src/hardware/fluke-dmm/fluke.c

   1 /*
   2  * This file is part of the libsigrok project.
   3  *
   4  * Copyright (C) 2012 Bert Vermeulen <bert@biot.com>
   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 #include <config.h>
  21 #include <stdlib.h>
  22 #include <math.h>
  23 #include <string.h>
  24 #include <glib.h>
  25 #include <libsigrok/libsigrok.h>
  26 #include "libsigrok-internal.h"
  27 #include "fluke-dmm.h"
  28
  29 static struct sr_datafeed_analog *handle_qm_18x(const struct sr_dev_inst *sdi,
  30                 char **tokens)
  31 {
  32         struct sr_datafeed_analog *analog;
  33         struct sr_analog_encoding encoding;
  34         struct sr_analog_meaning meaning;
  35         struct sr_analog_spec spec;
  36         float fvalue;
  37         char *e, *u;
  38         gboolean is_oor;
  39
  40         if (strcmp(tokens[0], "QM") || !tokens[1])
  41                 return NULL;
  42
  43         if ((e = strstr(tokens[1], "Out of range"))) {
  44                 is_oor = TRUE;
  45                 fvalue = -1;
  46                 while (*e && *e != '.')
  47                         e++;
  48         } else {
  49                 is_oor = FALSE;
  50                 /* Delimit the float, since sr_atof_ascii() wants only
  51                  * a valid float here. */
  52                 e = tokens[1];
  53                 while (*e && *e != ' ')
  54                         e++;
  55                 *e++ = '\0';
  56                 if (sr_atof_ascii(tokens[1], &fvalue) != SR_OK || fvalue == 0.0) {
  57                         /* Happens all the time, when switching modes. */
  58                         sr_dbg("Invalid float.");
  59                         return NULL;
  60                 }
  61         }
  62         while (*e && *e == ' ')
  63                 e++;
  64
  65         analog = g_malloc0(sizeof(struct sr_datafeed_analog));
  66         sr_analog_init(analog, &encoding, &meaning, &spec, 0);
  67         analog->data = g_malloc(sizeof(float));
  68         analog->meaning->channels = sdi->channels;
  69         analog->num_samples = 1;
  70         if (is_oor)
  71                 *((float *)analog->data) = NAN;
  72         else
  73                 *((float *)analog->data) = fvalue;
  74         analog->meaning->mq = 0;
  75
  76         if ((u = strstr(e, "V DC")) || (u = strstr(e, "V AC"))) {
  77                 analog->meaning->mq = SR_MQ_VOLTAGE;
  78                 analog->meaning->unit = SR_UNIT_VOLT;
  79                 if (!is_oor && e[0] == 'm')
  80                         *((float *)analog->data) /= 1000;
  81                 /* This catches "V AC", "V DC" and "V AC+DC". */
  82                 if (strstr(u, "AC"))
  83                         analog->meaning->mqflags |= SR_MQFLAG_AC | SR_MQFLAG_RMS;
  84                 if (strstr(u, "DC"))
  85                         analog->meaning->mqflags |= SR_MQFLAG_DC;
  86         } else if ((u = strstr(e, "dBV")) || (u = strstr(e, "dBm"))) {
  87                 analog->meaning->mq = SR_MQ_VOLTAGE;
  88                 if (u[2] == 'm')
  89                         analog->meaning->unit = SR_UNIT_DECIBEL_MW;
  90                 else
  91                         analog->meaning->unit = SR_UNIT_DECIBEL_VOLT;
  92                 analog->meaning->mqflags |= SR_MQFLAG_AC | SR_MQFLAG_RMS;
  93         } else if ((u = strstr(e, "Ohms"))) {
  94                 analog->meaning->mq = SR_MQ_RESISTANCE;
  95                 analog->meaning->unit = SR_UNIT_OHM;
  96                 if (is_oor)
  97                         *((float *)analog->data) = INFINITY;
  98                 else if (e[0] == 'k')
  99                         *((float *)analog->data) *= 1000;
 100                 else if (e[0] == 'M')
 101                         *((float *)analog->data) *= 1000000;
 102         } else if (!strcmp(e, "nS")) {
 103                 analog->meaning->mq = SR_MQ_CONDUCTANCE;
 104                 analog->meaning->unit = SR_UNIT_SIEMENS;
 105                 *((float *)analog->data) /= 1e+9;
 106         } else if ((u = strstr(e, "Farads"))) {
 107                 analog->meaning->mq = SR_MQ_CAPACITANCE;
 108                 analog->meaning->unit = SR_UNIT_FARAD;
 109                 if (!is_oor) {
 110                         if (e[0] == 'm')
 111                                 *((float *)analog->data) /= 1e+3;
 112                         else if (e[0] == 'u')
 113                                 *((float *)analog->data) /= 1e+6;
 114                         else if (e[0] == 'n')
 115                                 *((float *)analog->data) /= 1e+9;
 116                 }
 117         } else if ((u = strstr(e, "Deg C")) || (u = strstr(e, "Deg F"))) {
 118                 analog->meaning->mq = SR_MQ_TEMPERATURE;
 119                 if (u[4] == 'C')
 120                         analog->meaning->unit = SR_UNIT_CELSIUS;
 121                 else
 122                         analog->meaning->unit = SR_UNIT_FAHRENHEIT;
 123         } else if ((u = strstr(e, "A AC")) || (u = strstr(e, "A DC"))) {
 124                 analog->meaning->mq = SR_MQ_CURRENT;
 125                 analog->meaning->unit = SR_UNIT_AMPERE;
 126                 /* This catches "A AC", "A DC" and "A AC+DC". */
 127                 if (strstr(u, "AC"))
 128                         analog->meaning->mqflags |= SR_MQFLAG_AC | SR_MQFLAG_RMS;
 129                 if (strstr(u, "DC"))
 130                         analog->meaning->mqflags |= SR_MQFLAG_DC;
 131                 if (!is_oor) {
 132                         if (e[0] == 'm')
 133                                 *((float *)analog->data) /= 1e+3;
 134                         else if (e[0] == 'u')
 135                                 *((float *)analog->data) /= 1e+6;
 136                 }
 137         } else if ((u = strstr(e, "Hz"))) {
 138                 analog->meaning->mq = SR_MQ_FREQUENCY;
 139                 analog->meaning->unit = SR_UNIT_HERTZ;
 140                 if (e[0] == 'k')
 141                         *((float *)analog->data) *= 1e+3;
 142         } else if (!strcmp(e, "%")) {
 143                 analog->meaning->mq = SR_MQ_DUTY_CYCLE;
 144                 analog->meaning->unit = SR_UNIT_PERCENTAGE;
 145         } else if ((u = strstr(e, "ms"))) {
 146                 analog->meaning->mq = SR_MQ_PULSE_WIDTH;
 147                 analog->meaning->unit = SR_UNIT_SECOND;
 148                 *((float *)analog->data) /= 1e+3;
 149         }
 150
 151         if (analog->meaning->mq == 0) {
 152                 /* Not a valid measurement. */
 153                 g_free(analog->data);
 154                 g_free(analog);
 155                 analog = NULL;
 156         }
 157
 158         return analog;
 159 }
 160
 161 static struct sr_datafeed_analog *handle_qm_28x(const struct sr_dev_inst *sdi,
 162                 char **tokens)
 163 {
 164         struct sr_datafeed_analog *analog;
 165         struct sr_analog_encoding encoding;
 166         struct sr_analog_meaning meaning;
 167         struct sr_analog_spec spec;
 168         float fvalue;
 169
 170         if (!tokens[1])
 171                 return NULL;
 172
 173         if (sr_atof_ascii(tokens[0], &fvalue) != SR_OK || fvalue == 0.0) {
 174                 sr_err("Invalid float '%s'.", tokens[0]);
 175                 return NULL;
 176         }
 177
 178         analog = g_malloc0(sizeof(struct sr_datafeed_analog));
 179         sr_analog_init(analog, &encoding, &meaning, &spec, 0);
 180         analog->data = g_malloc(sizeof(float));
 181         analog->meaning->channels = sdi->channels;
 182         analog->num_samples = 1;
 183         *((float *)analog->data) = fvalue;
 184         analog->meaning->mq = 0;
 185
 186         if (!strcmp(tokens[1], "VAC") || !strcmp(tokens[1], "VDC")) {
 187                 analog->meaning->mq = SR_MQ_VOLTAGE;
 188                 analog->meaning->unit = SR_UNIT_VOLT;
 189                 if (!strcmp(tokens[2], "NORMAL")) {
 190                         if (tokens[1][1] == 'A') {
 191                                 analog->meaning->mqflags |= SR_MQFLAG_AC;
 192                                 analog->meaning->mqflags |= SR_MQFLAG_RMS;
 193                         } else
 194                                 analog->meaning->mqflags |= SR_MQFLAG_DC;
 195                 } else if (!strcmp(tokens[2], "OL") || !strcmp(tokens[2], "OL_MINUS")) {
 196                         *((float *)analog->data) = NAN;
 197                 } else
 198                         analog->meaning->mq = 0;
 199         } else if (!strcmp(tokens[1], "dBV") || !strcmp(tokens[1], "dBm")) {
 200                 analog->meaning->mq = SR_MQ_VOLTAGE;
 201                 if (tokens[1][2] == 'm')
 202                         analog->meaning->unit = SR_UNIT_DECIBEL_MW;
 203                 else
 204                         analog->meaning->unit = SR_UNIT_DECIBEL_VOLT;
 205                 analog->meaning->mqflags |= SR_MQFLAG_AC | SR_MQFLAG_RMS;
 206         } else if (!strcmp(tokens[1], "CEL") || !strcmp(tokens[1], "FAR")) {
 207                 if (!strcmp(tokens[2], "NORMAL")) {
 208                         analog->meaning->mq = SR_MQ_TEMPERATURE;
 209                         if (tokens[1][0] == 'C')
 210                                 analog->meaning->unit = SR_UNIT_CELSIUS;
 211                         else
 212                                 analog->meaning->unit = SR_UNIT_FAHRENHEIT;
 213                 }
 214         } else if (!strcmp(tokens[1], "OHM")) {
 215                 if (!strcmp(tokens[3], "NONE")) {
 216                         analog->meaning->mq = SR_MQ_RESISTANCE;
 217                         analog->meaning->unit = SR_UNIT_OHM;
 218                         if (!strcmp(tokens[2], "OL") || !strcmp(tokens[2], "OL_MINUS")) {
 219                                 *((float *)analog->data) = INFINITY;
 220                         } else if (strcmp(tokens[2], "NORMAL"))
 221                                 analog->meaning->mq = 0;
 222                 } else if (!strcmp(tokens[3], "OPEN_CIRCUIT")) {
 223                         analog->meaning->mq = SR_MQ_CONTINUITY;
 224                         analog->meaning->unit = SR_UNIT_BOOLEAN;
 225                         *((float *)analog->data) = 0.0;
 226                 } else if (!strcmp(tokens[3], "SHORT_CIRCUIT")) {
 227                         analog->meaning->mq = SR_MQ_CONTINUITY;
 228                         analog->meaning->unit = SR_UNIT_BOOLEAN;
 229                         *((float *)analog->data) = 1.0;
 230                 }
 231         } else if (!strcmp(tokens[1], "F")
 232                         && !strcmp(tokens[2], "NORMAL")
 233                         && !strcmp(tokens[3], "NONE")) {
 234                 analog->meaning->mq = SR_MQ_CAPACITANCE;
 235                 analog->meaning->unit = SR_UNIT_FARAD;
 236         } else if (!strcmp(tokens[1], "AAC") || !strcmp(tokens[1], "ADC")) {
 237                 analog->meaning->mq = SR_MQ_CURRENT;
 238                 analog->meaning->unit = SR_UNIT_AMPERE;
 239                 if (!strcmp(tokens[2], "NORMAL")) {
 240                         if (tokens[1][1] == 'A') {
 241                                 analog->meaning->mqflags |= SR_MQFLAG_AC;
 242                                 analog->meaning->mqflags |= SR_MQFLAG_RMS;
 243                         } else
 244                                 analog->meaning->mqflags |= SR_MQFLAG_DC;
 245                 } else if (!strcmp(tokens[2], "OL") || !strcmp(tokens[2], "OL_MINUS")) {
 246                         *((float *)analog->data) = NAN;
 247                 } else
 248                         analog->meaning->mq = 0;
 249         } if (!strcmp(tokens[1], "Hz") && !strcmp(tokens[2], "NORMAL")) {
 250                 analog->meaning->mq = SR_MQ_FREQUENCY;
 251                 analog->meaning->unit = SR_UNIT_HERTZ;
 252         } else if (!strcmp(tokens[1], "PCT") && !strcmp(tokens[2], "NORMAL")) {
 253                 analog->meaning->mq = SR_MQ_DUTY_CYCLE;
 254                 analog->meaning->unit = SR_UNIT_PERCENTAGE;
 255         } else if (!strcmp(tokens[1], "S") && !strcmp(tokens[2], "NORMAL")) {
 256                 analog->meaning->mq = SR_MQ_PULSE_WIDTH;
 257                 analog->meaning->unit = SR_UNIT_SECOND;
 258         } else if (!strcmp(tokens[1], "SIE") && !strcmp(tokens[2], "NORMAL")) {
 259                 analog->meaning->mq = SR_MQ_CONDUCTANCE;
 260                 analog->meaning->unit = SR_UNIT_SIEMENS;
 261         }
 262
 263         if (analog->meaning->mq == 0) {
 264                 /* Not a valid measurement. */
 265                 g_free(analog->data);
 266                 g_free(analog);
 267                 analog = NULL;
 268         }
 269
 270         return analog;
 271 }
 272
 273 static void handle_qm_19x_meta(const struct sr_dev_inst *sdi, char **tokens)
 274 {
 275         struct dev_context *devc;
 276         int meas_type, meas_unit, meas_char, i;
 277
 278         /* Make sure we have 7 valid tokens. */
 279         for (i = 0; tokens[i] && i < 7; i++);
 280         if (i != 7)
 281                 return;
 282
 283         if (strcmp(tokens[1], "1"))
 284                 /* Invalid measurement. */
 285                 return;
 286
 287         if (strcmp(tokens[2], "3"))
 288                 /* Only interested in input from the meter mode source. */
 289                 return;
 290
 291         devc = sdi->priv;
 292
 293         /* Measurement type 11 == absolute, 19 = relative */
 294         meas_type = strtol(tokens[0], NULL, 10);
 295         if (meas_type != 11 && meas_type != 19)
 296                 /* Device is in some mode we don't support. */
 297                 return;
 298
 299         /* We might get metadata for absolute and relative mode (if the device
 300          * is in relative mode). In that case, relative takes precedence. */
 301         if (meas_type == 11 && devc->meas_type == 19)
 302                 return;
 303
 304         meas_unit = strtol(tokens[3], NULL, 10);
 305         if (meas_unit == 0)
 306                 /* Device is turned off. Really. */
 307                 return;
 308         meas_char = strtol(tokens[4], NULL, 10);
 309
 310         devc->mq = devc->unit = devc->mqflags = 0;
 311         switch (meas_unit) {
 312         case 1:
 313                 devc->mq = SR_MQ_VOLTAGE;
 314                 devc->unit = SR_UNIT_VOLT;
 315                 if (meas_char == 1)
 316                         devc->mqflags |= SR_MQFLAG_DC;
 317                 else if (meas_char == 2)
 318                         devc->mqflags |= SR_MQFLAG_AC;
 319                 else if (meas_char == 3)
 320                         devc->mqflags |= SR_MQFLAG_DC | SR_MQFLAG_AC;
 321                 else if (meas_char == 15)
 322                         devc->mqflags |= SR_MQFLAG_DIODE;
 323                 break;
 324         case 2:
 325                 devc->mq = SR_MQ_CURRENT;
 326                 devc->unit = SR_UNIT_AMPERE;
 327                 if (meas_char == 1)
 328                         devc->mqflags |= SR_MQFLAG_DC;
 329                 else if (meas_char == 2)
 330                         devc->mqflags |= SR_MQFLAG_AC;
 331                 else if (meas_char == 3)
 332                         devc->mqflags |= SR_MQFLAG_DC | SR_MQFLAG_AC;
 333                 break;
 334         case 3:
 335                 if (meas_char == 1) {
 336                         devc->mq = SR_MQ_RESISTANCE;
 337                         devc->unit = SR_UNIT_OHM;
 338                 } else if (meas_char == 16) {
 339                         devc->mq = SR_MQ_CONTINUITY;
 340                         devc->unit = SR_UNIT_BOOLEAN;
 341                 }
 342                 break;
 343         case 12:
 344                 devc->mq = SR_MQ_TEMPERATURE;
 345                 devc->unit = SR_UNIT_CELSIUS;
 346                 break;
 347         case 13:
 348                 devc->mq = SR_MQ_TEMPERATURE;
 349                 devc->unit = SR_UNIT_FAHRENHEIT;
 350                 break;
 351         default:
 352                 sr_dbg("unknown unit: %d", meas_unit);
 353         }
 354         if (devc->mq == 0 && devc->unit == 0)
 355                 return;
 356
 357         /* If we got here, we know how to interpret the measurement. */
 358         devc->meas_type = meas_type;
 359         if (meas_type == 11)
 360                 /* Absolute meter reading. */
 361                 devc->is_relative = FALSE;
 362         else if (!strcmp(tokens[0], "19"))
 363                 /* Relative meter reading. */
 364                 devc->is_relative = TRUE;
 365
 366 }
 367
 368 static void handle_qm_19x_data(const struct sr_dev_inst *sdi, char **tokens)
 369 {
 370         struct dev_context *devc;
 371         struct sr_datafeed_packet packet;
 372         struct sr_datafeed_analog analog;
 373         struct sr_analog_encoding encoding;
 374         struct sr_analog_meaning meaning;
 375         struct sr_analog_spec spec;
 376         float fvalue;
 377
 378         if (!strcmp(tokens[0], "9.9E+37")) {
 379                 /* An invalid measurement shows up on the display as "OL", but
 380                  * comes through like this. Since comparing 38-digit floats
 381                  * is rather problematic, we'll cut through this here. */
 382                 fvalue = NAN;
 383         } else {
 384                 if (sr_atof_ascii(tokens[0], &fvalue) != SR_OK || fvalue == 0.0) {
 385                         sr_err("Invalid float '%s'.", tokens[0]);
 386                         return;
 387                 }
 388         }
 389
 390         devc = sdi->priv;
 391         if (devc->mq == 0 || devc->unit == 0)
 392                 /* Don't have valid metadata yet. */
 393                 return;
 394
 395         if (devc->mq == SR_MQ_RESISTANCE && isnan(fvalue))
 396                 fvalue = INFINITY;
 397         else if (devc->mq == SR_MQ_CONTINUITY) {
 398                 if (isnan(fvalue))
 399                         fvalue = 0.0;
 400                 else
 401                         fvalue = 1.0;
 402         }
 403
 404         sr_analog_init(&analog, &encoding, &meaning, &spec, 0);
 405         analog.meaning->channels = sdi->channels;
 406         analog.num_samples = 1;
 407         analog.data = &fvalue;
 408         analog.meaning->mq = devc->mq;
 409         analog.meaning->unit = devc->unit;
 410         analog.meaning->mqflags = 0;
 411         packet.type = SR_DF_ANALOG;
 412         packet.payload = &analog;
 413         sr_session_send(sdi, &packet);
 414
 415         sr_sw_limits_update_samples_read(&devc->limits, 1);
 416 }
 417
 418 static void handle_line(const struct sr_dev_inst *sdi)
 419 {
 420         struct dev_context *devc;
 421         struct sr_serial_dev_inst *serial;
 422         struct sr_datafeed_packet packet;
 423         struct sr_datafeed_analog *analog;
 424         int num_tokens, n, i;
 425         char cmd[16], **tokens;
 426
 427         devc = sdi->priv;
 428         serial = sdi->conn;
 429         sr_spew("Received line '%s' (%d).", devc->buf, devc->buflen);
 430
 431         if (devc->buflen == 1) {
 432                 if (devc->buf[0] != '0') {
 433                         /* Not just a CMD_ACK from the query command. */
 434                         sr_dbg("Got CMD_ACK '%c'.", devc->buf[0]);
 435                         devc->expect_response = FALSE;
 436                 }
 437                 devc->buflen = 0;
 438                 return;
 439         }
 440
 441         analog = NULL;
 442         tokens = g_strsplit(devc->buf, ",", 0);
 443         if (tokens[0]) {
 444                 if (devc->profile->model == FLUKE_187 || devc->profile->model == FLUKE_189) {
 445                         devc->expect_response = FALSE;
 446                         analog = handle_qm_18x(sdi, tokens);
 447                 } else if (devc->profile->model == FLUKE_287 || devc->profile->model == FLUKE_289) {
 448                         devc->expect_response = FALSE;
 449                         analog = handle_qm_28x(sdi, tokens);
 450                 } else if (devc->profile->model == FLUKE_190) {
 451                         devc->expect_response = FALSE;
 452                         for (num_tokens = 0; tokens[num_tokens]; num_tokens++);
 453                         if (num_tokens >= 7) {
 454                                 /* Response to QM: this is a comma-separated list of
 455                                  * fields with metadata about the measurement. This
 456                                  * format can return multiple sets of metadata,
 457                                  * split into sets of 7 tokens each. */
 458                                 devc->meas_type = 0;
 459                                 for (i = 0; i < num_tokens; i += 7)
 460                                         handle_qm_19x_meta(sdi, tokens + i);
 461                                 if (devc->meas_type) {
 462                                         /* Slip the request in now, before the main
 463                                          * timer loop asks for metadata again. */
 464                                         n = sprintf(cmd, "QM %d\r", devc->meas_type);
 465                                         if (serial_write_blocking(serial, cmd, n, SERIAL_WRITE_TIMEOUT_MS) < 0)
 466                                                 sr_err("Unable to send QM (measurement).");
 467                                 }
 468                         } else {
 469                                 /* Response to QM <n> measurement request. */
 470                                 handle_qm_19x_data(sdi, tokens);
 471                         }
 472                 }
 473         }
 474         g_strfreev(tokens);
 475         devc->buflen = 0;
 476
 477         if (analog) {
 478                 /* Got a measurement. */
 479                 packet.type = SR_DF_ANALOG;
 480                 packet.payload = analog;
 481                 sr_session_send(sdi, &packet);
 482                 sr_sw_limits_update_samples_read(&devc->limits, 1);
 483                 g_free(analog->data);
 484                 g_free(analog);
 485         }
 486
 487 }
 488
 489 SR_PRIV int fluke_receive_data(int fd, int revents, void *cb_data)
 490 {
 491         struct sr_dev_inst *sdi;
 492         struct dev_context *devc;
 493         struct sr_serial_dev_inst *serial;
 494         int len;
 495         int64_t now, elapsed;
 496
 497         (void)fd;
 498
 499         if (!(sdi = cb_data))
 500                 return TRUE;
 501
 502         if (!(devc = sdi->priv))
 503                 return TRUE;
 504
 505         serial = sdi->conn;
 506         if (revents == G_IO_IN) {
 507                 /* Serial data arrived. */
 508                 while (FLUKEDMM_BUFSIZE - devc->buflen - 1 > 0) {
 509                         len = serial_read_nonblocking(serial, devc->buf + devc->buflen, 1);
 510                         if (len < 1)
 511                                 break;
 512                         devc->buflen++;
 513                         *(devc->buf + devc->buflen) = '\0';
 514                         if (*(devc->buf + devc->buflen - 1) == '\r') {
 515                                 *(devc->buf + --devc->buflen) = '\0';
 516                                 handle_line(sdi);
 517                                 break;
 518                         }
 519                 }
 520         }
 521
 522         if (sr_sw_limits_check(&devc->limits)) {
 523                 sdi->driver->dev_acquisition_stop(sdi);
 524                 return TRUE;
 525         }
 526
 527         now = g_get_monotonic_time() / 1000;
 528         elapsed = now - devc->cmd_sent_at;
 529         /* Send query command at poll_period interval, or after 1 second
 530          * has elapsed. This will make it easier to recover from any
 531          * out-of-sync or temporary disconnect issues. */
 532         if ((devc->expect_response == FALSE && elapsed > devc->profile->poll_period)
 533                         || elapsed > devc->profile->timeout) {
 534                 if (serial_write_blocking(serial, "QM\r", 3, SERIAL_WRITE_TIMEOUT_MS) < 0)
 535                         sr_err("Unable to send QM.");
 536                 devc->cmd_sent_at = now;
 537                 devc->expect_response = TRUE;
 538         }
 539
 540         return TRUE;
 541 }