2 ## This file is part of the libsigrokdecode project.
4 ## Copyright (C) 2020 Gerhard Sittig <gerhard.sittig@gmx.net>
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.
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.
16 ## You should have received a copy of the GNU General Public License
17 ## along with this program; if not, see <http://www.gnu.org/licenses/>.
20 # See the https://www.pjon.org/ PJON project page and especially the
21 # https://www.pjon.org/PJON-protocol-specification-v3.2.php protocol
22 # specification, which can use different link layers.
25 # - Check for the correct order of optional fields (the spec is not as
26 # explicit on these details as I'd expect).
27 # - Check decoder's robustness, completeness, and correctness when more
28 # captures become available. Currently there are only few, which only
29 # cover minimal communication, and none of the protocol's flexibility.
30 # The decoder was essentially written based on the available docs, and
31 # then took some arbitrary choices and liberties to cope with real life
32 # data from an example setup. Strictly speaking this decoder violates
33 # the spec, and errs towards the usability side.
35 import sigrokdecode as srd
38 ANN_RX_INFO, ANN_HDR_CFG, ANN_PKT_LEN, ANN_META_CRC, ANN_TX_INFO, \
39 ANN_SVC_ID, ANN_PKT_ID, ANN_ANON_DATA, ANN_PAYLOAD, ANN_END_CRC, \
68 class Decoder(srd.Decoder):
73 desc = 'The PJON protocol.'
75 inputs = ['pjon_link']
77 tags = ['Embedded/industrial']
79 ('rx_info', 'Receiver ID'),
80 ('hdr_cfg', 'Header config'),
81 ('pkt_len', 'Packet length'),
82 ('meta_crc', 'Meta CRC'),
83 ('tx_info', 'Sender ID'),
84 ('port', 'Service ID'),
85 ('pkt_id', 'Packet ID'),
86 ('anon', 'Anonymous data'),
87 ('payload', 'Payload'),
88 ('end_crc', 'End CRC'),
89 ('syn_rsp', 'Sync response'),
90 ('relation', 'Relation'),
91 ('warning', 'Warning'),
94 ('fields', 'Fields', (
95 ANN_RX_INFO, ANN_HDR_CFG, ANN_PKT_LEN, ANN_META_CRC, ANN_TX_INFO,
96 ANN_SVC_ID, ANN_ANON_DATA, ANN_PAYLOAD, ANN_END_CRC, ANN_SYN_RSP,
98 ('relations', 'Relations', (ANN_RELATION,)),
99 ('warnings', 'Warnings', (ANN_WARN,)),
108 def reset_frame(self):
111 self.frame_rx_id = None
112 self.frame_tx_id = None
113 self.frame_payload_text = None
114 self.frame_bytes = None
115 self.frame_has_ack = None
116 self.ack_bytes = None
121 self.out_ann = self.register(srd.OUTPUT_ANN)
123 def putg(self, ss, es, ann, data):
124 self.put(ss, es, self.out_ann, [ann, data])
126 def frame_flush(self):
127 if not self.frame_bytes:
129 if not self.frame_ss or not self.frame_es:
132 # Emit "communication relation" details.
134 if self.frame_rx_id is not None:
135 text.append("RX {}".format(self.frame_rx_id[-1]))
136 if self.frame_tx_id is not None:
137 text.append("TX {}".format(self.frame_tx_id[-1]))
138 if self.frame_payload_text is not None:
139 text.append("DATA {}".format(self.frame_payload_text))
140 if self.frame_has_ack is not None:
141 text.append("ACK {:02x}".format(self.frame_has_ack))
143 text = " - ".join(text)
144 self.putg(self.frame_ss, self.frame_es, ANN_RELATION, [text])
146 def handle_field_get_desc(self, idx = None):
147 '''Lookup description of a PJON frame field.'''
148 if not self.field_desc:
151 idx = self.field_desc_idx
152 if idx >= 0 and idx >= len(self.field_desc):
154 if idx < 0 and abs(idx) > len(self.field_desc):
156 desc = self.field_desc[idx]
159 def handle_field_add_desc(self, fmt, hdl, cls = None):
160 '''Register description for a PJON frame field.'''
163 'width': struct.calcsize(fmt),
167 self.field_desc.append(item)
169 def handle_field_seed_desc(self):
170 '''Seed list of PJON frame fields' descriptions.'''
172 # At the start of a PJON frame, the layout of only two fields
173 # is known. Subsequent fields (their presence, and width) depend
174 # on the content of the header config field.
177 self.handle_field_add_desc('<B', self.handle_field_rx_id, ANN_RX_INFO)
178 self.handle_field_add_desc('<B', self.handle_field_config, ANN_HDR_CFG)
180 self.field_desc_idx = 0
181 self.field_desc_got = 0
185 self.frame_rx_id = None
186 self.frame_is_broadcast = None
187 self.frame_tx_id = None
188 self.frame_payload = None
189 self.frame_payload_text = None
190 self.frame_has_ack = None
192 def handle_field_rx_id(self, b):
193 '''Process receiver ID field of a PJON frame.'''
197 # Provide text presentation, caller emits frame field annotation.
198 if b == 255: # "not assigned"
200 elif b == 0: # "broadcast"
203 id_txt = '{:d}'.format(b)
205 'RX_ID {}'.format(id_txt),
209 # Track RX info for communication relation emission.
210 self.frame_rx_id = (b, id_txt)
211 self.frame_is_broadcast = b == 0
215 def handle_field_config(self, b):
216 '''Process header config field of a PJON frame.'''
218 # Caller provides a list of values. We want a single scalar.
221 # Get the config flags.
222 self.cfg_shared = b & (1 << 0)
223 self.cfg_tx_info = b & (1 << 1)
224 self.cfg_sync_ack = b & (1 << 2)
225 self.cfg_async_ack = b & (1 << 3)
226 self.cfg_port = b & (1 << 4)
227 self.cfg_crc32 = b & (1 << 5)
228 self.cfg_len16 = b & (1 << 6)
229 self.cfg_pkt_id = b & (1 << 7)
231 # Get a textual presentation of the flags.
233 text.append('pkt_id' if self.cfg_pkt_id else '-') # packet number
234 text.append('len16' if self.cfg_len16 else '-') # 16bit length not 8bit
235 text.append('crc32' if self.cfg_crc32 else '-') # 32bit CRC not 8bit
236 text.append('svc_id' if self.cfg_port else '-') # port aka service ID
237 text.append('ack_mode' if self.cfg_async_ack else '-') # async response
238 text.append('ack' if self.cfg_sync_ack else '-') # synchronous response
239 text.append('tx_info' if self.cfg_tx_info else '-')
240 text.append('bus_id' if self.cfg_shared else '-') # "shared" vs "local"
241 text = ' '.join(text)
242 bits = '{:08b}'.format(b)
244 'CFG {:s}'.format(text),
245 'CFG {}'.format(bits),
249 # TODO Come up with the most appropriate phrases for this logic.
250 # Are separate instruction groups with repeated conditions more
251 # readable than one common block which registers fields _and_
252 # updates the overhead size? Or is the latter preferrable due to
253 # easier maintenance and less potential for inconsistency?
255 # Get the size of variable width fields, to calculate the size
256 # of the packet overhead (the part that is not the payload data).
257 # This lets us derive the payload length when we later receive
262 len_fmt = u16_fmt if self.cfg_len16 else u8_fmt
264 crc_fmt = u32_fmt if self.cfg_crc32 else u8_fmt
265 self.cfg_overhead = 0
266 self.cfg_overhead += struct.calcsize(u8_fmt) # receiver ID
267 self.cfg_overhead += struct.calcsize(u8_fmt) # header config
268 self.cfg_overhead += struct.calcsize(len_fmt) # packet length
269 self.cfg_overhead += struct.calcsize(u8_fmt) # initial CRC, always CRC8
270 # TODO Check for completeness and correctness.
272 self.cfg_overhead += struct.calcsize(u32_fmt) # receiver bus
275 self.cfg_overhead += struct.calcsize(u32_fmt) # sender bus
276 self.cfg_overhead += struct.calcsize(u8_fmt) # sender ID
278 self.cfg_overhead += struct.calcsize(u16_fmt) # service ID
280 self.cfg_overhead += struct.calcsize(u16_fmt) # packet ID
281 self.cfg_overhead += struct.calcsize(crc_fmt) # end CRC
283 # Register more frame fields as we learn about their presence and
284 # format. Up to this point only receiver ID and header config were
285 # registered since their layout is fixed.
287 # Packet length and meta CRC are always present but can be of
288 # variable width. Optional fields follow the meta CRC and preceed
289 # the payload bytes. Notice that payload length isn't known here
290 # either, though its position is known already. The packet length
291 # is yet to get received. Subtracting the packet overhead from it
292 # (which depends on the header configuration) will provide that
295 # TODO Check for completeness and correctness.
296 # TODO Optionally fold overhead size arith and field registration
297 # into one block of instructions, to reduce the redundancy in the
298 # condition checks, and raise awareness for incomplete sequences
299 # during maintenance.
300 self.handle_field_add_desc(len_fmt, self.handle_field_pkt_len, ANN_PKT_LEN)
301 self.handle_field_add_desc(u8_fmt, self.handle_field_meta_crc, ANN_META_CRC)
303 self.handle_field_add_desc(bus_fmt, self.handle_field_rx_bus, ANN_ANON_DATA)
306 self.handle_field_add_desc(bus_fmt, self.handle_field_tx_bus, ANN_ANON_DATA)
307 self.handle_field_add_desc(u8_fmt, self.handle_field_tx_id, ANN_ANON_DATA)
309 self.handle_field_add_desc(u16_fmt, ['PORT {:d}', '{:d}'], ANN_ANON_DATA)
311 self.handle_field_add_desc(u16_fmt, ['PKT {:04x}', '{:04x}'], ANN_ANON_DATA)
312 pl_fmt = '>{:d}B'.format(0)
313 self.handle_field_add_desc(pl_fmt, self.handle_field_payload, ANN_PAYLOAD)
314 self.handle_field_add_desc(crc_fmt, self.handle_field_end_crc, ANN_END_CRC)
316 # Emit warning annotations for invalid flag combinations.
318 wants_ack = self.cfg_sync_ack or self.cfg_async_ack
319 if wants_ack and not self.cfg_tx_info:
320 warn_texts.append('ACK request without TX info')
321 if wants_ack and self.frame_is_broadcast:
322 warn_texts.append('ACK request for broadcast')
323 if self.cfg_sync_ack and self.cfg_async_ack:
324 warn_texts.append('sync and async ACK request')
325 if self.cfg_len16 and not self.cfg_crc32:
326 warn_texts.append('extended length needs CRC32')
328 warn_texts = ', '.join(warn_texts)
329 self.putg(self.ann_ss, self.ann_es, ANN_WARN, [warn_texts])
331 # Have the caller emit the annotation for configuration data.
334 def handle_field_pkt_len(self, b):
335 '''Process packet length field of a PJON frame.'''
337 # Caller provides a list of values. We want a single scalar.
340 # The wire communicates the total packet length. Some of it is
341 # overhead (non-payload data), while its volume is variable in
342 # size (dpends on the header configuration).
344 # Derive the payload size from previously observed flags. Update
345 # the previously registered field description (the second last
346 # item in the list, before the end CRC).
349 pl_len = b - self.cfg_overhead
351 if pkt_len not in range(self.cfg_overhead, 65536):
352 warn_texts.append('suspicious packet length')
353 if pkt_len > 15 and not self.cfg_crc32:
354 warn_texts.append('length above 15 needs CRC32')
356 warn_texts.append('suspicious payload length')
359 warn_texts = ', '.join(warn_texts)
360 self.putg(self.ann_ss, self.ann_es, ANN_WARN, [warn_texts])
361 pl_fmt = '>{:d}B'.format(pl_len)
363 desc = self.handle_field_get_desc(-2)
364 desc['format'] = pl_fmt
365 desc['width'] = struct.calcsize(pl_fmt)
367 # Have the caller emit the annotation for the packet length.
368 # Provide information of different detail level for zooming.
370 'LENGTH {:d} (PAYLOAD {:d})'.format(pkt_len, pl_len),
371 'LEN {:d} (PL {:d})'.format(pkt_len, pl_len),
372 '{:d} ({:d})'.format(pkt_len, pl_len),
373 '{:d}'.format(pkt_len),
377 def handle_field_common_crc(self, have, is_meta):
378 '''Process a CRC field of a PJON frame.'''
380 # CRC algorithm and width are configurable, and can differ
381 # across meta and end checksums in a frame's fields.
382 caption = 'META' if is_meta else 'END'
383 crc_len = 8 if is_meta else 32 if self.cfg_crc32 else 8
384 crc_fmt = '{:08x}' if crc_len == 32 else '{:02x}'
385 have_text = crc_fmt.format(have)
387 # Check received against expected checksum. Emit warnings.
389 data = self.frame_bytes[:-1]
390 want = calc_crc32(data) if crc_len == 32 else calc_crc8(data)
392 want_text = crc_fmt.format(want)
393 warn_texts.append('CRC mismatch - want {} have {}'.format(want_text, have_text))
395 warn_texts = ', '.join(warn_texts)
396 self.putg(self.ann_ss, self.ann_es, ANN_WARN, [warn_texts])
398 # Provide text representation for frame field, caller emits
401 '{}_CRC {}'.format(caption, have_text),
402 'CRC {}'.format(have_text),
407 def handle_field_meta_crc(self, b):
408 '''Process initial CRC (meta) field of a PJON frame.'''
409 # Caller provides a list of values. We want a single scalar.
411 return self.handle_field_common_crc(b, True)
413 def handle_field_end_crc(self, b):
414 '''Process end CRC (total frame) field of a PJON frame.'''
415 # Caller provides a list of values. We want a single scalar.
417 return self.handle_field_common_crc(b, False)
419 def handle_field_common_bus(self, b):
420 '''Common handling of bus ID details. Used for RX and TX.'''
422 bus_num = struct.unpack('>L', bytearray(bus_id))
423 bus_txt = '.'.join(['{:d}'.format(b) for b in bus_id])
424 return bus_num, bus_txt
426 def handle_field_rx_bus(self, b):
427 '''Process receiver bus ID field of a PJON frame.'''
429 # When we get here, there always should be an RX ID already.
430 bus_num, bus_txt = self.handle_field_common_bus(b[:4])
431 rx_txt = "{} {}".format(bus_txt, self.frame_rx_id[-1])
432 self.frame_rx_id = (bus_num, self.frame_rx_id[0], rx_txt)
434 # Provide text representation for frame field, caller emits
437 'RX_BUS {}'.format(bus_txt),
442 def handle_field_tx_bus(self, b):
443 '''Process transmitter bus ID field of a PJON frame.'''
445 # The TX ID field is optional, as is the use of bus ID fields.
446 # In the TX info case the TX bus ID is seen before the TX ID.
447 bus_num, bus_txt = self.handle_field_common_bus(b[:4])
448 self.frame_tx_id = (bus_num, None, bus_txt)
450 # Provide text representation for frame field, caller emits
453 'TX_BUS {}'.format(bus_txt),
458 def handle_field_tx_id(self, b):
459 '''Process transmitter ID field of a PJON frame.'''
463 id_txt = "{:d}".format(b)
464 if self.frame_tx_id is None:
465 self.frame_tx_id = (b, id_txt)
467 tx_txt = "{} {}".format(self.frame_tx_id[-1], id_txt)
468 self.frame_tx_id = (self.frame_tx_id[0], b, tx_txt)
470 # Provide text representation for frame field, caller emits
473 'TX_ID {}'.format(id_txt),
478 def handle_field_payload(self, b):
479 '''Process payload data field of a PJON frame.'''
481 text = ' '.join(['{:02x}'.format(v) for v in b])
482 self.frame_payload = b[:]
483 self.frame_payload_text = text
486 'PAYLOAD {}'.format(text),
491 def handle_field_sync_resp(self, b):
492 '''Process synchronous response for a PJON frame.'''
494 self.frame_has_ack = b
497 'ACK {:02x}'.format(b),
502 def decode(self, ss, es, data):
505 # Start frame bytes accumulation when FRAME_INIT is seen. Flush
506 # previously accumulated frame bytes when a new frame starts.
507 if ptype == 'FRAME_INIT':
510 self.frame_bytes = []
511 self.handle_field_seed_desc()
516 # Use IDLE as another (earlier) trigger to flush frames. Also
517 # trigger flushes on FRAME-DATA which mean that the link layer
518 # inspection has seen the end of a protocol frame.
520 # TODO Improve usability? Emit warnings for PJON frames where
521 # FRAME_DATA was seen but FRAME_INIT wasn't? So that users can
522 # become aware of broken frames.
523 if ptype in ('IDLE', 'FRAME_DATA'):
528 # Switch from data bytes to response bytes when WAIT is seen.
529 if ptype == 'SYNC_RESP_WAIT':
531 self.ann_ss, self.ann_es = None, None
534 # Accumulate data bytes as they arrive. Put them in the bucket
535 # which corresponds to its most recently seen leader.
536 if ptype == 'DATA_BYTE':
540 # Are we collecting response bytes (ACK)?
541 if self.ack_bytes is not None:
544 self.ack_bytes.append(b)
546 text = self.handle_field_sync_resp(b)
548 self.putg(self.ann_ss, self.ann_es, ANN_SYN_RSP, text)
549 self.ann_ss, self.ann_es = None, None
552 # Are we collecting frame content?
553 if self.frame_bytes is not None:
556 self.frame_bytes.append(b)
559 # Has the field value become available yet?
560 desc = self.handle_field_get_desc()
563 width = desc.get('width', None)
566 self.field_desc_got += 1
567 if self.field_desc_got != width:
570 # Grab most recent received field as a byte array. Get
571 # the values that it contains.
572 fmt = desc.get('format', '>B')
573 raw = bytearray(self.frame_bytes[-width:])
574 values = struct.unpack(fmt, raw)
576 # Process the value, and get its presentation. Can be
577 # mere formatting, or serious execution of logic.
578 hdl = desc.get('handler', '{!r}')
579 if isinstance(hdl, str):
580 text = [hdl.format(*values)]
581 elif isinstance(hdl, (list, tuple)):
582 text = [f.format(*values) for f in hdl]
585 cls = desc.get('anncls', ANN_ANON_DATA)
587 # Emit annotation unless the handler routine already did.
588 if cls is not None and text:
589 self.putg(self.ann_ss, self.ann_es, cls, text)
590 self.ann_ss, self.ann_es = None, None
592 # Advance scan position for to-get-received field.
593 self.field_desc_idx += 1
594 self.field_desc_got = 0
597 # Unknown phase, not collecting. Not synced yet to the input?
600 # Unknown or unhandled kind of link layer output.