1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * HX711: analog to digital converter for weight sensor module 4 * 5 * Copyright (c) 2016 Andreas Klinger <ak@it-klinger.de> 6 */ 7 #include <linux/err.h> 8 #include <linux/kernel.h> 9 #include <linux/module.h> 10 #include <linux/of.h> 11 #include <linux/platform_device.h> 12 #include <linux/property.h> 13 #include <linux/slab.h> 14 #include <linux/sched.h> 15 #include <linux/delay.h> 16 #include <linux/iio/iio.h> 17 #include <linux/iio/sysfs.h> 18 #include <linux/iio/buffer.h> 19 #include <linux/iio/trigger_consumer.h> 20 #include <linux/iio/triggered_buffer.h> 21 #include <linux/gpio/consumer.h> 22 #include <linux/regulator/consumer.h> 23 24 /* gain to pulse and scale conversion */ 25 #define HX711_GAIN_MAX 3 26 27 struct hx711_gain_to_scale { 28 int gain; 29 int gain_pulse; 30 int scale; 31 int channel; 32 }; 33 34 /* 35 * .scale depends on AVDD which in turn is known as soon as the regulator 36 * is available 37 * therefore we set .scale in hx711_probe() 38 * 39 * channel A in documentation is channel 0 in source code 40 * channel B in documentation is channel 1 in source code 41 */ 42 static struct hx711_gain_to_scale hx711_gain_to_scale[HX711_GAIN_MAX] = { 43 { 128, 1, 0, 0 }, 44 { 32, 2, 0, 1 }, 45 { 64, 3, 0, 0 } 46 }; 47 48 static int hx711_get_gain_to_pulse(int gain) 49 { 50 int i; 51 52 for (i = 0; i < HX711_GAIN_MAX; i++) 53 if (hx711_gain_to_scale[i].gain == gain) 54 return hx711_gain_to_scale[i].gain_pulse; 55 return 1; 56 } 57 58 static int hx711_get_gain_to_scale(int gain) 59 { 60 int i; 61 62 for (i = 0; i < HX711_GAIN_MAX; i++) 63 if (hx711_gain_to_scale[i].gain == gain) 64 return hx711_gain_to_scale[i].scale; 65 return 0; 66 } 67 68 static int hx711_get_scale_to_gain(int scale) 69 { 70 int i; 71 72 for (i = 0; i < HX711_GAIN_MAX; i++) 73 if (hx711_gain_to_scale[i].scale == scale) 74 return hx711_gain_to_scale[i].gain; 75 return -EINVAL; 76 } 77 78 struct hx711_data { 79 struct device *dev; 80 struct gpio_desc *gpiod_pd_sck; 81 struct gpio_desc *gpiod_dout; 82 struct regulator *reg_avdd; 83 int gain_set; /* gain set on device */ 84 int gain_chan_a; /* gain for channel A */ 85 struct mutex lock; 86 /* 87 * triggered buffer 88 * 2x32-bit channel + 64-bit timestamp 89 */ 90 u32 buffer[4]; 91 /* 92 * delay after a rising edge on SCK until the data is ready DOUT 93 * this is dependent on the hx711 where the datasheet tells a 94 * maximum value of 100 ns 95 * but also on potential parasitic capacities on the wiring 96 */ 97 u32 data_ready_delay_ns; 98 u32 clock_frequency; 99 }; 100 101 static int hx711_cycle(struct hx711_data *hx711_data) 102 { 103 int val; 104 105 /* 106 * if preempted for more then 60us while PD_SCK is high: 107 * hx711 is going in reset 108 * ==> measuring is false 109 */ 110 preempt_disable(); 111 gpiod_set_value(hx711_data->gpiod_pd_sck, 1); 112 113 /* 114 * wait until DOUT is ready 115 * it turned out that parasitic capacities are extending the time 116 * until DOUT has reached it's value 117 */ 118 ndelay(hx711_data->data_ready_delay_ns); 119 120 val = gpiod_get_value(hx711_data->gpiod_dout); 121 /* 122 * here we are not waiting for 0.2 us as suggested by the datasheet, 123 * because the oscilloscope showed in a test scenario 124 * at least 1.15 us for PD_SCK high (T3 in datasheet) 125 * and 0.56 us for PD_SCK low on TI Sitara with 800 MHz 126 */ 127 gpiod_set_value(hx711_data->gpiod_pd_sck, 0); 128 preempt_enable(); 129 130 /* 131 * make it a square wave for addressing cases with capacitance on 132 * PC_SCK 133 */ 134 ndelay(hx711_data->data_ready_delay_ns); 135 136 return val; 137 } 138 139 static int hx711_read(struct hx711_data *hx711_data) 140 { 141 int i, ret; 142 int value = 0; 143 int val = gpiod_get_value(hx711_data->gpiod_dout); 144 145 /* we double check if it's really down */ 146 if (val) 147 return -EIO; 148 149 for (i = 0; i < 24; i++) { 150 value <<= 1; 151 ret = hx711_cycle(hx711_data); 152 if (ret) 153 value++; 154 } 155 156 value ^= 0x800000; 157 158 for (i = 0; i < hx711_get_gain_to_pulse(hx711_data->gain_set); i++) 159 hx711_cycle(hx711_data); 160 161 return value; 162 } 163 164 static int hx711_wait_for_ready(struct hx711_data *hx711_data) 165 { 166 int i, val; 167 168 /* 169 * in some rare cases the reset takes quite a long time 170 * especially when the channel is changed. 171 * Allow up to one second for it 172 */ 173 for (i = 0; i < 100; i++) { 174 val = gpiod_get_value(hx711_data->gpiod_dout); 175 if (!val) 176 break; 177 /* sleep at least 10 ms */ 178 msleep(10); 179 } 180 if (val) 181 return -EIO; 182 183 return 0; 184 } 185 186 static int hx711_reset(struct hx711_data *hx711_data) 187 { 188 int ret; 189 int val = gpiod_get_value(hx711_data->gpiod_dout); 190 191 if (val) { 192 /* 193 * an examination with the oszilloscope indicated 194 * that the first value read after the reset is not stable 195 * if we reset too short; 196 * the shorter the reset cycle 197 * the less reliable the first value after reset is; 198 * there were no problems encountered with a value 199 * of 10 ms or higher 200 */ 201 gpiod_set_value(hx711_data->gpiod_pd_sck, 1); 202 msleep(10); 203 gpiod_set_value(hx711_data->gpiod_pd_sck, 0); 204 205 ret = hx711_wait_for_ready(hx711_data); 206 if (ret) 207 return ret; 208 /* 209 * after a reset the gain is 128 so we do a dummy read 210 * to set the gain for the next read 211 */ 212 ret = hx711_read(hx711_data); 213 if (ret < 0) 214 return ret; 215 216 /* 217 * after a dummy read we need to wait vor readiness 218 * for not mixing gain pulses with the clock 219 */ 220 val = hx711_wait_for_ready(hx711_data); 221 } 222 223 return val; 224 } 225 226 static int hx711_set_gain_for_channel(struct hx711_data *hx711_data, int chan) 227 { 228 int ret; 229 230 if (chan == 0) { 231 if (hx711_data->gain_set == 32) { 232 hx711_data->gain_set = hx711_data->gain_chan_a; 233 234 ret = hx711_read(hx711_data); 235 if (ret < 0) 236 return ret; 237 238 ret = hx711_wait_for_ready(hx711_data); 239 if (ret) 240 return ret; 241 } 242 } else { 243 if (hx711_data->gain_set != 32) { 244 hx711_data->gain_set = 32; 245 246 ret = hx711_read(hx711_data); 247 if (ret < 0) 248 return ret; 249 250 ret = hx711_wait_for_ready(hx711_data); 251 if (ret) 252 return ret; 253 } 254 } 255 256 return 0; 257 } 258 259 static int hx711_reset_read(struct hx711_data *hx711_data, int chan) 260 { 261 int ret; 262 int val; 263 264 /* 265 * hx711_reset() must be called from here 266 * because it could be calling hx711_read() by itself 267 */ 268 if (hx711_reset(hx711_data)) { 269 dev_err(hx711_data->dev, "reset failed!"); 270 return -EIO; 271 } 272 273 ret = hx711_set_gain_for_channel(hx711_data, chan); 274 if (ret < 0) 275 return ret; 276 277 val = hx711_read(hx711_data); 278 279 return val; 280 } 281 282 static int hx711_read_raw(struct iio_dev *indio_dev, 283 const struct iio_chan_spec *chan, 284 int *val, int *val2, long mask) 285 { 286 struct hx711_data *hx711_data = iio_priv(indio_dev); 287 288 switch (mask) { 289 case IIO_CHAN_INFO_RAW: 290 mutex_lock(&hx711_data->lock); 291 292 *val = hx711_reset_read(hx711_data, chan->channel); 293 294 mutex_unlock(&hx711_data->lock); 295 296 if (*val < 0) 297 return *val; 298 return IIO_VAL_INT; 299 case IIO_CHAN_INFO_SCALE: 300 *val = 0; 301 mutex_lock(&hx711_data->lock); 302 303 *val2 = hx711_get_gain_to_scale(hx711_data->gain_set); 304 305 mutex_unlock(&hx711_data->lock); 306 307 return IIO_VAL_INT_PLUS_NANO; 308 default: 309 return -EINVAL; 310 } 311 } 312 313 static int hx711_write_raw(struct iio_dev *indio_dev, 314 struct iio_chan_spec const *chan, 315 int val, 316 int val2, 317 long mask) 318 { 319 struct hx711_data *hx711_data = iio_priv(indio_dev); 320 int ret; 321 int gain; 322 323 switch (mask) { 324 case IIO_CHAN_INFO_SCALE: 325 /* 326 * a scale greater than 1 mV per LSB is not possible 327 * with the HX711, therefore val must be 0 328 */ 329 if (val != 0) 330 return -EINVAL; 331 332 mutex_lock(&hx711_data->lock); 333 334 gain = hx711_get_scale_to_gain(val2); 335 if (gain < 0) { 336 mutex_unlock(&hx711_data->lock); 337 return gain; 338 } 339 340 if (gain != hx711_data->gain_set) { 341 hx711_data->gain_set = gain; 342 if (gain != 32) 343 hx711_data->gain_chan_a = gain; 344 345 ret = hx711_read(hx711_data); 346 if (ret < 0) { 347 mutex_unlock(&hx711_data->lock); 348 return ret; 349 } 350 } 351 352 mutex_unlock(&hx711_data->lock); 353 return 0; 354 default: 355 return -EINVAL; 356 } 357 358 return 0; 359 } 360 361 static int hx711_write_raw_get_fmt(struct iio_dev *indio_dev, 362 struct iio_chan_spec const *chan, 363 long mask) 364 { 365 return IIO_VAL_INT_PLUS_NANO; 366 } 367 368 static irqreturn_t hx711_trigger(int irq, void *p) 369 { 370 struct iio_poll_func *pf = p; 371 struct iio_dev *indio_dev = pf->indio_dev; 372 struct hx711_data *hx711_data = iio_priv(indio_dev); 373 int i, j = 0; 374 375 mutex_lock(&hx711_data->lock); 376 377 memset(hx711_data->buffer, 0, sizeof(hx711_data->buffer)); 378 379 for (i = 0; i < indio_dev->masklength; i++) { 380 if (!test_bit(i, indio_dev->active_scan_mask)) 381 continue; 382 383 hx711_data->buffer[j] = hx711_reset_read(hx711_data, 384 indio_dev->channels[i].channel); 385 j++; 386 } 387 388 iio_push_to_buffers_with_timestamp(indio_dev, hx711_data->buffer, 389 pf->timestamp); 390 391 mutex_unlock(&hx711_data->lock); 392 393 iio_trigger_notify_done(indio_dev->trig); 394 395 return IRQ_HANDLED; 396 } 397 398 static ssize_t hx711_scale_available_show(struct device *dev, 399 struct device_attribute *attr, 400 char *buf) 401 { 402 struct iio_dev_attr *iio_attr = to_iio_dev_attr(attr); 403 int channel = iio_attr->address; 404 int i, len = 0; 405 406 for (i = 0; i < HX711_GAIN_MAX; i++) 407 if (hx711_gain_to_scale[i].channel == channel) 408 len += sprintf(buf + len, "0.%09d ", 409 hx711_gain_to_scale[i].scale); 410 411 len += sprintf(buf + len, "\n"); 412 413 return len; 414 } 415 416 static IIO_DEVICE_ATTR(in_voltage0_scale_available, S_IRUGO, 417 hx711_scale_available_show, NULL, 0); 418 419 static IIO_DEVICE_ATTR(in_voltage1_scale_available, S_IRUGO, 420 hx711_scale_available_show, NULL, 1); 421 422 static struct attribute *hx711_attributes[] = { 423 &iio_dev_attr_in_voltage0_scale_available.dev_attr.attr, 424 &iio_dev_attr_in_voltage1_scale_available.dev_attr.attr, 425 NULL, 426 }; 427 428 static const struct attribute_group hx711_attribute_group = { 429 .attrs = hx711_attributes, 430 }; 431 432 static const struct iio_info hx711_iio_info = { 433 .read_raw = hx711_read_raw, 434 .write_raw = hx711_write_raw, 435 .write_raw_get_fmt = hx711_write_raw_get_fmt, 436 .attrs = &hx711_attribute_group, 437 }; 438 439 static const struct iio_chan_spec hx711_chan_spec[] = { 440 { 441 .type = IIO_VOLTAGE, 442 .channel = 0, 443 .indexed = 1, 444 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), 445 .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), 446 .scan_index = 0, 447 .scan_type = { 448 .sign = 'u', 449 .realbits = 24, 450 .storagebits = 32, 451 .endianness = IIO_CPU, 452 }, 453 }, 454 { 455 .type = IIO_VOLTAGE, 456 .channel = 1, 457 .indexed = 1, 458 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), 459 .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), 460 .scan_index = 1, 461 .scan_type = { 462 .sign = 'u', 463 .realbits = 24, 464 .storagebits = 32, 465 .endianness = IIO_CPU, 466 }, 467 }, 468 IIO_CHAN_SOFT_TIMESTAMP(2), 469 }; 470 471 static int hx711_probe(struct platform_device *pdev) 472 { 473 struct device *dev = &pdev->dev; 474 struct device_node *np = dev->of_node; 475 struct hx711_data *hx711_data; 476 struct iio_dev *indio_dev; 477 int ret; 478 int i; 479 480 indio_dev = devm_iio_device_alloc(dev, sizeof(struct hx711_data)); 481 if (!indio_dev) { 482 dev_err(dev, "failed to allocate IIO device\n"); 483 return -ENOMEM; 484 } 485 486 hx711_data = iio_priv(indio_dev); 487 hx711_data->dev = dev; 488 489 mutex_init(&hx711_data->lock); 490 491 /* 492 * PD_SCK stands for power down and serial clock input of HX711 493 * in the driver it is an output 494 */ 495 hx711_data->gpiod_pd_sck = devm_gpiod_get(dev, "sck", GPIOD_OUT_LOW); 496 if (IS_ERR(hx711_data->gpiod_pd_sck)) { 497 dev_err(dev, "failed to get sck-gpiod: err=%ld\n", 498 PTR_ERR(hx711_data->gpiod_pd_sck)); 499 return PTR_ERR(hx711_data->gpiod_pd_sck); 500 } 501 502 /* 503 * DOUT stands for serial data output of HX711 504 * for the driver it is an input 505 */ 506 hx711_data->gpiod_dout = devm_gpiod_get(dev, "dout", GPIOD_IN); 507 if (IS_ERR(hx711_data->gpiod_dout)) { 508 dev_err(dev, "failed to get dout-gpiod: err=%ld\n", 509 PTR_ERR(hx711_data->gpiod_dout)); 510 return PTR_ERR(hx711_data->gpiod_dout); 511 } 512 513 hx711_data->reg_avdd = devm_regulator_get(dev, "avdd"); 514 if (IS_ERR(hx711_data->reg_avdd)) 515 return PTR_ERR(hx711_data->reg_avdd); 516 517 ret = regulator_enable(hx711_data->reg_avdd); 518 if (ret < 0) 519 return ret; 520 521 /* 522 * with 523 * full scale differential input range: AVDD / GAIN 524 * full scale output data: 2^24 525 * we can say: 526 * AVDD / GAIN = 2^24 527 * therefore: 528 * 1 LSB = AVDD / GAIN / 2^24 529 * AVDD is in uV, but we need 10^-9 mV 530 * approximately to fit into a 32 bit number: 531 * 1 LSB = (AVDD * 100) / GAIN / 1678 [10^-9 mV] 532 */ 533 ret = regulator_get_voltage(hx711_data->reg_avdd); 534 if (ret < 0) 535 goto error_regulator; 536 537 /* we need 10^-9 mV */ 538 ret *= 100; 539 540 for (i = 0; i < HX711_GAIN_MAX; i++) 541 hx711_gain_to_scale[i].scale = 542 ret / hx711_gain_to_scale[i].gain / 1678; 543 544 hx711_data->gain_set = 128; 545 hx711_data->gain_chan_a = 128; 546 547 hx711_data->clock_frequency = 400000; 548 ret = of_property_read_u32(np, "clock-frequency", 549 &hx711_data->clock_frequency); 550 551 /* 552 * datasheet says the high level of PD_SCK has a maximum duration 553 * of 50 microseconds 554 */ 555 if (hx711_data->clock_frequency < 20000) { 556 dev_warn(dev, "clock-frequency too low - assuming 400 kHz\n"); 557 hx711_data->clock_frequency = 400000; 558 } 559 560 hx711_data->data_ready_delay_ns = 561 1000000000 / hx711_data->clock_frequency; 562 563 platform_set_drvdata(pdev, indio_dev); 564 565 indio_dev->name = "hx711"; 566 indio_dev->dev.parent = &pdev->dev; 567 indio_dev->info = &hx711_iio_info; 568 indio_dev->modes = INDIO_DIRECT_MODE; 569 indio_dev->channels = hx711_chan_spec; 570 indio_dev->num_channels = ARRAY_SIZE(hx711_chan_spec); 571 572 ret = iio_triggered_buffer_setup(indio_dev, iio_pollfunc_store_time, 573 hx711_trigger, NULL); 574 if (ret < 0) { 575 dev_err(dev, "setup of iio triggered buffer failed\n"); 576 goto error_regulator; 577 } 578 579 ret = iio_device_register(indio_dev); 580 if (ret < 0) { 581 dev_err(dev, "Couldn't register the device\n"); 582 goto error_buffer; 583 } 584 585 return 0; 586 587 error_buffer: 588 iio_triggered_buffer_cleanup(indio_dev); 589 590 error_regulator: 591 regulator_disable(hx711_data->reg_avdd); 592 593 return ret; 594 } 595 596 static int hx711_remove(struct platform_device *pdev) 597 { 598 struct hx711_data *hx711_data; 599 struct iio_dev *indio_dev; 600 601 indio_dev = platform_get_drvdata(pdev); 602 hx711_data = iio_priv(indio_dev); 603 604 iio_device_unregister(indio_dev); 605 606 iio_triggered_buffer_cleanup(indio_dev); 607 608 regulator_disable(hx711_data->reg_avdd); 609 610 return 0; 611 } 612 613 static const struct of_device_id of_hx711_match[] = { 614 { .compatible = "avia,hx711", }, 615 {}, 616 }; 617 618 MODULE_DEVICE_TABLE(of, of_hx711_match); 619 620 static struct platform_driver hx711_driver = { 621 .probe = hx711_probe, 622 .remove = hx711_remove, 623 .driver = { 624 .name = "hx711-gpio", 625 .of_match_table = of_hx711_match, 626 }, 627 }; 628 629 module_platform_driver(hx711_driver); 630 631 MODULE_AUTHOR("Andreas Klinger <ak@it-klinger.de>"); 632 MODULE_DESCRIPTION("HX711 bitbanging driver - ADC for weight cells"); 633 MODULE_LICENSE("GPL"); 634 MODULE_ALIAS("platform:hx711-gpio"); 635 636