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 #define HX711_RESET_GAIN 128 27 28 struct hx711_gain_to_scale { 29 int gain; 30 int gain_pulse; 31 int scale; 32 int channel; 33 }; 34 35 /* 36 * .scale depends on AVDD which in turn is known as soon as the regulator 37 * is available 38 * therefore we set .scale in hx711_probe() 39 * 40 * channel A in documentation is channel 0 in source code 41 * channel B in documentation is channel 1 in source code 42 */ 43 static struct hx711_gain_to_scale hx711_gain_to_scale[HX711_GAIN_MAX] = { 44 { 128, 1, 0, 0 }, 45 { 32, 2, 0, 1 }, 46 { 64, 3, 0, 0 } 47 }; 48 49 static int hx711_get_gain_to_pulse(int gain) 50 { 51 int i; 52 53 for (i = 0; i < HX711_GAIN_MAX; i++) 54 if (hx711_gain_to_scale[i].gain == gain) 55 return hx711_gain_to_scale[i].gain_pulse; 56 return 1; 57 } 58 59 static int hx711_get_gain_to_scale(int gain) 60 { 61 int i; 62 63 for (i = 0; i < HX711_GAIN_MAX; i++) 64 if (hx711_gain_to_scale[i].gain == gain) 65 return hx711_gain_to_scale[i].scale; 66 return 0; 67 } 68 69 static int hx711_get_scale_to_gain(int scale) 70 { 71 int i; 72 73 for (i = 0; i < HX711_GAIN_MAX; i++) 74 if (hx711_gain_to_scale[i].scale == scale) 75 return hx711_gain_to_scale[i].gain; 76 return -EINVAL; 77 } 78 79 struct hx711_data { 80 struct device *dev; 81 struct gpio_desc *gpiod_pd_sck; 82 struct gpio_desc *gpiod_dout; 83 struct regulator *reg_avdd; 84 int gain_set; /* gain set on device */ 85 int gain_chan_a; /* gain for channel A */ 86 struct mutex lock; 87 /* 88 * triggered buffer 89 * 2x32-bit channel + 64-bit naturally aligned timestamp 90 */ 91 u32 buffer[4] __aligned(8); 92 /* 93 * delay after a rising edge on SCK until the data is ready DOUT 94 * this is dependent on the hx711 where the datasheet tells a 95 * maximum value of 100 ns 96 * but also on potential parasitic capacities on the wiring 97 */ 98 u32 data_ready_delay_ns; 99 u32 clock_frequency; 100 }; 101 102 static int hx711_cycle(struct hx711_data *hx711_data) 103 { 104 unsigned long flags; 105 106 /* 107 * if preempted for more then 60us while PD_SCK is high: 108 * hx711 is going in reset 109 * ==> measuring is false 110 */ 111 local_irq_save(flags); 112 gpiod_set_value(hx711_data->gpiod_pd_sck, 1); 113 114 /* 115 * wait until DOUT is ready 116 * it turned out that parasitic capacities are extending the time 117 * until DOUT has reached it's value 118 */ 119 ndelay(hx711_data->data_ready_delay_ns); 120 121 /* 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 local_irq_restore(flags); 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 /* sample as late as possible */ 137 return gpiod_get_value(hx711_data->gpiod_dout); 138 } 139 140 static int hx711_read(struct hx711_data *hx711_data) 141 { 142 int i, ret; 143 int value = 0; 144 int val = gpiod_get_value(hx711_data->gpiod_dout); 145 146 /* we double check if it's really down */ 147 if (val) 148 return -EIO; 149 150 for (i = 0; i < 24; i++) { 151 value <<= 1; 152 ret = hx711_cycle(hx711_data); 153 if (ret) 154 value++; 155 } 156 157 value ^= 0x800000; 158 159 for (i = 0; i < hx711_get_gain_to_pulse(hx711_data->gain_set); i++) 160 hx711_cycle(hx711_data); 161 162 return value; 163 } 164 165 static int hx711_wait_for_ready(struct hx711_data *hx711_data) 166 { 167 int i, val; 168 169 /* 170 * in some rare cases the reset takes quite a long time 171 * especially when the channel is changed. 172 * Allow up to one second for it 173 */ 174 for (i = 0; i < 100; i++) { 175 val = gpiod_get_value(hx711_data->gpiod_dout); 176 if (!val) 177 break; 178 /* sleep at least 10 ms */ 179 msleep(10); 180 } 181 if (val) 182 return -EIO; 183 184 return 0; 185 } 186 187 static int hx711_reset(struct hx711_data *hx711_data) 188 { 189 int val = hx711_wait_for_ready(hx711_data); 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 val = hx711_wait_for_ready(hx711_data); 206 207 /* after a reset the gain is 128 */ 208 hx711_data->gain_set = HX711_RESET_GAIN; 209 } 210 211 return val; 212 } 213 214 static int hx711_set_gain_for_channel(struct hx711_data *hx711_data, int chan) 215 { 216 int ret; 217 218 if (chan == 0) { 219 if (hx711_data->gain_set == 32) { 220 hx711_data->gain_set = hx711_data->gain_chan_a; 221 222 ret = hx711_read(hx711_data); 223 if (ret < 0) 224 return ret; 225 226 ret = hx711_wait_for_ready(hx711_data); 227 if (ret) 228 return ret; 229 } 230 } else { 231 if (hx711_data->gain_set != 32) { 232 hx711_data->gain_set = 32; 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 } 243 244 return 0; 245 } 246 247 static int hx711_reset_read(struct hx711_data *hx711_data, int chan) 248 { 249 int ret; 250 int val; 251 252 /* 253 * hx711_reset() must be called from here 254 * because it could be calling hx711_read() by itself 255 */ 256 if (hx711_reset(hx711_data)) { 257 dev_err(hx711_data->dev, "reset failed!"); 258 return -EIO; 259 } 260 261 ret = hx711_set_gain_for_channel(hx711_data, chan); 262 if (ret < 0) 263 return ret; 264 265 val = hx711_read(hx711_data); 266 267 return val; 268 } 269 270 static int hx711_read_raw(struct iio_dev *indio_dev, 271 const struct iio_chan_spec *chan, 272 int *val, int *val2, long mask) 273 { 274 struct hx711_data *hx711_data = iio_priv(indio_dev); 275 276 switch (mask) { 277 case IIO_CHAN_INFO_RAW: 278 mutex_lock(&hx711_data->lock); 279 280 *val = hx711_reset_read(hx711_data, chan->channel); 281 282 mutex_unlock(&hx711_data->lock); 283 284 if (*val < 0) 285 return *val; 286 return IIO_VAL_INT; 287 case IIO_CHAN_INFO_SCALE: 288 *val = 0; 289 mutex_lock(&hx711_data->lock); 290 291 *val2 = hx711_get_gain_to_scale(hx711_data->gain_set); 292 293 mutex_unlock(&hx711_data->lock); 294 295 return IIO_VAL_INT_PLUS_NANO; 296 default: 297 return -EINVAL; 298 } 299 } 300 301 static int hx711_write_raw(struct iio_dev *indio_dev, 302 struct iio_chan_spec const *chan, 303 int val, 304 int val2, 305 long mask) 306 { 307 struct hx711_data *hx711_data = iio_priv(indio_dev); 308 int ret; 309 int gain; 310 311 switch (mask) { 312 case IIO_CHAN_INFO_SCALE: 313 /* 314 * a scale greater than 1 mV per LSB is not possible 315 * with the HX711, therefore val must be 0 316 */ 317 if (val != 0) 318 return -EINVAL; 319 320 mutex_lock(&hx711_data->lock); 321 322 gain = hx711_get_scale_to_gain(val2); 323 if (gain < 0) { 324 mutex_unlock(&hx711_data->lock); 325 return gain; 326 } 327 328 if (gain != hx711_data->gain_set) { 329 hx711_data->gain_set = gain; 330 if (gain != 32) 331 hx711_data->gain_chan_a = gain; 332 333 ret = hx711_read(hx711_data); 334 if (ret < 0) { 335 mutex_unlock(&hx711_data->lock); 336 return ret; 337 } 338 } 339 340 mutex_unlock(&hx711_data->lock); 341 return 0; 342 default: 343 return -EINVAL; 344 } 345 346 return 0; 347 } 348 349 static int hx711_write_raw_get_fmt(struct iio_dev *indio_dev, 350 struct iio_chan_spec const *chan, 351 long mask) 352 { 353 return IIO_VAL_INT_PLUS_NANO; 354 } 355 356 static irqreturn_t hx711_trigger(int irq, void *p) 357 { 358 struct iio_poll_func *pf = p; 359 struct iio_dev *indio_dev = pf->indio_dev; 360 struct hx711_data *hx711_data = iio_priv(indio_dev); 361 int i, j = 0; 362 363 mutex_lock(&hx711_data->lock); 364 365 memset(hx711_data->buffer, 0, sizeof(hx711_data->buffer)); 366 367 for (i = 0; i < indio_dev->masklength; i++) { 368 if (!test_bit(i, indio_dev->active_scan_mask)) 369 continue; 370 371 hx711_data->buffer[j] = hx711_reset_read(hx711_data, 372 indio_dev->channels[i].channel); 373 j++; 374 } 375 376 iio_push_to_buffers_with_timestamp(indio_dev, hx711_data->buffer, 377 pf->timestamp); 378 379 mutex_unlock(&hx711_data->lock); 380 381 iio_trigger_notify_done(indio_dev->trig); 382 383 return IRQ_HANDLED; 384 } 385 386 static ssize_t hx711_scale_available_show(struct device *dev, 387 struct device_attribute *attr, 388 char *buf) 389 { 390 struct iio_dev_attr *iio_attr = to_iio_dev_attr(attr); 391 int channel = iio_attr->address; 392 int i, len = 0; 393 394 for (i = 0; i < HX711_GAIN_MAX; i++) 395 if (hx711_gain_to_scale[i].channel == channel) 396 len += sprintf(buf + len, "0.%09d ", 397 hx711_gain_to_scale[i].scale); 398 399 len += sprintf(buf + len, "\n"); 400 401 return len; 402 } 403 404 static IIO_DEVICE_ATTR(in_voltage0_scale_available, S_IRUGO, 405 hx711_scale_available_show, NULL, 0); 406 407 static IIO_DEVICE_ATTR(in_voltage1_scale_available, S_IRUGO, 408 hx711_scale_available_show, NULL, 1); 409 410 static struct attribute *hx711_attributes[] = { 411 &iio_dev_attr_in_voltage0_scale_available.dev_attr.attr, 412 &iio_dev_attr_in_voltage1_scale_available.dev_attr.attr, 413 NULL, 414 }; 415 416 static const struct attribute_group hx711_attribute_group = { 417 .attrs = hx711_attributes, 418 }; 419 420 static const struct iio_info hx711_iio_info = { 421 .read_raw = hx711_read_raw, 422 .write_raw = hx711_write_raw, 423 .write_raw_get_fmt = hx711_write_raw_get_fmt, 424 .attrs = &hx711_attribute_group, 425 }; 426 427 static const struct iio_chan_spec hx711_chan_spec[] = { 428 { 429 .type = IIO_VOLTAGE, 430 .channel = 0, 431 .indexed = 1, 432 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), 433 .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), 434 .scan_index = 0, 435 .scan_type = { 436 .sign = 'u', 437 .realbits = 24, 438 .storagebits = 32, 439 .endianness = IIO_CPU, 440 }, 441 }, 442 { 443 .type = IIO_VOLTAGE, 444 .channel = 1, 445 .indexed = 1, 446 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), 447 .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), 448 .scan_index = 1, 449 .scan_type = { 450 .sign = 'u', 451 .realbits = 24, 452 .storagebits = 32, 453 .endianness = IIO_CPU, 454 }, 455 }, 456 IIO_CHAN_SOFT_TIMESTAMP(2), 457 }; 458 459 static int hx711_probe(struct platform_device *pdev) 460 { 461 struct device *dev = &pdev->dev; 462 struct device_node *np = dev->of_node; 463 struct hx711_data *hx711_data; 464 struct iio_dev *indio_dev; 465 int ret; 466 int i; 467 468 indio_dev = devm_iio_device_alloc(dev, sizeof(struct hx711_data)); 469 if (!indio_dev) { 470 dev_err(dev, "failed to allocate IIO device\n"); 471 return -ENOMEM; 472 } 473 474 hx711_data = iio_priv(indio_dev); 475 hx711_data->dev = dev; 476 477 mutex_init(&hx711_data->lock); 478 479 /* 480 * PD_SCK stands for power down and serial clock input of HX711 481 * in the driver it is an output 482 */ 483 hx711_data->gpiod_pd_sck = devm_gpiod_get(dev, "sck", GPIOD_OUT_LOW); 484 if (IS_ERR(hx711_data->gpiod_pd_sck)) { 485 dev_err(dev, "failed to get sck-gpiod: err=%ld\n", 486 PTR_ERR(hx711_data->gpiod_pd_sck)); 487 return PTR_ERR(hx711_data->gpiod_pd_sck); 488 } 489 490 /* 491 * DOUT stands for serial data output of HX711 492 * for the driver it is an input 493 */ 494 hx711_data->gpiod_dout = devm_gpiod_get(dev, "dout", GPIOD_IN); 495 if (IS_ERR(hx711_data->gpiod_dout)) { 496 dev_err(dev, "failed to get dout-gpiod: err=%ld\n", 497 PTR_ERR(hx711_data->gpiod_dout)); 498 return PTR_ERR(hx711_data->gpiod_dout); 499 } 500 501 hx711_data->reg_avdd = devm_regulator_get(dev, "avdd"); 502 if (IS_ERR(hx711_data->reg_avdd)) 503 return PTR_ERR(hx711_data->reg_avdd); 504 505 ret = regulator_enable(hx711_data->reg_avdd); 506 if (ret < 0) 507 return ret; 508 509 /* 510 * with 511 * full scale differential input range: AVDD / GAIN 512 * full scale output data: 2^24 513 * we can say: 514 * AVDD / GAIN = 2^24 515 * therefore: 516 * 1 LSB = AVDD / GAIN / 2^24 517 * AVDD is in uV, but we need 10^-9 mV 518 * approximately to fit into a 32 bit number: 519 * 1 LSB = (AVDD * 100) / GAIN / 1678 [10^-9 mV] 520 */ 521 ret = regulator_get_voltage(hx711_data->reg_avdd); 522 if (ret < 0) 523 goto error_regulator; 524 525 /* we need 10^-9 mV */ 526 ret *= 100; 527 528 for (i = 0; i < HX711_GAIN_MAX; i++) 529 hx711_gain_to_scale[i].scale = 530 ret / hx711_gain_to_scale[i].gain / 1678; 531 532 hx711_data->gain_set = 128; 533 hx711_data->gain_chan_a = 128; 534 535 hx711_data->clock_frequency = 400000; 536 ret = of_property_read_u32(np, "clock-frequency", 537 &hx711_data->clock_frequency); 538 539 /* 540 * datasheet says the high level of PD_SCK has a maximum duration 541 * of 50 microseconds 542 */ 543 if (hx711_data->clock_frequency < 20000) { 544 dev_warn(dev, "clock-frequency too low - assuming 400 kHz\n"); 545 hx711_data->clock_frequency = 400000; 546 } 547 548 hx711_data->data_ready_delay_ns = 549 1000000000 / hx711_data->clock_frequency; 550 551 platform_set_drvdata(pdev, indio_dev); 552 553 indio_dev->name = "hx711"; 554 indio_dev->info = &hx711_iio_info; 555 indio_dev->modes = INDIO_DIRECT_MODE; 556 indio_dev->channels = hx711_chan_spec; 557 indio_dev->num_channels = ARRAY_SIZE(hx711_chan_spec); 558 559 ret = iio_triggered_buffer_setup(indio_dev, iio_pollfunc_store_time, 560 hx711_trigger, NULL); 561 if (ret < 0) { 562 dev_err(dev, "setup of iio triggered buffer failed\n"); 563 goto error_regulator; 564 } 565 566 ret = iio_device_register(indio_dev); 567 if (ret < 0) { 568 dev_err(dev, "Couldn't register the device\n"); 569 goto error_buffer; 570 } 571 572 return 0; 573 574 error_buffer: 575 iio_triggered_buffer_cleanup(indio_dev); 576 577 error_regulator: 578 regulator_disable(hx711_data->reg_avdd); 579 580 return ret; 581 } 582 583 static int hx711_remove(struct platform_device *pdev) 584 { 585 struct hx711_data *hx711_data; 586 struct iio_dev *indio_dev; 587 588 indio_dev = platform_get_drvdata(pdev); 589 hx711_data = iio_priv(indio_dev); 590 591 iio_device_unregister(indio_dev); 592 593 iio_triggered_buffer_cleanup(indio_dev); 594 595 regulator_disable(hx711_data->reg_avdd); 596 597 return 0; 598 } 599 600 static const struct of_device_id of_hx711_match[] = { 601 { .compatible = "avia,hx711", }, 602 {}, 603 }; 604 605 MODULE_DEVICE_TABLE(of, of_hx711_match); 606 607 static struct platform_driver hx711_driver = { 608 .probe = hx711_probe, 609 .remove = hx711_remove, 610 .driver = { 611 .name = "hx711-gpio", 612 .of_match_table = of_hx711_match, 613 }, 614 }; 615 616 module_platform_driver(hx711_driver); 617 618 MODULE_AUTHOR("Andreas Klinger <ak@it-klinger.de>"); 619 MODULE_DESCRIPTION("HX711 bitbanging driver - ADC for weight cells"); 620 MODULE_LICENSE("GPL"); 621 MODULE_ALIAS("platform:hx711-gpio"); 622 623