1 // SPDX-License-Identifier: GPL-2.0
3 * Sensirion SCD4X carbon dioxide sensor i2c driver
5 * Copyright (C) 2021 Protonic Holland
6 * Author: Roan van Dijk <roan@protonic.nl>
8 * I2C slave address: 0x62
11 * https://www.sensirion.com/file/datasheet_scd4x
14 #include <asm/unaligned.h>
15 #include <linux/crc8.h>
16 #include <linux/delay.h>
17 #include <linux/device.h>
18 #include <linux/i2c.h>
19 #include <linux/iio/buffer.h>
20 #include <linux/iio/iio.h>
21 #include <linux/iio/sysfs.h>
22 #include <linux/iio/trigger.h>
23 #include <linux/iio/trigger_consumer.h>
24 #include <linux/iio/triggered_buffer.h>
25 #include <linux/iio/types.h>
26 #include <linux/kernel.h>
27 #include <linux/mutex.h>
28 #include <linux/string.h>
29 #include <linux/sysfs.h>
30 #include <linux/types.h>
32 #define SCD4X_CRC8_POLYNOMIAL 0x31
33 #define SCD4X_TIMEOUT_ERR 1000
34 #define SCD4X_READ_BUF_SIZE 9
35 #define SCD4X_COMMAND_BUF_SIZE 2
36 #define SCD4X_WRITE_BUF_SIZE 5
37 #define SCD4X_FRC_MIN_PPM 0
38 #define SCD4X_FRC_MAX_PPM 2000
39 #define SCD4X_PRESSURE_COMP_MIN_MBAR 700
40 #define SCD4X_PRESSURE_COMP_MAX_MBAR 1200
41 #define SCD4X_READY_MASK 0x01
45 CMD_START_MEAS = 0x21b1,
46 CMD_READ_MEAS = 0xec05,
47 CMD_STOP_MEAS = 0x3f86,
48 CMD_SET_TEMP_OFFSET = 0x241d,
49 CMD_GET_TEMP_OFFSET = 0x2318,
50 CMD_SET_AMB_PRESSURE = 0xe000,
51 CMD_GET_AMB_PRESSURE = 0xe000,
55 CMD_GET_DATA_READY = 0xe4b8,
58 enum scd4x_channel_idx {
65 struct i2c_client *client;
66 /* maintain access to device, to prevent concurrent reads/writes */
68 struct regulator *vdd;
71 DECLARE_CRC8_TABLE(scd4x_crc8_table);
73 static int scd4x_i2c_xfer(struct scd4x_state *state, char *txbuf, int txsize,
74 char *rxbuf, int rxsize)
76 struct i2c_client *client = state->client;
79 ret = i2c_master_send(client, txbuf, txsize);
89 ret = i2c_master_recv(client, rxbuf, rxsize);
98 static int scd4x_send_command(struct scd4x_state *state, enum scd4x_cmd cmd)
100 char buf[SCD4X_COMMAND_BUF_SIZE];
104 * Measurement needs to be stopped before sending commands.
105 * Except stop and start command.
107 if ((cmd != CMD_STOP_MEAS) && (cmd != CMD_START_MEAS)) {
109 ret = scd4x_send_command(state, CMD_STOP_MEAS);
113 /* execution time for stopping measurement */
114 msleep_interruptible(500);
117 put_unaligned_be16(cmd, buf);
118 ret = scd4x_i2c_xfer(state, buf, 2, buf, 0);
122 if ((cmd != CMD_STOP_MEAS) && (cmd != CMD_START_MEAS)) {
123 ret = scd4x_send_command(state, CMD_START_MEAS);
131 static int scd4x_read(struct scd4x_state *state, enum scd4x_cmd cmd,
132 void *response, int response_sz)
134 struct i2c_client *client = state->client;
135 char buf[SCD4X_READ_BUF_SIZE];
136 char *rsp = response;
141 * Measurement needs to be stopped before sending commands.
142 * Except for reading measurement and data ready command.
144 if ((cmd != CMD_GET_DATA_READY) && (cmd != CMD_READ_MEAS) &&
145 (cmd != CMD_GET_AMB_PRESSURE)) {
146 ret = scd4x_send_command(state, CMD_STOP_MEAS);
150 /* execution time for stopping measurement */
151 msleep_interruptible(500);
154 /* CRC byte for every 2 bytes of data */
155 response_sz += response_sz / 2;
157 put_unaligned_be16(cmd, buf);
158 ret = scd4x_i2c_xfer(state, buf, 2, buf, response_sz);
162 for (i = 0; i < response_sz; i += 3) {
163 crc = crc8(scd4x_crc8_table, buf + i, 2, CRC8_INIT_VALUE);
164 if (crc != buf[i + 2]) {
165 dev_err(&client->dev, "CRC error\n");
173 /* start measurement */
174 if ((cmd != CMD_GET_DATA_READY) && (cmd != CMD_READ_MEAS) &&
175 (cmd != CMD_GET_AMB_PRESSURE)) {
176 ret = scd4x_send_command(state, CMD_START_MEAS);
184 static int scd4x_write(struct scd4x_state *state, enum scd4x_cmd cmd, uint16_t arg)
186 char buf[SCD4X_WRITE_BUF_SIZE];
190 put_unaligned_be16(cmd, buf);
191 put_unaligned_be16(arg, buf + 2);
193 crc = crc8(scd4x_crc8_table, buf + 2, 2, CRC8_INIT_VALUE);
196 /* measurement needs to be stopped before sending commands */
197 if (cmd != CMD_SET_AMB_PRESSURE) {
198 ret = scd4x_send_command(state, CMD_STOP_MEAS);
204 msleep_interruptible(500);
206 ret = scd4x_i2c_xfer(state, buf, SCD4X_WRITE_BUF_SIZE, buf, 0);
210 /* start measurement, except for forced calibration command */
211 if ((cmd != CMD_FRC) && (cmd != CMD_SET_AMB_PRESSURE)) {
212 ret = scd4x_send_command(state, CMD_START_MEAS);
220 static int scd4x_write_and_fetch(struct scd4x_state *state, enum scd4x_cmd cmd,
221 uint16_t arg, void *response, int response_sz)
223 struct i2c_client *client = state->client;
224 char buf[SCD4X_READ_BUF_SIZE];
225 char *rsp = response;
229 ret = scd4x_write(state, CMD_FRC, arg);
234 msleep_interruptible(400);
236 /* CRC byte for every 2 bytes of data */
237 response_sz += response_sz / 2;
239 ret = i2c_master_recv(client, buf, response_sz);
242 if (ret != response_sz) {
247 for (i = 0; i < response_sz; i += 3) {
248 crc = crc8(scd4x_crc8_table, buf + i, 2, CRC8_INIT_VALUE);
249 if (crc != buf[i + 2]) {
250 dev_err(&client->dev, "CRC error\n");
259 return scd4x_send_command(state, CMD_START_MEAS);
263 * on error try to start the measurement,
264 * puts sensor back into continuous measurement
266 scd4x_send_command(state, CMD_START_MEAS);
271 static int scd4x_read_meas(struct scd4x_state *state, uint16_t *meas)
276 ret = scd4x_read(state, CMD_READ_MEAS, buf, sizeof(buf));
280 for (i = 0; i < ARRAY_SIZE(buf); i++)
281 meas[i] = be16_to_cpu(buf[i]);
286 static int scd4x_wait_meas_poll(struct scd4x_state *state)
288 struct i2c_client *client = state->client;
296 ret = scd4x_read(state, CMD_GET_DATA_READY, &bval, sizeof(bval));
299 val = be16_to_cpu(bval);
301 /* new measurement available */
305 msleep_interruptible(1000);
308 /* try to start sensor on timeout */
309 ret = scd4x_send_command(state, CMD_START_MEAS);
311 dev_err(&client->dev, "failed to start measurement: %d\n", ret);
316 static int scd4x_read_poll(struct scd4x_state *state, uint16_t *buf)
320 ret = scd4x_wait_meas_poll(state);
324 return scd4x_read_meas(state, buf);
327 static int scd4x_read_channel(struct scd4x_state *state, int chan)
332 ret = scd4x_read_poll(state, buf);
339 static int scd4x_read_raw(struct iio_dev *indio_dev,
340 struct iio_chan_spec const *chan, int *val,
341 int *val2, long mask)
343 struct scd4x_state *state = iio_priv(indio_dev);
348 case IIO_CHAN_INFO_RAW:
350 mutex_lock(&state->lock);
351 ret = scd4x_read(state, CMD_GET_AMB_PRESSURE, &tmp, sizeof(tmp));
352 mutex_unlock(&state->lock);
357 *val = be16_to_cpu(tmp);
361 ret = iio_device_claim_direct_mode(indio_dev);
365 mutex_lock(&state->lock);
366 ret = scd4x_read_channel(state, chan->address);
367 mutex_unlock(&state->lock);
369 iio_device_release_direct_mode(indio_dev);
375 case IIO_CHAN_INFO_SCALE:
376 if (chan->type == IIO_CONCENTRATION) {
379 return IIO_VAL_INT_PLUS_MICRO;
380 } else if (chan->type == IIO_TEMP) {
383 return IIO_VAL_FRACTIONAL;
384 } else if (chan->type == IIO_HUMIDITYRELATIVE) {
387 return IIO_VAL_FRACTIONAL;
390 case IIO_CHAN_INFO_OFFSET:
393 return IIO_VAL_INT_PLUS_MICRO;
394 case IIO_CHAN_INFO_CALIBBIAS:
395 mutex_lock(&state->lock);
396 ret = scd4x_read(state, CMD_GET_TEMP_OFFSET, &tmp, sizeof(tmp));
397 mutex_unlock(&state->lock);
401 *val = be16_to_cpu(tmp);
409 static const int scd4x_pressure_calibbias_available[] = {
410 SCD4X_PRESSURE_COMP_MIN_MBAR, 1, SCD4X_PRESSURE_COMP_MAX_MBAR,
413 static int scd4x_read_avail(struct iio_dev *indio_dev, struct iio_chan_spec const *chan,
414 const int **vals, int *type, int *length, long mask)
417 case IIO_CHAN_INFO_RAW:
418 *vals = scd4x_pressure_calibbias_available;
421 return IIO_AVAIL_RANGE;
428 static int scd4x_write_raw(struct iio_dev *indio_dev, struct iio_chan_spec const *chan,
429 int val, int val2, long mask)
431 struct scd4x_state *state = iio_priv(indio_dev);
435 case IIO_CHAN_INFO_CALIBBIAS:
436 mutex_lock(&state->lock);
437 ret = scd4x_write(state, CMD_SET_TEMP_OFFSET, val);
438 mutex_unlock(&state->lock);
441 case IIO_CHAN_INFO_RAW:
442 switch (chan->type) {
444 if (val < SCD4X_PRESSURE_COMP_MIN_MBAR ||
445 val > SCD4X_PRESSURE_COMP_MAX_MBAR)
448 mutex_lock(&state->lock);
449 ret = scd4x_write(state, CMD_SET_AMB_PRESSURE, val);
450 mutex_unlock(&state->lock);
461 static ssize_t calibration_auto_enable_show(struct device *dev,
462 struct device_attribute *attr, char *buf)
464 struct iio_dev *indio_dev = dev_to_iio_dev(dev);
465 struct scd4x_state *state = iio_priv(indio_dev);
470 mutex_lock(&state->lock);
471 ret = scd4x_read(state, CMD_GET_ASC, &bval, sizeof(bval));
472 mutex_unlock(&state->lock);
474 dev_err(dev, "failed to read automatic calibration");
478 val = (be16_to_cpu(bval) & SCD4X_READY_MASK) ? 1 : 0;
480 return sysfs_emit(buf, "%d\n", val);
483 static ssize_t calibration_auto_enable_store(struct device *dev,
484 struct device_attribute *attr,
485 const char *buf, size_t len)
487 struct iio_dev *indio_dev = dev_to_iio_dev(dev);
488 struct scd4x_state *state = iio_priv(indio_dev);
493 ret = kstrtobool(buf, &val);
499 mutex_lock(&state->lock);
500 ret = scd4x_write(state, CMD_SET_ASC, value);
501 mutex_unlock(&state->lock);
503 dev_err(dev, "failed to set automatic calibration");
508 static ssize_t calibration_forced_value_store(struct device *dev,
509 struct device_attribute *attr,
510 const char *buf, size_t len)
512 struct iio_dev *indio_dev = dev_to_iio_dev(dev);
513 struct scd4x_state *state = iio_priv(indio_dev);
517 ret = kstrtou16(buf, 0, &arg);
521 if (arg < SCD4X_FRC_MIN_PPM || arg > SCD4X_FRC_MAX_PPM)
524 mutex_lock(&state->lock);
525 ret = scd4x_write_and_fetch(state, CMD_FRC, arg, &val, sizeof(val));
526 mutex_unlock(&state->lock);
532 dev_err(dev, "forced calibration has failed");
539 static IIO_DEVICE_ATTR_RW(calibration_auto_enable, 0);
540 static IIO_DEVICE_ATTR_WO(calibration_forced_value, 0);
542 static IIO_CONST_ATTR(calibration_forced_value_available,
543 __stringify([SCD4X_FRC_MIN_PPM 1 SCD4X_FRC_MAX_PPM]));
545 static struct attribute *scd4x_attrs[] = {
546 &iio_dev_attr_calibration_auto_enable.dev_attr.attr,
547 &iio_dev_attr_calibration_forced_value.dev_attr.attr,
548 &iio_const_attr_calibration_forced_value_available.dev_attr.attr,
552 static const struct attribute_group scd4x_attr_group = {
553 .attrs = scd4x_attrs,
556 static const struct iio_info scd4x_info = {
557 .attrs = &scd4x_attr_group,
558 .read_raw = scd4x_read_raw,
559 .write_raw = scd4x_write_raw,
560 .read_avail = scd4x_read_avail,
563 static const struct iio_chan_spec scd4x_channels[] = {
566 * this channel is special in a sense we are pretending that
567 * sensor is able to change measurement chamber pressure but in
568 * fact we're just setting pressure compensation value
570 .type = IIO_PRESSURE,
571 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
572 .info_mask_separate_available = BIT(IIO_CHAN_INFO_RAW),
577 .type = IIO_CONCENTRATION,
578 .channel2 = IIO_MOD_CO2,
580 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
581 BIT(IIO_CHAN_INFO_SCALE),
582 .address = SCD4X_CO2,
583 .scan_index = SCD4X_CO2,
588 .endianness = IIO_BE,
593 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
594 BIT(IIO_CHAN_INFO_SCALE) |
595 BIT(IIO_CHAN_INFO_OFFSET) |
596 BIT(IIO_CHAN_INFO_CALIBBIAS),
597 .address = SCD4X_TEMP,
598 .scan_index = SCD4X_TEMP,
603 .endianness = IIO_BE,
607 .type = IIO_HUMIDITYRELATIVE,
608 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
609 BIT(IIO_CHAN_INFO_SCALE),
611 .scan_index = SCD4X_HR,
616 .endianness = IIO_BE,
621 static int scd4x_suspend(struct device *dev)
623 struct iio_dev *indio_dev = dev_get_drvdata(dev);
624 struct scd4x_state *state = iio_priv(indio_dev);
627 ret = scd4x_send_command(state, CMD_STOP_MEAS);
631 return regulator_disable(state->vdd);
634 static int scd4x_resume(struct device *dev)
636 struct iio_dev *indio_dev = dev_get_drvdata(dev);
637 struct scd4x_state *state = iio_priv(indio_dev);
640 ret = regulator_enable(state->vdd);
644 return scd4x_send_command(state, CMD_START_MEAS);
647 static DEFINE_SIMPLE_DEV_PM_OPS(scd4x_pm_ops, scd4x_suspend, scd4x_resume);
649 static void scd4x_stop_meas(void *state)
651 scd4x_send_command(state, CMD_STOP_MEAS);
654 static void scd4x_disable_regulator(void *data)
656 struct scd4x_state *state = data;
658 regulator_disable(state->vdd);
661 static irqreturn_t scd4x_trigger_handler(int irq, void *p)
663 struct iio_poll_func *pf = p;
664 struct iio_dev *indio_dev = pf->indio_dev;
665 struct scd4x_state *state = iio_priv(indio_dev);
668 int64_t ts __aligned(8);
672 memset(&scan, 0, sizeof(scan));
673 mutex_lock(&state->lock);
674 ret = scd4x_read_poll(state, scan.data);
675 mutex_unlock(&state->lock);
679 iio_push_to_buffers_with_timestamp(indio_dev, &scan, iio_get_time_ns(indio_dev));
681 iio_trigger_notify_done(indio_dev->trig);
685 static int scd4x_probe(struct i2c_client *client)
687 static const unsigned long scd4x_scan_masks[] = { 0x07, 0x00 };
688 struct device *dev = &client->dev;
689 struct iio_dev *indio_dev;
690 struct scd4x_state *state;
693 indio_dev = devm_iio_device_alloc(dev, sizeof(*state));
697 state = iio_priv(indio_dev);
698 mutex_init(&state->lock);
699 state->client = client;
700 crc8_populate_msb(scd4x_crc8_table, SCD4X_CRC8_POLYNOMIAL);
702 indio_dev->info = &scd4x_info;
703 indio_dev->name = client->name;
704 indio_dev->channels = scd4x_channels;
705 indio_dev->num_channels = ARRAY_SIZE(scd4x_channels);
706 indio_dev->modes = INDIO_DIRECT_MODE;
707 indio_dev->available_scan_masks = scd4x_scan_masks;
709 state->vdd = devm_regulator_get(dev, "vdd");
710 if (IS_ERR(state->vdd))
711 return dev_err_probe(dev, PTR_ERR(state->vdd), "failed to get regulator\n");
713 ret = regulator_enable(state->vdd);
717 ret = devm_add_action_or_reset(dev, scd4x_disable_regulator, state);
721 ret = scd4x_send_command(state, CMD_STOP_MEAS);
723 dev_err(dev, "failed to stop measurement: %d\n", ret);
728 msleep_interruptible(500);
730 ret = devm_iio_triggered_buffer_setup(dev, indio_dev, NULL, scd4x_trigger_handler, NULL);
734 ret = scd4x_send_command(state, CMD_START_MEAS);
736 dev_err(dev, "failed to start measurement: %d\n", ret);
740 ret = devm_add_action_or_reset(dev, scd4x_stop_meas, state);
744 return devm_iio_device_register(dev, indio_dev);
747 static const struct of_device_id scd4x_dt_ids[] = {
748 { .compatible = "sensirion,scd40" },
749 { .compatible = "sensirion,scd41" },
752 MODULE_DEVICE_TABLE(of, scd4x_dt_ids);
754 static struct i2c_driver scd4x_i2c_driver = {
756 .name = KBUILD_MODNAME,
757 .of_match_table = scd4x_dt_ids,
758 .pm = pm_sleep_ptr(&scd4x_pm_ops),
760 .probe = scd4x_probe,
762 module_i2c_driver(scd4x_i2c_driver);
764 MODULE_AUTHOR("Roan van Dijk <roan@protonic.nl>");
765 MODULE_DESCRIPTION("Sensirion SCD4X carbon dioxide sensor core driver");
766 MODULE_LICENSE("GPL v2");