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27186eda GS |
1 | /* |
2 | * This file is part of the libsigrok project. | |
3 | * | |
4 | * Copyright (C) 2012 Alexandru Gagniuc <mr.nuke.me@gmail.com> | |
5 | * Copyright (C) 2014 Aurelien Jacobs <aurel@gnuage.org> | |
6 | * Copyright (C) 2019-2020 Gerhard Sittig <gerhard.sittig@gmx.net> | |
7 | * | |
8 | * This program is free software: you can redistribute it and/or modify | |
9 | * it under the terms of the GNU General Public License as published by | |
10 | * the Free Software Foundation, either version 3 of the License, or | |
11 | * (at your option) any later version. | |
12 | * | |
13 | * This program is distributed in the hope that it will be useful, | |
14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
16 | * GNU General Public License for more details. | |
17 | * | |
18 | * You should have received a copy of the GNU General Public License | |
19 | * along with this program. If not, see <http://www.gnu.org/licenses/>. | |
20 | */ | |
21 | ||
22 | /** | |
23 | * @file | |
24 | * | |
25 | * Protocol parser for Brymen BM850s DMM packets. The USB protocol (for the | |
26 | * cable) and the packet description (for the meter) were retrieved from: | |
27 | * http://brymen.com/product-html/Download2.html | |
28 | * http://brymen.com/product-html/PD02BM850s_protocolDL.html | |
29 | * http://brymen.com/product-html/images/DownloadList/ProtocolList/BM850-BM850a-BM850s_List/BM850-BM850a-BM850s-500000-count-DMM-protocol-BC85X-BC85Xa.zip | |
30 | * | |
31 | * Implementor's notes on the protocol: | |
32 | * - The BM85x devices require a low RTS pulse after COM port open and | |
33 | * before communication of requests and responses. The vendor doc | |
34 | * recommends 100ms pulse width including delays around it. Without | |
35 | * that RTS pulse the meter won't respond to requests. | |
36 | * - The request has a three byte header (DLE, STX, command code), two | |
37 | * bytes command arguments, and three bytes tail (checksum, DLE, ETX). | |
38 | * The checksum spans the area (including) the command code and args. | |
39 | * The checksum value is the XOR across all payload bytes. Exclusively | |
40 | * command 0x00 is used (initiate next measurement response) which does | |
41 | * not need arguments (passes all-zero values). | |
42 | * - The response has a four byte header (DLE, STX, command code, payload | |
43 | * size), the respective number of payload data bytes, and a three byte | |
44 | * tail (checksum, DLE, ETX). The checksum spans the range after the | |
45 | * length field and before the checksum field. Command 0 response data | |
46 | * payload consists of a four byte flags field and a text field for | |
47 | * measurement values (floating point with exponent in ASCII). | |
48 | * - Special cases of response data: | |
49 | * - The text field which carries the measurement value also contains | |
50 | * whitespace which may break simple text to number conversion. Like | |
51 | * 10 02 00 0f 07 00 00 00 20 30 2e 30 30 33 32 20 45 2b 30 46 10 03 | |
52 | * which translates to: 07 00 00 00 " 0.0032 E+0". Text for overload | |
53 | * conditions can be shorter which results in variable packet length. | |
54 | * Some meter functions provide unexpected text for their values. | |
55 | * - The reference impedance for decibel measurements looks wrong and | |
56 | * requires special treatment to isolate the 4..1200R value: | |
57 | * bfunc 80 20 00 00, text " 0. 800 E+1" (reference, 800R) | |
58 | * The decibel measurement values use an unexpected scale. | |
59 | * bfunc 00 20 00 00, text "-0.3702 E-1" (measurement, -37.02dBm) | |
60 | * The reference value gets sent (sometimes) in a DMM response when | |
61 | * the meter's function is entered, or the reference value changes. | |
62 | * The 'bfunc' flags combination allows telling packet types apart. | |
63 | * - Temperature measurements put the C/F unit between the mantissa | |
64 | * and the exponent, which needs to get removed: " 0.0217CE+3" | |
65 | * - Diode measurements appear to exclusively provide the 'Volt' flag | |
66 | * but no 'Diode' flag. The display shows ".diod" for a moment but | |
67 | * this information is no longer available when voltage measurements | |
68 | * are seen. | |
69 | */ | |
70 | ||
71 | #include <config.h> | |
72 | #include <ctype.h> | |
73 | #include <math.h> | |
74 | #include <libsigrok/libsigrok.h> | |
75 | #include "libsigrok-internal.h" | |
76 | #include <string.h> | |
77 | ||
78 | #define LOG_PREFIX "brymen-bm85x" | |
79 | ||
80 | #define STX 0x02 | |
81 | #define ETX 0x03 | |
82 | #define DLE 0x10 | |
83 | ||
84 | #define CMD_GET_READING 0 | |
85 | ||
86 | #define PKT_HEAD_LEN 4 | |
87 | #define PKT_DATA_MAX 15 | |
88 | #define PKT_TAIL_LEN 3 | |
89 | #define PKT_BFUNC_LEN 4 | |
90 | ||
91 | static uint8_t bm85x_crc(const uint8_t *buf, size_t len) | |
92 | { | |
93 | uint8_t crc; | |
94 | ||
95 | crc = 0; | |
96 | while (len--) | |
97 | crc ^= *buf++; | |
98 | ||
99 | return crc; | |
100 | } | |
101 | ||
102 | #ifdef HAVE_SERIAL_COMM | |
103 | /** Meter's specific activity after port open and before data exchange. */ | |
104 | SR_PRIV int brymen_bm85x_after_open(struct sr_serial_dev_inst *serial) | |
105 | { | |
106 | int rts_toggle_delay_us; | |
107 | ||
108 | /* | |
109 | * The device requires an RTS *pulse* before communication. | |
110 | * The vendor's documentation recommends the following sequence: | |
111 | * Open the COM port, wait for 100ms, set RTS=1, wait for 100ms, | |
112 | * set RTS=0, wait for 100ms, set RTS=1, configure bitrate and | |
113 | * frame format, transmit request data, receive response data. | |
114 | */ | |
115 | rts_toggle_delay_us = 100 * 1000; /* 100ms */ | |
116 | g_usleep(rts_toggle_delay_us); | |
117 | serial_set_handshake(serial, 1, -1); | |
118 | g_usleep(rts_toggle_delay_us); | |
119 | serial_set_handshake(serial, 0, -1); | |
120 | g_usleep(rts_toggle_delay_us); | |
121 | serial_set_handshake(serial, 1, -1); | |
122 | g_usleep(rts_toggle_delay_us); | |
123 | ||
124 | return SR_OK; | |
125 | } | |
126 | ||
127 | static int bm85x_send_command(struct sr_serial_dev_inst *serial, | |
128 | uint8_t cmd, uint8_t arg1, uint8_t arg2) | |
129 | { | |
130 | uint8_t buf[8]; | |
131 | uint8_t crc, *wrptr, *crcptr; | |
132 | size_t wrlen; | |
133 | int ret; | |
134 | ||
135 | wrptr = &buf[0]; | |
136 | write_u8_inc(&wrptr, DLE); | |
137 | write_u8_inc(&wrptr, STX); | |
138 | crcptr = wrptr; | |
139 | write_u8_inc(&wrptr, cmd); | |
140 | write_u8_inc(&wrptr, arg1); | |
141 | write_u8_inc(&wrptr, arg2); | |
142 | crc = bm85x_crc(crcptr, wrptr - crcptr); | |
143 | write_u8_inc(&wrptr, crc); | |
144 | write_u8_inc(&wrptr, DLE); | |
145 | write_u8_inc(&wrptr, ETX); | |
146 | ||
147 | wrlen = wrptr - &buf[0]; | |
148 | ret = serial_write_nonblocking(serial, &buf[0], wrlen); | |
149 | if (ret < 0) | |
150 | return ret; | |
151 | if ((size_t)ret != wrlen) | |
152 | return SR_ERR_IO; | |
153 | ||
154 | return SR_OK; | |
155 | } | |
156 | ||
157 | /** Initiate reception of another meter's reading. */ | |
158 | SR_PRIV int brymen_bm85x_packet_request(struct sr_serial_dev_inst *serial) | |
159 | { | |
160 | return bm85x_send_command(serial, CMD_GET_READING, 0, 0); | |
161 | } | |
162 | #endif | |
163 | ||
164 | /** | |
165 | * Check Brymen BM85x DMM packet for validity. | |
166 | * | |
167 | * @param[in] st The DMM driver's internal state. | |
168 | * @param[in] buf The data bytes received so far. | |
169 | * @param[in] len The received data's length (byte count). | |
170 | * @param[out] pkt_len The packet's calculated total size (when valid). | |
171 | * | |
172 | * The BM850s protocol uses packets of variable length. A minimum amount | |
173 | * of RX data provides the packet header, which communicates the payload | |
174 | * size, which allows to determine the packet's total size. Callers of | |
175 | * this validity checker can learn how much data will get consumed when | |
176 | * a valid packet got received and processed. The packet size is not | |
177 | * known in advance. | |
178 | * | |
179 | * @returns SR_OK when the packet is valid. | |
180 | * @returns SR_ERR* (below zero) when the packet is invalid. | |
181 | * @returns Greater 0 when packet is incomplete, more data is needed. | |
182 | */ | |
183 | SR_PRIV int brymen_bm85x_packet_valid(void *st, | |
184 | const uint8_t *buf, size_t len, size_t *pkt_len) | |
185 | { | |
186 | size_t plen; | |
187 | uint8_t cmd, crc; | |
188 | ||
189 | (void)st; | |
190 | ||
191 | /* Four header bytes: DLE, STX, command, payload length. */ | |
192 | if (len < PKT_HEAD_LEN) | |
193 | return SR_PACKET_NEED_RX; | |
194 | if (read_u8_inc(&buf) != DLE) | |
195 | return SR_PACKET_INVALID; | |
196 | if (read_u8_inc(&buf) != STX) | |
197 | return SR_PACKET_INVALID; | |
198 | cmd = read_u8_inc(&buf); | |
199 | /* Non-fatal, happens with OL pending during connect. */ | |
200 | if (cmd == 0x01) | |
201 | cmd = 0x00; | |
202 | if (cmd != CMD_GET_READING) | |
203 | return SR_PACKET_INVALID; | |
204 | plen = read_u8_inc(&buf); | |
205 | if (plen > PKT_DATA_MAX) | |
206 | return SR_PACKET_INVALID; | |
207 | len -= PKT_HEAD_LEN; | |
208 | ||
209 | /* Checksum spans bfunc and value text. Length according to header. */ | |
210 | if (len < plen + PKT_TAIL_LEN) | |
211 | return SR_PACKET_NEED_RX; | |
212 | crc = bm85x_crc(buf, plen); | |
213 | buf += plen; | |
214 | len -= plen; | |
215 | ||
216 | /* Three tail bytes: checksum, DLE, ETX. */ | |
217 | if (len < PKT_TAIL_LEN) | |
218 | return SR_PACKET_NEED_RX; | |
219 | if (read_u8_inc(&buf) != crc) | |
220 | return SR_PACKET_INVALID; | |
221 | if (read_u8_inc(&buf) != DLE) | |
222 | return SR_PACKET_INVALID; | |
223 | if (read_u8_inc(&buf) != ETX) | |
224 | return SR_PACKET_INVALID; | |
225 | ||
226 | /* | |
227 | * Only return the total packet length when the receive buffer | |
228 | * was found to be valid. For invalid packets it's preferred to | |
229 | * have the caller keep trying to sync to the packet stream. | |
230 | */ | |
231 | if (pkt_len) | |
232 | *pkt_len = PKT_HEAD_LEN + plen + PKT_TAIL_LEN; | |
233 | return SR_PACKET_VALID; | |
234 | } | |
235 | ||
236 | struct bm85x_flags { | |
237 | gboolean is_batt, is_db, is_perc, is_hz, is_amp, is_beep; | |
238 | gboolean is_ohm, is_temp_f, is_temp_c, is_diode, is_cap; | |
239 | gboolean is_volt, is_dc, is_ac; | |
240 | }; | |
241 | ||
242 | static int bm85x_parse_flags(const uint8_t *bfunc, struct bm85x_flags *flags) | |
243 | { | |
244 | if (!bfunc || !flags) | |
245 | return SR_ERR_ARG; | |
246 | memset(flags, 0, sizeof(*flags)); | |
247 | ||
248 | flags->is_batt = bfunc[3] & (1u << 7); | |
249 | if ((bfunc[3] & 0x7f) != 0) | |
250 | return SR_ERR_ARG; | |
251 | ||
252 | if ((bfunc[2] & 0xff) != 0) | |
253 | return SR_ERR_ARG; | |
254 | ||
255 | if ((bfunc[1] & 0xc0) != 0) | |
256 | return SR_ERR_ARG; | |
257 | flags->is_db = bfunc[1] & (1u << 5); | |
258 | if ((bfunc[1] & 0x10) != 0) | |
259 | return SR_ERR_ARG; | |
260 | flags->is_perc = bfunc[1] & (1u << 3); | |
261 | flags->is_hz = bfunc[1] & (1u << 2); | |
262 | flags->is_amp = bfunc[1] & (1u << 1); | |
263 | flags->is_beep = bfunc[1] & (1u << 0); | |
264 | ||
265 | flags->is_ohm = bfunc[0] & (1u << 7); | |
266 | flags->is_temp_f = bfunc[0] & (1u << 6); | |
267 | flags->is_temp_c = bfunc[0] & (1u << 5); | |
268 | flags->is_diode = bfunc[0] & (1u << 4); | |
269 | flags->is_cap = bfunc[0] & (1u << 3); | |
270 | flags->is_volt = bfunc[0] & (1u << 2); | |
271 | flags->is_dc = bfunc[0] & (1u << 1); | |
272 | flags->is_ac = bfunc[0] & (1u << 0); | |
273 | ||
274 | return SR_OK; | |
275 | } | |
276 | ||
277 | static int bm85x_parse_value(char *txt, double *val, int *digits) | |
278 | { | |
279 | char *src, *dst, c; | |
280 | int ret; | |
281 | ||
282 | /* | |
283 | * See above comment on whitespace in response's number text. | |
284 | * The caller provides a NUL terminated writable text copy. | |
285 | * Go for low hanging fruit first (OL condition). Eliminate | |
286 | * whitespace then and do the number conversion. | |
287 | */ | |
288 | if (strstr(txt, "+OL")) { | |
289 | *val = +INFINITY; | |
290 | return SR_OK; | |
291 | } | |
292 | if (strstr(txt, "-OL")) { | |
293 | *val = -INFINITY; | |
294 | return SR_OK; | |
295 | } | |
296 | if (strstr(txt, "OL")) { | |
297 | *val = INFINITY; | |
298 | return SR_OK; | |
299 | } | |
300 | ||
301 | src = txt; | |
302 | dst = txt; | |
303 | while (*src) { | |
304 | c = *src++; | |
305 | if (c == ' ') | |
306 | continue; | |
307 | *dst++ = c; | |
308 | } | |
309 | *dst = '\0'; | |
310 | ||
311 | ret = sr_atod_ascii_digits(txt, val, digits); | |
312 | if (ret != SR_OK) | |
313 | return ret; | |
314 | ||
315 | return SR_OK; | |
316 | } | |
317 | ||
318 | static int bm85x_parse_payload(const uint8_t *p, size_t l, | |
319 | double *val, struct sr_datafeed_analog *analog) | |
320 | { | |
321 | const uint8_t *bfunc; | |
322 | char text_buf[PKT_DATA_MAX], *text; | |
323 | size_t text_len; | |
324 | int ret; | |
325 | struct bm85x_flags flags; | |
326 | int digits; | |
327 | char *parse; | |
328 | ||
329 | /* Get a bfunc bits reference, and a writable value text. */ | |
330 | bfunc = &p[0]; | |
331 | text_len = l - PKT_BFUNC_LEN; | |
332 | memcpy(text_buf, &p[PKT_BFUNC_LEN], text_len); | |
333 | text_buf[text_len] = '\0'; | |
334 | text = &text_buf[0]; | |
335 | sr_dbg("DMM bfunc %02x %02x %02x %02x, text \"%s\"", | |
336 | bfunc[0], bfunc[1], bfunc[2], bfunc[3], text); | |
337 | ||
338 | /* Check 'bfunc' bitfield first, text interpretation depends on it. */ | |
339 | ret = bm85x_parse_flags(bfunc, &flags); | |
340 | if (ret != SR_OK) | |
341 | return ret; | |
342 | ||
343 | /* Parse the text after potential normalization/transformation. */ | |
344 | if (flags.is_db && flags.is_ohm) { | |
345 | static const char *prefix = " 0."; | |
346 | static const char *suffix = " E"; | |
347 | /* See above comment on dBm reference value text. */ | |
348 | if (strncmp(text, prefix, strlen(prefix)) != 0) | |
349 | return SR_ERR_DATA; | |
350 | text += strlen(prefix); | |
351 | text_len -= strlen(prefix); | |
352 | parse = strstr(text, suffix); | |
353 | if (!parse) | |
354 | return SR_ERR_DATA; | |
355 | *parse = '\0'; | |
356 | } | |
357 | if (flags.is_temp_f || flags.is_temp_c) { | |
358 | /* See above comment on temperature value text. */ | |
359 | parse = strchr(text, flags.is_temp_f ? 'F' : 'C'); | |
360 | if (!parse) | |
361 | return SR_ERR_DATA; | |
362 | *parse = ' '; | |
363 | } | |
364 | digits = 0; | |
365 | ret = bm85x_parse_value(text, val, &digits); | |
366 | if (ret != SR_OK) | |
367 | return ret; | |
368 | ||
369 | /* Fill in MQ and flags result details. */ | |
370 | analog->meaning->mqflags = 0; | |
371 | if (flags.is_volt) { | |
372 | analog->meaning->mq = SR_MQ_VOLTAGE; | |
373 | analog->meaning->unit = SR_UNIT_VOLT; | |
374 | } | |
375 | if (flags.is_amp) { | |
376 | analog->meaning->mq = SR_MQ_CURRENT; | |
377 | analog->meaning->unit = SR_UNIT_AMPERE; | |
378 | } | |
379 | if (flags.is_ohm) { | |
380 | if (flags.is_db) | |
381 | analog->meaning->mq = SR_MQ_RESISTANCE; | |
382 | else if (flags.is_beep) | |
383 | analog->meaning->mq = SR_MQ_CONTINUITY; | |
384 | else | |
385 | analog->meaning->mq = SR_MQ_RESISTANCE; | |
386 | analog->meaning->unit = SR_UNIT_OHM; | |
387 | } | |
388 | if (flags.is_hz) { | |
389 | analog->meaning->mq = SR_MQ_FREQUENCY; | |
390 | analog->meaning->unit = SR_UNIT_HERTZ; | |
391 | } | |
392 | if (flags.is_perc) { | |
393 | analog->meaning->mq = SR_MQ_DUTY_CYCLE; | |
394 | analog->meaning->unit = SR_UNIT_PERCENTAGE; | |
395 | } | |
396 | if (flags.is_cap) { | |
397 | analog->meaning->mq = SR_MQ_CAPACITANCE; | |
398 | analog->meaning->unit = SR_UNIT_FARAD; | |
399 | } | |
400 | if (flags.is_temp_f) { | |
401 | analog->meaning->mq = SR_MQ_TEMPERATURE; | |
402 | analog->meaning->unit = SR_UNIT_FAHRENHEIT; | |
403 | } | |
404 | if (flags.is_temp_c) { | |
405 | analog->meaning->mq = SR_MQ_TEMPERATURE; | |
406 | analog->meaning->unit = SR_UNIT_CELSIUS; | |
407 | } | |
408 | if (flags.is_db && !flags.is_ohm) { | |
409 | /* See above comment on dBm measurements scale. */ | |
410 | analog->meaning->mq = SR_MQ_POWER; | |
411 | analog->meaning->unit = SR_UNIT_DECIBEL_MW; | |
412 | *val *= 1000; | |
413 | digits -= 3; | |
414 | } | |
415 | ||
416 | if (flags.is_diode) { | |
417 | /* See above comment on diode measurement responses. */ | |
418 | analog->meaning->mq = SR_MQ_VOLTAGE; | |
419 | analog->meaning->unit = SR_UNIT_VOLT; | |
420 | analog->meaning->mqflags |= SR_MQFLAG_DIODE; | |
421 | analog->meaning->mqflags |= SR_MQFLAG_DC; | |
422 | } | |
423 | if (flags.is_ac) | |
424 | analog->meaning->mqflags |= SR_MQFLAG_AC; | |
425 | if (flags.is_dc) | |
426 | analog->meaning->mqflags |= SR_MQFLAG_DC; | |
427 | ||
428 | analog->encoding->digits = digits; | |
429 | analog->spec->spec_digits = digits; | |
430 | ||
431 | if (flags.is_batt) | |
432 | sr_warn("Low battery!"); | |
433 | ||
434 | return SR_OK; | |
435 | } | |
436 | ||
437 | SR_PRIV int brymen_bm85x_parse(void *st, const uint8_t *buf, size_t len, | |
438 | double *val, struct sr_datafeed_analog *analog, void *info) | |
439 | { | |
440 | const uint8_t *pl_ptr; | |
441 | size_t pl_len; | |
442 | ||
443 | (void)st; | |
444 | (void)info; | |
445 | ||
446 | if (!buf || !len) | |
447 | return SR_ERR_DATA; | |
448 | if (!val || !analog) | |
449 | return SR_ERR_DATA; | |
450 | ||
451 | if (brymen_bm85x_packet_valid(NULL, buf, len, NULL) != SR_PACKET_VALID) | |
452 | return SR_ERR_DATA; | |
453 | pl_ptr = &buf[PKT_HEAD_LEN]; | |
454 | pl_len = len - PKT_HEAD_LEN - PKT_TAIL_LEN; | |
455 | ||
456 | return bm85x_parse_payload(pl_ptr, pl_len, val, analog); | |
457 | } |