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Date: Sun, 14 Nov 2021 14:23:34 +0100
From: Gilles Talis <gilles.talis@...il.com>
To: jic23@...nel.org, lars@...afoo.de, pmeerw@...erw.net,
robh+dt@...nel.org, linux-iio@...r.kernel.org
Cc: devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
Gilles Talis <gilles.talis@...il.com>
Subject: [PATCH 1/2] iio: humidity: Add support for Sensirion SHTC3 sensor
The SHTC3 is a digital humidity and temperature sensor.
It covers humidity measurement range from 0 to 100% relative humidity
and temperature measurement range from -45 to 125 deg C.
Datasheet: https://www.sensirion.com/file/datasheet_shtc3
Signed-off-by: Gilles Talis <gilles.talis@...il.com>
---
drivers/iio/humidity/Kconfig | 11 ++
drivers/iio/humidity/Makefile | 1 +
drivers/iio/humidity/shtc3.c | 286 ++++++++++++++++++++++++++++++++++
3 files changed, 298 insertions(+)
create mode 100644 drivers/iio/humidity/shtc3.c
diff --git a/drivers/iio/humidity/Kconfig b/drivers/iio/humidity/Kconfig
index 2de5494e7c22..7aab6141c64b 100644
--- a/drivers/iio/humidity/Kconfig
+++ b/drivers/iio/humidity/Kconfig
@@ -98,6 +98,17 @@ config HTU21
This driver can also be built as a module. If so, the module will
be called htu21.
+config SHTC3
+ tristate "Sensirion SHTC3 humidity and temperature sensor"
+ depends on I2C
+ select CRC8
+ help
+ Say yes here to build support for the Sensirion SHTC3
+ humidity and temperature sensor.
+
+ To compile this driver as a module, choose M here: the module
+ will be called shtc3.
+
config SI7005
tristate "SI7005 relative humidity and temperature sensor"
depends on I2C
diff --git a/drivers/iio/humidity/Makefile b/drivers/iio/humidity/Makefile
index f19ff3de97c5..13020dfad1b3 100644
--- a/drivers/iio/humidity/Makefile
+++ b/drivers/iio/humidity/Makefile
@@ -16,6 +16,7 @@ obj-$(CONFIG_HTS221_I2C) += hts221_i2c.o
obj-$(CONFIG_HTS221_SPI) += hts221_spi.o
obj-$(CONFIG_HTU21) += htu21.o
+obj-$(CONFIG_SHTC3) += shtc3.o
obj-$(CONFIG_SI7005) += si7005.o
obj-$(CONFIG_SI7020) += si7020.o
diff --git a/drivers/iio/humidity/shtc3.c b/drivers/iio/humidity/shtc3.c
new file mode 100644
index 000000000000..ec3d7215e378
--- /dev/null
+++ b/drivers/iio/humidity/shtc3.c
@@ -0,0 +1,286 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Sensirion SHTC3 Humidity and Temperature Sensor
+ *
+ * Copyright (c) 2021 Gilles Talis <gilles.talis@...il.com>
+ *
+ * Datasheet: https://www.sensirion.com/file/datasheet_shtc3
+ *
+ * I2C slave address: 0x70
+ */
+
+#include <linux/crc8.h>
+#include <linux/delay.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+
+#include <linux/iio/iio.h>
+
+#define SHTC3_CMD(cmd_word) cpu_to_be16(cmd_word)
+#define SHTC3_CMD_LEN 2
+
+#define SHTC3_ID_MASK 0x083F
+#define SHTC3_ID 0x0807
+
+#define SHTC3_CRC8_POLYNOMIAL 0x31
+
+enum shtc3_cmd {
+ SHTC3_CMD_GET_ID = SHTC3_CMD(0xEFC8),
+ SHTC3_CMD_SOFT_RESET = SHTC3_CMD(0x805D),
+ SHTC3_CMD_SLEEP = SHTC3_CMD(0xB098),
+ SHTC3_CMD_WAKEUP = SHTC3_CMD(0x3517),
+ /*
+ * Run measurement, low-power mode, clock stretching
+ * temperature first
+ */
+ SHTC3_CMD_TEMP_MEAS_LP_CS = SHTC3_CMD(0x6458),
+ /*
+ * Run measurement, low-power mode, clock stretching
+ * relative humidity first
+ */
+ SHTC3_CMD_RH_MEAS_LP_CS = SHTC3_CMD(0x44DE),
+};
+
+DECLARE_CRC8_TABLE(shtc3_crc8_tbl);
+
+struct shtc3_rx_data {
+ __be16 data;
+ u8 crc;
+} __packed;
+
+static int shtc3_send_cmd(struct i2c_client *client, u16 cmd, u16 *data)
+{
+ int ret;
+ struct shtc3_rx_data rx_data;
+ u8 crc;
+
+ ret = i2c_master_send(client, (const char *)&cmd, SHTC3_CMD_LEN);
+ if (ret != SHTC3_CMD_LEN)
+ return -EIO;
+
+ /*
+ * This is used to read temperature and humidity measurements
+ * as well as the sensor ID.
+ * Sensor sends 2 bytes of data followed by one byte of CRC
+ */
+ if (data) {
+ ret = i2c_master_recv(client, (u8 *) &rx_data,
+ sizeof(struct shtc3_rx_data));
+ if (ret < 0)
+ return ret;
+ if (ret != sizeof(struct shtc3_rx_data))
+ return -EIO;
+
+ crc = crc8(shtc3_crc8_tbl, (u8 *)&rx_data.data,
+ 2, CRC8_INIT_VALUE);
+ if (crc != rx_data.crc)
+ return -EIO;
+
+ *data = be16_to_cpu(rx_data.data);
+ }
+
+ return 0;
+}
+
+static int shtc3_sleep(struct i2c_client *client)
+{
+ return shtc3_send_cmd(client, SHTC3_CMD_SLEEP, 0);
+}
+
+static int shtc3_wakeup(struct i2c_client *client)
+{
+ if (shtc3_send_cmd(client, SHTC3_CMD_WAKEUP, 0) < 0)
+ return -EIO;
+
+ /* Wait for device to wake up */
+ usleep_range(180, 240);
+
+ return 0;
+}
+
+static int shtc3_read_channel(struct i2c_client *client, bool temp)
+{
+ int ret;
+ u16 cmd;
+ u16 meas;
+
+ ret = shtc3_wakeup(client);
+ if (ret < 0)
+ return ret;
+
+ /*
+ * Sensor sends back measurement results after measurement command
+ * has been issued by the host.
+ * Sensor sends 3 bytes (2 bytes of data + 1 byte of CRC) for each
+ * channel sequentially
+ * The command issued by the host determines the channel for which
+ * the sensor will first send the data.
+ * We select the channel for which we need the results
+ * then only read back the 2 bytes corresponding to this channel.
+ */
+ cmd = temp ? SHTC3_CMD_TEMP_MEAS_LP_CS : SHTC3_CMD_RH_MEAS_LP_CS;
+ ret = shtc3_send_cmd(client, cmd, &meas);
+ if (ret < 0)
+ return ret;
+
+ /* Go back to sleep */
+ shtc3_sleep(client);
+
+ return meas;
+}
+
+static int shtc3_read_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan, int *val,
+ int *val2, long mask)
+{
+ struct i2c_client **client = iio_priv(indio_dev);
+ int ret;
+
+ switch (mask) {
+ case IIO_CHAN_INFO_RAW:
+ ret = shtc3_read_channel(*client, (chan->type == IIO_TEMP));
+ if (ret < 0)
+ return ret;
+ *val = ret;
+ return IIO_VAL_INT;
+ case IIO_CHAN_INFO_SCALE:
+ if (chan->type == IIO_TEMP) {
+ *val = 2;
+ *val2 = 670000;
+ } else {
+ *val = 0;
+ *val2 = 1525;
+ }
+ return IIO_VAL_INT_PLUS_MICRO;
+ case IIO_CHAN_INFO_OFFSET:
+ *val = -16852;
+ return IIO_VAL_INT;
+ default:
+ break;
+ }
+
+ return -EINVAL;
+}
+
+static const struct iio_chan_spec shtc3_channels[] = {
+ {
+ .type = IIO_HUMIDITYRELATIVE,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+ BIT(IIO_CHAN_INFO_SCALE),
+ },
+ {
+ .type = IIO_TEMP,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+ BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET),
+ }
+};
+
+static const struct iio_info shtc3_info = {
+ .read_raw = shtc3_read_raw,
+};
+
+static int shtc3_verify_id(struct i2c_client *client)
+{
+ int ret;
+ u16 device_id;
+ u16 reg_val;
+
+ ret = shtc3_send_cmd(client, SHTC3_CMD_GET_ID, ®_val);
+ if (ret < 0)
+ return ret;
+
+ device_id = reg_val & SHTC3_ID_MASK;
+ if (device_id != SHTC3_ID)
+ return -ENODEV;
+
+ return 0;
+}
+
+static int shtc3_reset(struct i2c_client *client)
+{
+ int ret;
+
+ ret = shtc3_send_cmd(client, SHTC3_CMD_SOFT_RESET, 0);
+ if (ret < 0)
+ return ret;
+
+ /* Wait for device to enter idle state */
+ usleep_range(180, 240);
+
+ return 0;
+}
+
+static int shtc3_setup(struct i2c_client *client)
+{
+ int ret;
+
+ ret = shtc3_verify_id(client);
+ if (ret < 0) {
+ dev_err(&client->dev, "SHTC3 not found\n");
+ return -ENODEV;
+ }
+
+ ret = shtc3_reset(client);
+ if (ret < 0)
+ return ret;
+
+ return shtc3_sleep(client);
+}
+
+static int shtc3_probe(struct i2c_client *client,
+ const struct i2c_device_id *id)
+{
+ struct iio_dev *indio_dev;
+ struct i2c_client **data;
+ int ret;
+
+ indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
+ if (!indio_dev)
+ return -ENOMEM;
+
+ data = iio_priv(indio_dev);
+ *data = client;
+
+ indio_dev->name = dev_name(&client->dev);
+ indio_dev->modes = INDIO_DIRECT_MODE;
+ indio_dev->info = &shtc3_info;
+ indio_dev->channels = shtc3_channels;
+ indio_dev->num_channels = ARRAY_SIZE(shtc3_channels);
+
+ crc8_populate_msb(shtc3_crc8_tbl, SHTC3_CRC8_POLYNOMIAL);
+
+ ret = shtc3_setup(client);
+ if (ret < 0) {
+ dev_err(&client->dev, "SHTC3 setup failed\n");
+ return ret;
+ }
+
+ return devm_iio_device_register(&client->dev, indio_dev);
+}
+
+static const struct i2c_device_id shtc3_id[] = {
+ { "shtc3", 0 },
+ { }
+};
+MODULE_DEVICE_TABLE(i2c, shtc3_id);
+
+static const struct of_device_id shtc3_dt_ids[] = {
+ { .compatible = "sensirion,shtc3" },
+ { }
+};
+MODULE_DEVICE_TABLE(of, shtc3_dt_ids);
+
+static struct i2c_driver shtc3_driver = {
+ .driver = {
+ .name = "shtc3",
+ .of_match_table = shtc3_dt_ids,
+ },
+ .probe = shtc3_probe,
+ .id_table = shtc3_id,
+};
+
+module_i2c_driver(shtc3_driver);
+MODULE_DESCRIPTION("Sensirion SHTC3 Humidity and Temperature Sensor");
+MODULE_AUTHOR("Gilles Talis <gilles.talis@...il.com>");
+MODULE_LICENSE("GPL");
--
2.27.0
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