]>
Commit | Line | Data |
---|---|---|
1 | /* | |
2 | * This file is part of the libsigrok project. | |
3 | * | |
4 | * Copyright (C) 2023 Gerhard Sittig <gerhard.sittig@gmx.net> | |
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 3 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, see <http://www.gnu.org/licenses/>. | |
18 | */ | |
19 | ||
20 | /* | |
21 | * Communicate to the Devantech ETH008 relay card via TCP and Ethernet. | |
22 | * | |
23 | * See http://www.robot-electronics.co.uk/files/eth008b.pdf for device | |
24 | * capabilities and a protocol discussion. | |
25 | * See https://github.com/devantech/devantech_eth_python for Python | |
26 | * source code which is maintained by the vendor. The untested parts | |
27 | * of this sigrok driver are based on version 0.1.2 of this Python | |
28 | * code which is MIT licensed (corresponds to commit 0c0080b88e29), | |
29 | * and example code in ZIP archives provided on the shop's products' | |
30 | * pages. | |
31 | * | |
32 | * The device provides several means of communication: HTTP requests | |
33 | * (as well as an interactive web form). Raw TCP communication with | |
34 | * binary requests and responses. Text requests and responses over | |
35 | * TCP sockets. Some of these depend on the firmware version. Version | |
36 | * checks before command transmission is essentially non-existent in | |
37 | * this sigrok driver implementation. Binary transmission is preferred | |
38 | * because it is assumed that this existed in all firmware versions. | |
39 | * The firmware interestingly accepts concurrent network connections | |
40 | * (up to five of them, all share the same password). Which means that | |
41 | * the peripheral's state can change even while we control it. | |
42 | * | |
43 | * It's assumed that WLAN models differ from Ethernet devices in terms | |
44 | * of their hardware, but TCP communication should not bother about the | |
45 | * underlying physics, and WLAN cards can re-use model IDs and firmware | |
46 | * implementations. Given sigrok's abstraction of the serial transport | |
47 | * those cards could also be attached by means of COM ports. | |
48 | * | |
49 | * TCP communication seems to rely on network fragmentation and assumes | |
50 | * that software stacks provide all of a request in a single receive | |
51 | * call on the firmware side. Which works for local communication, but | |
52 | * could become an issue when long distances and tunnels are involved. | |
53 | * This sigrok driver also assumes complete reception within a single | |
54 | * receive call. The short length of binary transmission helps here | |
55 | * (the largest payloads has a length of three bytes). | |
56 | * | |
57 | * The lack of length specs as well as termination in the protocol | |
58 | * (both binary as well as text variants over TCP sockets) results in | |
59 | * the inability to synchronize to the firmware when connecting and | |
60 | * after hiccups in an established connection. The fixed length of | |
61 | * requests and responses for binary payloads helps a little bit, | |
62 | * assuming that TCP connect is used to recover. The overhead of | |
63 | * HTTP requests and responses is considered undesirable for this | |
64 | * sigrok driver implementation. [This also means that a transport | |
65 | * which lacks the concept of network frames cannot send passwords.] | |
66 | * The binary transport appears to lack HELLO or NOP requests that | |
67 | * could be used to synchronize. Firmware just would not respond to | |
68 | * unsupported commands. Maybe a repeated sequence of identity reads | |
69 | * combined with a read timeout could help synchronize, but only if | |
70 | * the response is known because the model was identified before. | |
71 | * | |
72 | * The sigrok driver source code was phrased with the addition of more | |
73 | * models in mind. Only few code paths require adjustment when similar | |
74 | * variants of requests or responses are involved in the communication | |
75 | * to relay cards that support between two and twenty channels. Chances | |
76 | * are good, existing firmware is compatible across firmware versions, | |
77 | * and even across hardware revisions (model upgrades). Firmware just | |
78 | * happens to not respond to unknown requests. | |
79 | * | |
80 | * TODO | |
81 | * - Add support for other models. Currently exclusively supports the | |
82 | * ETH008-B model which was used during implementation of the driver. | |
83 | * (Descriptions for more models were added, their operation is yet | |
84 | * to get verified.) Getting relay state involves variable length | |
85 | * responses, bits appear to be in little endian presentation. | |
86 | * - Add support for absent relay output channels (ETH484 lacks R5..R8). | |
87 | * - Add support for digital inputs. ETH484 has command 0x25 which gets | |
88 | * two bytes, the second byte carries eight digital input bits. | |
89 | * ETH1610 has 16 inputs, evaluates both bytes. Is data format u16be? | |
90 | * ETH8020 support code is inconsistent, implements two accessors | |
91 | * which either retrieve two or three bytes, while callers access the | |
92 | * fourth byte of these responses? Cannot have worked, seems untested. | |
93 | * - Add support for analog inputs. ETH484 has command 0x32 which takes | |
94 | * a channel number, and gets two bytes which carry a u16be value(?). | |
95 | * So does ETH8020. Channel count differs across models. | |
96 | * - Are there other models of interest? ETH1610 product page reads | |
97 | * as if the card had 10 relays (strict output), and 16 inputs which | |
98 | * could either be used in analog mode, or simply get interpreted as | |
99 | * digital input? | |
100 | * - Add support for password protection? | |
101 | * - See command 0x79 to "login" (beware of the differing return value | |
102 | * compared to other commands), command 0x7a to check if passwords | |
103 | * are involved and whether the login needs refreshing, command 0x7b | |
104 | * for immediate "logout" in contrast to expiration. | |
105 | * - Alternatively consider switching to the "text protocol" in that | |
106 | * use case, which can send an optional password in every request | |
107 | * that controls relays (command 0x3a). | |
108 | * - How to specify the password in applications and how to pass them | |
109 | * to this driver is yet another issue that needs consideration. | |
110 | */ | |
111 | ||
112 | #include "config.h" | |
113 | ||
114 | #include <string.h> | |
115 | ||
116 | #include "protocol.h" | |
117 | ||
118 | #define READ_TIMEOUT_MS 20 | |
119 | ||
120 | enum cmd_code { | |
121 | CMD_GET_MODULE_INFO = 0x10, | |
122 | CMD_DIGITAL_ACTIVE = 0x20, | |
123 | CMD_DIGITAL_INACTIVE = 0x21, | |
124 | CMD_DIGITAL_SET_OUTPUTS = 0x23, | |
125 | CMD_DIGITAL_GET_OUTPUTS = 0x24, | |
126 | CMD_DIGITAL_GET_INPUTS = 0x25, | |
127 | CMD_ANALOG_GET_INPUT = 0x32, | |
128 | CMD_ASCII_TEXT_COMMAND = 0x3a, | |
129 | CMD_GET_SERIAL_NUMBER = 0x77, | |
130 | CMD_GET_SUPPLY_VOLTS = 0x78, | |
131 | CMD_PASSWORD_ENTRY = 0x79, | |
132 | CMD_GET_UNLOCK_TIME = 0x7a, | |
133 | CMD_IMMEDIATE_LOGOUT = 0x7b, | |
134 | }; | |
135 | ||
136 | /* | |
137 | * Transmit a request to the relay card. Checks that all bytes get sent, | |
138 | * short writes are considered fatal. | |
139 | */ | |
140 | static int send_request(struct sr_serial_dev_inst *ser, | |
141 | const uint8_t *data, size_t dlen) | |
142 | { | |
143 | int ret; | |
144 | size_t written; | |
145 | ||
146 | if (sr_log_loglevel_get() >= SR_LOG_SPEW) { | |
147 | GString *txt = sr_hexdump_new(data, dlen); | |
148 | sr_spew("TX --> %s.", txt->str); | |
149 | sr_hexdump_free(txt); | |
150 | } | |
151 | ret = serial_write_blocking(ser, data, dlen, 0); | |
152 | if (ret < 0) | |
153 | return ret; | |
154 | written = (size_t)ret; | |
155 | if (written != dlen) | |
156 | return SR_ERR_DATA; | |
157 | return SR_OK; | |
158 | } | |
159 | ||
160 | /* | |
161 | * Receive a response from the relay card. Assumes fixed size payload, | |
162 | * considers short reads fatal. | |
163 | */ | |
164 | static int recv_response(struct sr_serial_dev_inst *ser, | |
165 | uint8_t *data, size_t dlen) | |
166 | { | |
167 | int ret; | |
168 | size_t got; | |
169 | ||
170 | ret = serial_read_blocking(ser, data, dlen, READ_TIMEOUT_MS); | |
171 | if (ret < 0) | |
172 | return ret; | |
173 | got = (size_t)ret; | |
174 | if (sr_log_loglevel_get() >= SR_LOG_SPEW) { | |
175 | GString *txt = sr_hexdump_new(data, got); | |
176 | sr_spew("<-- RX %s.", txt->str); | |
177 | sr_hexdump_free(txt); | |
178 | } | |
179 | if (got != dlen) | |
180 | return SR_ERR_DATA; | |
181 | return SR_OK; | |
182 | } | |
183 | ||
184 | /* Send a request then receive a response. Convenience routine. */ | |
185 | static int send_then_recv(struct sr_serial_dev_inst *serial, | |
186 | const uint8_t *tx_data, size_t tx_length, | |
187 | uint8_t *rx_data, size_t rx_length) | |
188 | { | |
189 | int ret; | |
190 | ||
191 | if (tx_data && tx_length) { | |
192 | ret = send_request(serial, tx_data, tx_length); | |
193 | if (ret != SR_OK) | |
194 | return ret; | |
195 | } | |
196 | ||
197 | if (rx_data && rx_length) { | |
198 | ret = recv_response(serial, rx_data, rx_length); | |
199 | if (ret != SR_OK) | |
200 | return ret; | |
201 | } | |
202 | ||
203 | return SR_OK; | |
204 | } | |
205 | ||
206 | /* Identify the relay card, gather version information details. */ | |
207 | SR_PRIV int devantech_eth008_get_model(struct sr_serial_dev_inst *serial, | |
208 | uint8_t *model_code, uint8_t *hw_version, uint8_t *fw_version) | |
209 | { | |
210 | uint8_t req[1], *wrptr; | |
211 | uint8_t rsp[3], v8; | |
212 | const uint8_t *rdptr; | |
213 | int ret; | |
214 | ||
215 | if (model_code) | |
216 | *model_code = 0; | |
217 | if (hw_version) | |
218 | *hw_version = 0; | |
219 | if (fw_version) | |
220 | *fw_version = 0; | |
221 | ||
222 | wrptr = req; | |
223 | write_u8_inc(&wrptr, CMD_GET_MODULE_INFO); | |
224 | ret = send_then_recv(serial, req, wrptr - req, rsp, sizeof(rsp)); | |
225 | if (ret != SR_OK) | |
226 | return ret; | |
227 | rdptr = rsp; | |
228 | ||
229 | v8 = read_u8_inc(&rdptr); | |
230 | if (model_code) | |
231 | *model_code = v8; | |
232 | v8 = read_u8_inc(&rdptr); | |
233 | if (hw_version) | |
234 | *hw_version = v8; | |
235 | v8 = read_u8_inc(&rdptr); | |
236 | if (fw_version) | |
237 | *fw_version = v8; | |
238 | ||
239 | return SR_OK; | |
240 | } | |
241 | ||
242 | /* Get the relay card's serial number (its MAC address). */ | |
243 | SR_PRIV int devantech_eth008_get_serno(struct sr_serial_dev_inst *serial, | |
244 | char *text_buffer, size_t text_length) | |
245 | { | |
246 | uint8_t req[1], *wrptr; | |
247 | uint8_t rsp[6], b; | |
248 | const uint8_t *rdptr, *endptr; | |
249 | size_t written; | |
250 | int ret; | |
251 | ||
252 | if (text_buffer && !text_length) | |
253 | return SR_ERR_ARG; | |
254 | if (text_buffer) | |
255 | memset(text_buffer, 0, text_length); | |
256 | ||
257 | wrptr = req; | |
258 | write_u8_inc(&wrptr, CMD_GET_SERIAL_NUMBER); | |
259 | ret = send_then_recv(serial, req, wrptr - req, rsp, sizeof(rsp)); | |
260 | if (ret != SR_OK) | |
261 | return ret; | |
262 | rdptr = rsp; | |
263 | ||
264 | endptr = rsp + sizeof(rsp); | |
265 | while (rdptr < endptr && text_buffer && text_length >= 3) { | |
266 | b = read_u8_inc(&rdptr); | |
267 | written = snprintf(text_buffer, text_length, "%02x", b); | |
268 | text_buffer += written; | |
269 | text_length -= written; | |
270 | } | |
271 | ||
272 | return SR_OK; | |
273 | } | |
274 | ||
275 | /* Update an internal cache from the relay card's current state. */ | |
276 | SR_PRIV int devantech_eth008_cache_state(const struct sr_dev_inst *sdi) | |
277 | { | |
278 | struct sr_serial_dev_inst *serial; | |
279 | struct dev_context *devc; | |
280 | size_t rx_size; | |
281 | uint8_t req[1], *wrptr; | |
282 | uint8_t rsp[3]; | |
283 | const uint8_t *rdptr; | |
284 | uint32_t have; | |
285 | int ret; | |
286 | ||
287 | serial = sdi->conn; | |
288 | if (!serial) | |
289 | return SR_ERR_ARG; | |
290 | devc = sdi->priv; | |
291 | if (!devc) | |
292 | return SR_ERR_ARG; | |
293 | ||
294 | /* Get the state of digital outputs when the model supports them. */ | |
295 | if (devc->model->ch_count_do) { | |
296 | rx_size = devc->model->width_do; | |
297 | if (rx_size > sizeof(rsp)) | |
298 | return SR_ERR_NA; | |
299 | ||
300 | wrptr = req; | |
301 | write_u8_inc(&wrptr, CMD_DIGITAL_GET_OUTPUTS); | |
302 | ret = send_then_recv(serial, req, wrptr - req, rsp, rx_size); | |
303 | if (ret != SR_OK) | |
304 | return ret; | |
305 | rdptr = rsp; | |
306 | ||
307 | switch (rx_size) { | |
308 | case 1: | |
309 | have = read_u8_inc(&rdptr); | |
310 | break; | |
311 | case 2: | |
312 | have = read_u16le_inc(&rdptr); | |
313 | break; | |
314 | case 3: | |
315 | have = read_u24le_inc(&rdptr); | |
316 | break; | |
317 | default: | |
318 | return SR_ERR_NA; | |
319 | } | |
320 | have &= devc->mask_do; | |
321 | devc->curr_do = have; | |
322 | } | |
323 | ||
324 | /* | |
325 | * Get the state of digital inputs when the model supports them. | |
326 | * Firmware of other models happens to not respond to unknown | |
327 | * requests. Responses seem to have identical size across all | |
328 | * models. Payload is assumed to be u16 be formatted. Must be | |
329 | * verified when other models are seen. | |
330 | * | |
331 | * Caching the state of analog inputs is condidered undesirable. | |
332 | */ | |
333 | if (devc->model->ch_count_di) { | |
334 | rx_size = sizeof(uint16_t); | |
335 | if (rx_size > sizeof(rsp)) | |
336 | return SR_ERR_NA; | |
337 | ||
338 | wrptr = req; | |
339 | write_u8_inc(&wrptr, CMD_DIGITAL_GET_INPUTS); | |
340 | ret = send_then_recv(serial, req, wrptr - req, rsp, rx_size); | |
341 | if (ret != SR_OK) | |
342 | return ret; | |
343 | rdptr = rsp; | |
344 | ||
345 | switch (rx_size) { | |
346 | case 2: | |
347 | have = read_u16be_inc(&rdptr); | |
348 | break; | |
349 | default: | |
350 | return SR_ERR_NA; | |
351 | } | |
352 | have &= (1UL << devc->model->ch_count_di) - 1; | |
353 | devc->curr_di = have; | |
354 | } | |
355 | ||
356 | return SR_OK; | |
357 | } | |
358 | ||
359 | /* Query the state of an individual relay channel. */ | |
360 | SR_PRIV int devantech_eth008_query_do(const struct sr_dev_inst *sdi, | |
361 | const struct sr_channel_group *cg, gboolean *on) | |
362 | { | |
363 | struct dev_context *devc; | |
364 | struct channel_group_context *cgc; | |
365 | uint32_t have; | |
366 | int ret; | |
367 | ||
368 | devc = sdi->priv; | |
369 | if (!devc) | |
370 | return SR_ERR_ARG; | |
371 | ||
372 | /* Unconditionally update the internal cache. */ | |
373 | ret = devantech_eth008_cache_state(sdi); | |
374 | if (ret != SR_OK) | |
375 | return ret; | |
376 | ||
377 | /* | |
378 | * Only reject unexpected requeusts after the update. Get the | |
379 | * individual channel's state from the cache of all channels. | |
380 | */ | |
381 | if (!cg) | |
382 | return SR_ERR_ARG; | |
383 | cgc = cg->priv; | |
384 | if (!cgc) | |
385 | return SR_ERR_BUG; | |
386 | if (cgc->index >= devc->model->ch_count_do) | |
387 | return SR_ERR_ARG; | |
388 | have = devc->curr_do; | |
389 | have >>= cgc->index; | |
390 | have &= 1 << 0; | |
391 | if (on) | |
392 | *on = have ? TRUE : FALSE; | |
393 | ||
394 | return SR_OK; | |
395 | } | |
396 | ||
397 | /* | |
398 | * Manipulate the state of an individual relay channel (when cg is given). | |
399 | * Or set/clear all channels at the same time (when cg is NULL). | |
400 | */ | |
401 | SR_PRIV int devantech_eth008_setup_do(const struct sr_dev_inst *sdi, | |
402 | const struct sr_channel_group *cg, gboolean on) | |
403 | { | |
404 | struct sr_serial_dev_inst *serial; | |
405 | struct dev_context *devc; | |
406 | size_t width_do; | |
407 | struct channel_group_context *cgc; | |
408 | size_t number; | |
409 | uint32_t reg; | |
410 | uint8_t req[4], *wrptr, cmd; | |
411 | uint8_t rsp[1], v8; | |
412 | const uint8_t *rdptr; | |
413 | int ret; | |
414 | ||
415 | serial = sdi->conn; | |
416 | if (!serial) | |
417 | return SR_ERR_ARG; | |
418 | devc = sdi->priv; | |
419 | if (!devc) | |
420 | return SR_ERR_ARG; | |
421 | cgc = cg ? cg->priv : NULL; | |
422 | if (cgc && cgc->index >= devc->model->ch_count_do) | |
423 | return SR_ERR_ARG; | |
424 | ||
425 | width_do = devc->model->width_do; | |
426 | if (1 + width_do > sizeof(req)) | |
427 | return SR_ERR_NA; | |
428 | ||
429 | wrptr = req; | |
430 | if (cgc) { | |
431 | /* Manipulate an individual channel. */ | |
432 | cmd = on ? CMD_DIGITAL_ACTIVE : CMD_DIGITAL_INACTIVE; | |
433 | number = cgc->number; | |
434 | write_u8_inc(&wrptr, cmd); | |
435 | write_u8_inc(&wrptr, number & 0xff); | |
436 | write_u8_inc(&wrptr, 0); /* Just set/clear, no pulse. */ | |
437 | } else { | |
438 | /* Manipulate all channels at the same time. */ | |
439 | reg = on ? devc->mask_do : 0; | |
440 | write_u8_inc(&wrptr, CMD_DIGITAL_SET_OUTPUTS); | |
441 | switch (width_do) { | |
442 | case 1: | |
443 | write_u8_inc(&wrptr, reg & 0xff); | |
444 | break; | |
445 | case 2: | |
446 | write_u16le_inc(&wrptr, reg & 0xffff); | |
447 | break; | |
448 | case 3: | |
449 | write_u24le_inc(&wrptr, reg & 0xffffff); | |
450 | break; | |
451 | default: | |
452 | return SR_ERR_NA; | |
453 | } | |
454 | } | |
455 | ret = send_then_recv(serial, req, wrptr - req, rsp, sizeof(rsp)); | |
456 | if (ret != SR_OK) | |
457 | return ret; | |
458 | rdptr = rsp; | |
459 | ||
460 | v8 = read_u8_inc(&rdptr); | |
461 | if (v8 != 0) | |
462 | return SR_ERR_DATA; | |
463 | ||
464 | return SR_OK; | |
465 | } | |
466 | ||
467 | SR_PRIV int devantech_eth008_query_di(const struct sr_dev_inst *sdi, | |
468 | const struct sr_channel_group *cg, gboolean *on) | |
469 | { | |
470 | struct dev_context *devc; | |
471 | struct channel_group_context *cgc; | |
472 | uint32_t have; | |
473 | int ret; | |
474 | ||
475 | /* Unconditionally update the internal cache. */ | |
476 | ret = devantech_eth008_cache_state(sdi); | |
477 | if (ret != SR_OK) | |
478 | return ret; | |
479 | ||
480 | /* | |
481 | * Only reject unexpected requeusts after the update. Get the | |
482 | * individual channel's state from the cache of all channels. | |
483 | */ | |
484 | devc = sdi->priv; | |
485 | if (!devc) | |
486 | return SR_ERR_ARG; | |
487 | if (!cg) | |
488 | return SR_ERR_ARG; | |
489 | cgc = cg->priv; | |
490 | if (!cgc) | |
491 | return SR_ERR_BUG; | |
492 | if (cgc->index >= devc->model->ch_count_di) | |
493 | return SR_ERR_ARG; | |
494 | have = devc->curr_di; | |
495 | have >>= cgc->index; | |
496 | have &= 1 << 0; | |
497 | if (on) | |
498 | *on = have ? TRUE : FALSE; | |
499 | ||
500 | return SR_OK; | |
501 | } | |
502 | ||
503 | SR_PRIV int devantech_eth008_query_ai(const struct sr_dev_inst *sdi, | |
504 | const struct sr_channel_group *cg, uint16_t *adc_value) | |
505 | { | |
506 | struct sr_serial_dev_inst *serial; | |
507 | struct dev_context *devc; | |
508 | struct channel_group_context *cgc; | |
509 | uint8_t req[2], *wrptr; | |
510 | uint8_t rsp[2]; | |
511 | const uint8_t *rdptr; | |
512 | uint32_t have; | |
513 | int ret; | |
514 | ||
515 | serial = sdi->conn; | |
516 | if (!serial) | |
517 | return SR_ERR_ARG; | |
518 | devc = sdi->priv; | |
519 | if (!devc) | |
520 | return SR_ERR_ARG; | |
521 | if (!cg) | |
522 | return SR_ERR_ARG; | |
523 | cgc = cg->priv; | |
524 | if (!cgc) | |
525 | return SR_ERR_ARG; | |
526 | if (cgc->index >= devc->model->ch_count_ai) | |
527 | return SR_ERR_ARG; | |
528 | ||
529 | wrptr = req; | |
530 | write_u8_inc(&wrptr, CMD_ANALOG_GET_INPUT); | |
531 | write_u8_inc(&wrptr, cgc->number & 0xff); | |
532 | ret = send_then_recv(serial, req, wrptr - req, rsp, sizeof(rsp)); | |
533 | if (ret != SR_OK) | |
534 | return ret; | |
535 | rdptr = rsp; | |
536 | ||
537 | /* | |
538 | * TODO The u16 BE format is a guess. Needs verification. | |
539 | * As is the unit-less nature of that value. | |
540 | */ | |
541 | have = read_u16be_inc(&rdptr); | |
542 | if (adc_value) | |
543 | *adc_value = have; | |
544 | ||
545 | return SR_OK; | |
546 | } | |
547 | ||
548 | SR_PRIV int devantech_eth008_query_supply(const struct sr_dev_inst *sdi, | |
549 | const struct sr_channel_group *cg, uint16_t *millivolts) | |
550 | { | |
551 | struct sr_serial_dev_inst *serial; | |
552 | uint8_t req[1], *wrptr; | |
553 | uint8_t rsp[1]; | |
554 | const uint8_t *rdptr; | |
555 | uint16_t have; | |
556 | int ret; | |
557 | ||
558 | (void)cg; | |
559 | ||
560 | serial = sdi->conn; | |
561 | if (!serial) | |
562 | return SR_ERR_ARG; | |
563 | ||
564 | wrptr = req; | |
565 | write_u8_inc(&wrptr, CMD_GET_SUPPLY_VOLTS); | |
566 | ret = send_then_recv(serial, req, wrptr - req, rsp, sizeof(rsp)); | |
567 | if (ret != SR_OK) | |
568 | return ret; | |
569 | rdptr = rsp; | |
570 | ||
571 | /* Gets a byte for voltage in units of 0.1V. Scale up to mV. */ | |
572 | have = read_u8_inc(&rdptr); | |
573 | have *= 100; | |
574 | if (millivolts) | |
575 | *millivolts = have; | |
576 | ||
577 | return SR_OK; | |
578 | } |