit (0 or 1). | |
112 | # - T_STOP: The data is the (integer) value of the stop bit (0 or 1). | |
113 | # - T_INVALID_START: The data is the (integer) value of the start bit (0 or 1). | |
114 | # - T_INVALID_STOP: The data is the (integer) value of the stop bit (0 or 1). | |
115 | # - T_PARITY_ERROR: The data is a tuple with two entries. The first one is | |
116 | # the expected parity value, the second is the actual parity value. | |
117 | # | |
118 | # Examples: | |
119 | # [T_START, 0] | |
120 | # [T_DATA, 65] | |
121 | # [T_PARITY, 0] | |
122 | # [T_STOP, 1] | |
123 | # [T_INVALID_START, 1] | |
124 | # [T_INVALID_STOP, 0] | |
125 | # [T_PARITY_ERROR, (0, 1)] | |
126 | # | |
127 | ||
128 | import sigrokdecode as srd | |
129 | ||
130 | # States | |
131 | WAIT_FOR_START_BIT = 0 | |
132 | GET_START_BIT = 1 | |
133 | GET_DATA_BITS = 2 | |
134 | GET_PARITY_BIT = 3 | |
135 | GET_STOP_BITS = 4 | |
136 | ||
137 | # Parity options | |
138 | PARITY_NONE = 0 | |
139 | PARITY_ODD = 1 | |
140 | PARITY_EVEN = 2 | |
141 | PARITY_ZERO = 3 | |
142 | PARITY_ONE = 4 | |
143 | ||
144 | # Stop bit options | |
145 | STOP_BITS_0_5 = 0 | |
146 | STOP_BITS_1 = 1 | |
147 | STOP_BITS_1_5 = 2 | |
148 | STOP_BITS_2 = 3 | |
149 | ||
150 | # Bit order options | |
151 | LSB_FIRST = 0 | |
152 | MSB_FIRST = 1 | |
153 | ||
154 | # Annotation feed formats | |
155 | ANN_ASCII = 0 | |
156 | ANN_DEC = 1 | |
157 | ANN_HEX = 2 | |
158 | ANN_OCT = 3 | |
159 | ANN_BITS = 4 | |
160 | ||
161 | # Protocol output packet types | |
162 | T_START = 0 | |
163 | T_DATA = 1 | |
164 | T_PARITY = 2 | |
165 | T_STOP = 3 | |
166 | T_INVALID_START = 4 | |
167 | T_INVALID_STOP = 5 | |
168 | T_PARITY_ERROR = 6 | |
169 | ||
170 | # Given a parity type to check (odd, even, zero, one), the value of the | |
171 | # parity bit, the value of the data, and the length of the data (5-9 bits, | |
172 | # usually 8 bits) return True if the parity is correct, False otherwise. | |
173 | # PARITY_NONE is _not_ allowed as value for 'parity_type'. | |
174 | def parity_ok(parity_type, parity_bit, data, num_data_bits): | |
175 | ||
176 | # Handle easy cases first (parity bit is always 1 or 0). | |
177 | if parity_type == PARITY_ZERO: | |
178 | return parity_bit == 0 | |
179 | elif parity_type == PARITY_ONE: | |
180 | return parity_bit == 1 | |
181 | ||
182 | # Count number of 1 (high) bits in the data (and the parity bit itself!). | |
183 | parity = bin(data).count('1') + parity_bit | |
184 | ||
185 | # Check for odd/even parity. | |
186 | if parity_type == PARITY_ODD: | |
187 | return (parity % 2) == 1 | |
188 | elif parity_type == PARITY_EVEN: | |
189 | return (parity % 2) == 0 | |
190 | else: | |
191 | raise Exception('Invalid parity type: %d' % parity_type) | |
192 | ||
193 | class Decoder(srd.Decoder): | |
194 | id = 'uart' | |
195 | name = 'UART' | |
196 | longname = 'Universal Asynchronous Receiver/Transmitter (UART)' | |
197 | desc = 'Universal Asynchronous Receiver/Transmitter (UART)' | |
198 | longdesc = 'TODO.' | |
199 | author = 'Uwe Hermann' | |
200 | email = 'uwe@hermann-uwe.de' | |
201 | license = 'gplv2+' | |
202 | inputs = ['logic'] | |
203 | outputs = ['uart'] | |
204 | probes = [ | |
205 | # Allow specifying only one of the signals, e.g. if only one data | |
206 | # direction exists (or is relevant). | |
207 | {'id': 'rx', 'name': 'RX', 'desc': 'UART receive line'}, | |
208 | {'id': 'tx', 'name': 'TX', 'desc': 'UART transmit line'}, | |
209 | ] | |
210 | options = { | |
211 | 'baudrate': ['UART baud rate', 115200], | |
212 | 'num_data_bits': ['Data bits', 8], # Valid: 5-9. | |
213 | 'parity': ['Parity', PARITY_NONE], | |
214 | 'parity_check': ['Check parity', True], | |
215 | 'num_stop_bits': ['Stop bit(s)', STOP_BITS_1], | |
216 | 'bit_order': ['Bit order', LSB_FIRST], | |
217 | # TODO: Options to invert the signal(s). | |
218 | # ... | |
219 | } | |
220 | annotations = [ | |
221 | # ANN_ASCII | |
222 | ['ASCII', 'TODO: description'], | |
223 | # ANN_DEC | |
224 | ['Decimal', 'TODO: description'], | |
225 | # ANN_HEX | |
226 | ['Hex', 'TODO: description'], | |
227 | # ANN_OCT | |
228 | ['Octal', 'TODO: description'], | |
229 | # ANN_BITS | |
230 | ['Bits', 'TODO: description'], | |
231 | ] | |
232 | ||
233 | def __init__(self, **kwargs): | |
234 | # Set defaults, can be overridden in 'start'. | |
235 | self.baudrate = 115200 | |
236 | self.num_data_bits = 8 | |
237 | self.parity = PARITY_NONE | |
238 | self.check_parity = True | |
239 | self.num_stop_bits = 1 | |
240 | self.bit_order = LSB_FIRST | |
241 | ||
242 | self.samplenum = 0 | |
243 | self.frame_start = -1 | |
244 | self.startbit = -1 | |
245 | self.cur_data_bit = 0 | |
246 | self.databyte = 0 | |
247 | self.stopbit1 = -1 | |
248 | self.startsample = -1 | |
249 | ||
250 | # Initial state. | |
251 | self.staterx = WAIT_FOR_START_BIT | |
252 | ||
253 | self.oldrx = None | |
254 | self.oldtx = None | |
255 | ||
256 | def start(self, metadata): | |
257 | self.samplerate = metadata['samplerate'] | |
258 | self.out_proto = self.add(srd.OUTPUT_PROTO, 'uart') | |
259 | self.out_ann = self.add(srd.OUTPUT_ANN, 'uart') | |
260 | ||
261 | # TODO | |
262 | ### self.baudrate = metadata['baudrate'] | |
263 | ### self.num_data_bits = metadata['num_data_bits'] | |
264 | ### self.parity = metadata['parity'] | |
265 | ### self.parity_check = metadata['parity_check'] | |
266 | ### self.num_stop_bits = metadata['num_stop_bits'] | |
267 | ### self.bit_order = metadata['bit_order'] | |
268 | ||
269 | # The width of one UART bit in number of samples. | |
270 | self.bit_width = float(self.samplerate) / float(self.baudrate) | |
271 | ||
272 | def report(self): | |
273 | pass | |
274 | ||
275 | # Return true if we reached the middle of the desired bit, false otherwise. | |
276 | def reached_bit(self, bitnum): | |
277 | # bitpos is the samplenumber which is in the middle of the | |
278 | # specified UART bit (0 = start bit, 1..x = data, x+1 = parity bit | |
279 | # (if used) or the first stop bit, and so on). | |
280 | bitpos = self.frame_start + (self.bit_width / 2.0) | |
281 | bitpos += bitnum * self.bit_width | |
282 | if self.samplenum >= bitpos: | |
283 | return True | |
284 | return False | |
285 | ||
286 | def reached_bit_last(self, bitnum): | |
287 | bitpos = self.frame_start + ((bitnum + 1) * self.bit_width) | |
288 | if self.samplenum >= bitpos: | |
289 | return True | |
290 | return False | |
291 | ||
292 | def wait_for_start_bit(self, old_signal, signal): | |
293 | # The start bit is always 0 (low). As the idle UART (and the stop bit) | |
294 | # level is 1 (high), the beginning of a start bit is a falling edge. | |
295 | if not (old_signal == 1 and signal == 0): | |
296 | return | |
297 | ||
298 | # Save the sample number where the start bit begins. | |
299 | self.frame_start = self.samplenum | |
300 | ||
301 | self.staterx = GET_START_BIT | |
302 | ||
303 | def get_start_bit(self, signal): | |
304 | # Skip samples until we're in the middle of the start bit. | |
305 | if not self.reached_bit(0): | |
306 | return | |
307 | ||
308 | self.startbit = signal | |
309 | ||
310 | # The startbit must be 0. If not, we report an error. | |
311 | if self.startbit != 0: | |
312 | self.put(self.frame_start, self.samplenum, self.out_proto, | |
313 | [T_INVALID_START, self.startbit]) | |
314 | # TODO: Abort? Ignore rest of the frame? | |
315 | ||
316 | self.cur_data_bit = 0 | |
317 | self.databyte = 0 | |
318 | self.startsample = -1 | |
319 | ||
320 | self.staterx = GET_DATA_BITS | |
321 | ||
322 | self.put(self.frame_start, self.samplenum, self.out_proto, | |
323 | [T_START, self.startbit]) | |
324 | self.put(self.frame_start, self.samplenum, self.out_ann, | |
325 | [ANN_ASCII, ['Start bit', 'Start', 'S']]) | |
326 | ||
327 | def get_data_bits(self, signal): | |
328 | # Skip samples until we're in the middle of the desired data bit. | |
329 | if not self.reached_bit(self.cur_data_bit + 1): | |
330 | return | |
331 | ||
332 | # Save the sample number where the data byte starts. | |
333 | if self.startsample == -1: | |
334 | self.startsample = self.samplenum | |
335 | ||
336 | # Get the next data bit in LSB-first or MSB-first fashion. | |
337 | if self.bit_order == LSB_FIRST: | |
338 | self.databyte >>= 1 | |
339 | self.databyte |= (signal << (self.num_data_bits - 1)) | |
340 | elif self.bit_order == MSB_FIRST: | |
341 | self.databyte <<= 1 | |
342 | self.databyte |= (signal << 0) | |
343 | else: | |
344 | raise Exception('Invalid bit order value: %d', self.bit_order) | |
345 | ||
346 | # Return here, unless we already received all data bits. | |
347 | if self.cur_data_bit < self.num_data_bits - 1: # TODO? Off-by-one? | |
348 | self.cur_data_bit += 1 | |
349 | return | |
350 | ||
351 | self.staterx = GET_PARITY_BIT | |
352 | ||
353 | self.put(self.startsample, self.samplenum - 1, self.out_proto, | |
354 | [T_DATA, self.databyte]) | |
355 | ||
356 | self.put(self.startsample, self.samplenum - 1, self.out_ann, | |
357 | [ANN_ASCII, [chr(self.databyte)]]) | |
358 | self.put(self.startsample, self.samplenum - 1, self.out_ann, | |
359 | [ANN_DEC, [str(self.databyte)]]) | |
360 | self.put(self.startsample, self.samplenum - 1, self.out_ann, | |
361 | [ANN_HEX, [hex(self.databyte), hex(self.databyte)[2:]]]) | |
362 | self.put(self.startsample, self.samplenum - 1, self.out_ann, | |
363 | [ANN_OCT, [oct(self.databyte), oct(self.databyte)[2:]]]) | |
364 | self.put(self.startsample, self.samplenum - 1, self.out_ann, | |
365 | [ANN_BITS, [bin(self.databyte), bin(self.databyte)[2:]]]) | |
366 | ||
367 | def get_parity_bit(self, signal): | |
368 | # If no parity is used/configured, skip to the next state immediately. | |
369 | if self.parity == PARITY_NONE: | |
370 | self.staterx = GET_STOP_BITS | |
371 | return | |
372 | ||
373 | # Skip samples until we're in the middle of the parity bit. | |
374 | if not self.reached_bit(self.num_data_bits + 1): | |
375 | return | |
376 | ||
377 | self.paritybit = signal | |
378 | ||
379 | self.staterx = GET_STOP_BITS | |
380 | ||
381 | if parity_ok(self.parity, self.paritybit, self.databyte, | |
382 | self.num_data_bits): | |
383 | # TODO: Fix range. | |
384 | self.put(self.samplenum, self.samplenum, self.out_proto, | |
385 | [T_PARITY_BIT, self.paritybit]) | |
386 | self.put(self.samplenum, self.samplenum, self.out_ann, | |
387 | [ANN_ASCII, ['Parity bit', 'Parity', 'P']]) | |
388 | else: | |
389 | # TODO: Fix range. | |
390 | # TODO: Return expected/actual parity values. | |
391 | self.put(self.samplenum, self.samplenum, self.out_proto, | |
392 | [T_PARITY_ERROR, (0, 1)]) # FIXME: Dummy tuple... | |
393 | self.put(self.samplenum, self.samplenum, self.out_ann, | |
394 | [ANN_ASCII, ['Parity error', 'Parity err', 'PE']]) | |
395 | ||
396 | # TODO: Currently only supports 1 stop bit. | |
397 | def get_stop_bits(self, signal): | |
398 | # Skip samples until we're in the middle of the stop bit(s). | |
399 | skip_parity = 0 if self.parity == PARITY_NONE else 1 | |
400 | if not self.reached_bit(self.num_data_bits + 1 + skip_parity): | |
401 | return | |
402 | ||
403 | self.stopbit1 = signal | |
404 | ||
405 | # Stop bits must be 1. If not, we report an error. | |
406 | if self.stopbit1 != 1: | |
407 | self.put(self.frame_start, self.samplenum, self.out_proto, | |
408 | [T_INVALID_STOP, self.stopbit1]) | |
409 | # TODO: Abort? Ignore the frame? Other? | |
410 | ||
411 | self.staterx = WAIT_FOR_START_BIT | |
412 | ||
413 | # TODO: Fix range. | |
414 | self.put(self.samplenum, self.samplenum, self.out_proto, | |
415 | [T_STOP, self.stopbit1]) | |
416 | self.put(self.samplenum, self.samplenum, self.out_ann, | |
417 | [ANN_ASCII, ['Stop bit', 'Stop', 'P']]) | |
418 | ||
419 | def decode(self, ss, es, data): # TODO | |
420 | # for (samplenum, (rx, tx)) in data: | |
421 | for (samplenum, (rx,)) in data: | |
422 | ||
423 | # TODO: Start counting at 0 or 1? Increase before or after? | |
424 | self.samplenum += 1 | |
425 | ||
426 | # First sample: Save RX/TX value. | |
427 | if self.oldrx == None: | |
428 | # Get RX/TX bit values (0/1 for low/high) of the first sample. | |
429 | self.oldrx = rx | |
430 | # self.oldtx = tx | |
431 | continue | |
432 | ||
433 | # State machine. | |
434 | if self.staterx == WAIT_FOR_START_BIT: | |
435 | self.wait_for_start_bit(self.oldrx, rx) | |
436 | elif self.staterx == GET_START_BIT: | |
437 | self.get_start_bit(rx) | |
438 | elif self.staterx == GET_DATA_BITS: | |
439 | self.get_data_bits(rx) | |
440 | elif self.staterx == GET_PARITY_BIT: | |
441 | self.get_parity_bit(rx) | |
442 | elif self.staterx == GET_STOP_BITS: | |
443 | self.get_stop_bits(rx) | |
444 | else: | |
445 | raise Exception('Invalid state: %s' % self.staterx) | |
446 | ||
447 | # Save current RX/TX values for the next round. | |
448 | self.oldrx = rx | |
449 | # self.oldtx = tx | |
450 | ||
451 | # if proto != []: | |
452 | # self.put(0, 0, self.out_proto, proto) | |
453 | # if ann != []: | |
454 | # self.put(0, 0, self.out_ann, ann) | |
455 |