This driver handles DHT11 and DHT22 sensors.
Signed-off-by: Harald Geyer <harald@xxxxxxxxx>
---
changes since v2 (tested on DHT22):
Remove some comments
Use devm_iio_device_register()
Rename driver: dht11-gpio -> dht11
Move from INIT_COMPLETION to reinit_completion()
changes since v1 (tested on DHT11):
Add dependency on GPIOLIB
Prefix all local preprocessor macros with DHT11_
Rename STARTUP to START_TRANSMISSION
Remove leading zeros
Simplify channel disambiguation
Remove obvious comments
Make whitespace more consistent
Strip unnecessary output and simplify error handling
Fix spelling errors
The v1 patch has been tested with DHT11 and DHT22 hardware.
Thanks,
Harald
.../devicetree/bindings/iio/humidity/dht11.txt | 14 +
drivers/iio/Kconfig | 1 +
drivers/iio/Makefile | 1 +
drivers/iio/humidity/Kconfig | 15 +
drivers/iio/humidity/Makefile | 5 +
drivers/iio/humidity/dht11.c | 295 ++++++++++++++++++++
6 files changed, 331 insertions(+), 0 deletions(-)
create mode 100644 Documentation/devicetree/bindings/iio/humidity/dht11.txt
create mode 100644 drivers/iio/humidity/Kconfig
create mode 100644 drivers/iio/humidity/Makefile
create mode 100644 drivers/iio/humidity/dht11.c
diff --git a/Documentation/devicetree/bindings/iio/humidity/dht11.txt b/Documentation/devicetree/bindings/iio/humidity/dht11.txt
new file mode 100644
index 0000000..ecc24c19
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/humidity/dht11.txt
@@ -0,0 +1,14 @@
+* DHT11 humidity/temperature sensor (and compatibles like DHT22)
+
+Required properties:
+ - compatible: Should be "dht11"
+ - gpios: Should specify the GPIO connected to the sensor's data
+ line, see "gpios property" in
+ Documentation/devicetree/bindings/gpio/gpio.txt.
+
+Example:
+
+humidity_sensor {
+ compatible = "dht11";
+ gpios = <&gpio0 6 0>;
+}
diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
index 90cf0cd..a5ed882 100644
--- a/drivers/iio/Kconfig
+++ b/drivers/iio/Kconfig
@@ -65,6 +65,7 @@ source "drivers/iio/common/Kconfig"
source "drivers/iio/dac/Kconfig"
source "drivers/iio/frequency/Kconfig"
source "drivers/iio/gyro/Kconfig"
+source "drivers/iio/humidity/Kconfig"
source "drivers/iio/imu/Kconfig"
source "drivers/iio/light/Kconfig"
source "drivers/iio/magnetometer/Kconfig"
diff --git a/drivers/iio/Makefile b/drivers/iio/Makefile
index bcf7e9e..b3b5096 100644
--- a/drivers/iio/Makefile
+++ b/drivers/iio/Makefile
@@ -18,6 +18,7 @@ obj-y += common/
obj-y += dac/
obj-y += gyro/
obj-y += frequency/
+obj-y += humidity/
obj-y += imu/
obj-y += light/
obj-y += magnetometer/
diff --git a/drivers/iio/humidity/Kconfig b/drivers/iio/humidity/Kconfig
new file mode 100644
index 0000000..463c4d9
--- /dev/null
+++ b/drivers/iio/humidity/Kconfig
@@ -0,0 +1,15 @@
+#
+# humidity sensor drivers
+#
+menu "Humidity sensors"
+
+config DHT11
+ tristate "DHT11 (and compatible sensors) driver"
+ depends on GPIOLIB
+ help
+ This driver supports reading data via a single interrupt
+ generating GPIO line. Currently tested are DHT11 and DHT22.
+ Other sensors should work as well as long as they speak the
+ same protocol.
+
+endmenu
diff --git a/drivers/iio/humidity/Makefile b/drivers/iio/humidity/Makefile
new file mode 100644
index 0000000..d5d36c0
--- /dev/null
+++ b/drivers/iio/humidity/Makefile
@@ -0,0 +1,5 @@
+#
+# Makefile for IIO humidity sensor drivers
+#
+
+obj-$(CONFIG_DHT11) += dht11.o
diff --git a/drivers/iio/humidity/dht11.c b/drivers/iio/humidity/dht11.c
new file mode 100644
index 0000000..248f0da
--- /dev/null
+++ b/drivers/iio/humidity/dht11.c
@@ -0,0 +1,295 @@
+/*
+ * DHT11/DHT22 bit banging GPIO driver
+ *
+ * Copyright (c) Harald Geyer <harald@xxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/printk.h>
+#include <linux/slab.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/sysfs.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/wait.h>
+#include <linux/bitops.h>
+#include <linux/completion.h>
+#include <linux/delay.h>
+#include <linux/gpio.h>
+#include <linux/of_gpio.h>
+
+#include <linux/iio/iio.h>
+
+#define DRIVER_NAME "dht11"
+
+#define DHT11_DATA_VALID_TIME 2000000000 /* 2s in ns */
+
+#define DHT11_EDGES_PREAMBLE 4
+#define DHT11_BITS_PER_READ 40
+#define DHT11_EDGES_PER_READ (2*DHT11_BITS_PER_READ + DHT11_EDGES_PREAMBLE + 1)
+
+/* Data transmission timing (nano seconds) */
+#define DHT11_START_TRANSMISSION 18 /* ms */
+#define DHT11_SENSOR_RESPONSE 80000
+#define DHT11_START_BIT 50000
+#define DHT11_DATA_BIT_LOW 27000
+#define DHT11_DATA_BIT_HIGH 70000
+
+struct dht11 {
+ struct device *dev;
+
+ int gpio;
+ int irq;
+
+ struct completion completion;
+
+ s64 timestamp;
+ int temperature;
+ int humidity;
+
+ /* num_edges: -1 means "no transmission in progress" */
+ int num_edges;
+ struct {s64 ts; int value; } edges[DHT11_EDGES_PER_READ];
+};
+
+static unsigned char dht11_decode_byte(int *timing, int threshold)
+{
+ unsigned char ret = 0;
+ int i;
+
+ for (i = 0; i < 8; ++i) {
+ ret <<= 1;
+ if (timing[i] >= threshold)
+ ++ret;
+ }
+
+ return ret;
+}
+
+static int dht11_decode(struct dht11 *dht11, int offset)
+{
+ int i, t, timing[DHT11_BITS_PER_READ], threshold,
+ timeres = DHT11_SENSOR_RESPONSE;
+ unsigned char temp_int, temp_dec, hum_int, hum_dec, checksum;
+
+ /* Calculate timestamp resolution */
+ for (i = 0; i < dht11->num_edges; ++i) {
+ t = dht11->edges[i].ts - dht11->edges[i-1].ts;
+ if (t > 0 && t < timeres)
+ timeres = t;
+ }
+ if (2*timeres > DHT11_DATA_BIT_HIGH) {
+ pr_err("dht11: timeresolution %d too bad for decoding\n",
+ timeres);
+ return -EIO;
+ }
+ threshold = DHT11_DATA_BIT_HIGH / timeres;
+ if (DHT11_DATA_BIT_LOW/timeres + 1 >= threshold)
+ pr_err("dht11: WARNING: decoding ambiguous\n");
+
+ /* scale down with timeres and check validity */
+ for (i = 0; i < DHT11_BITS_PER_READ; ++i) {
+ t = dht11->edges[offset + 2*i + 2].ts -
+ dht11->edges[offset + 2*i + 1].ts;
+ if (!dht11->edges[offset + 2*i + 1].value)
+ return -EIO; /* lost synchronisation */
+ timing[i] = t / timeres;
+ }
+
+ hum_int = dht11_decode_byte(timing, threshold);
+ hum_dec = dht11_decode_byte(&timing[8], threshold);
+ temp_int = dht11_decode_byte(&timing[16], threshold);
+ temp_dec = dht11_decode_byte(&timing[24], threshold);
+ checksum = dht11_decode_byte(&timing[32], threshold);
+
+ if (((hum_int + hum_dec + temp_int + temp_dec) & 0xff) != checksum)
+ return -EIO;
+
+ dht11->timestamp = iio_get_time_ns();
+ if (hum_int < 20) { /* DHT22 */
+ dht11->temperature = (((temp_int & 0x7f) << 8) + temp_dec) *
+ ((temp_int & 0x80) ? -100 : 100);
+ dht11->humidity = ((hum_int << 8) + hum_dec) * 100;
+ } else if (temp_dec == 0 && hum_dec == 0) { /* DHT11 */
+ dht11->temperature = temp_int * 1000;
+ dht11->humidity = hum_int * 1000;
+ } else {
+ dev_err(dht11->dev,
+ "Don't know how to decode data: %d %d %d %d\n",
+ hum_int, hum_dec, temp_int, temp_dec);
+ return -EIO;
+ }
+
+ return 0;
+}
+
+static int dht11_read_raw(struct iio_dev *iio_dev,
+ const struct iio_chan_spec *chan,
+ int *val, int *val2, long m)
+{
+ struct dht11 *dht11 = iio_priv(iio_dev);
+ int ret;
+
+ if (dht11->timestamp + DHT11_DATA_VALID_TIME < iio_get_time_ns()) {
+ reinit_completion(&dht11->completion);
+
+ dht11->num_edges = 0;
+ ret = gpio_direction_output(dht11->gpio, 0);
+ if (ret)
+ goto err;
+ msleep(DHT11_START_TRANSMISSION);
+ ret = gpio_direction_input(dht11->gpio);
+ if (ret)
+ goto err;
+
+ ret = wait_for_completion_killable_timeout(&dht11->completion,
+ HZ);
+ if (ret == 0 && dht11->num_edges < DHT11_EDGES_PER_READ - 1) {
+ dev_err(&iio_dev->dev,
+ "Only %d signal edges detected\n",
+ dht11->num_edges);
+ ret = -ETIMEDOUT;
+ }
+ if (ret < 0)
+ goto err;
+
+ ret = dht11_decode(dht11,
+ dht11->num_edges == DHT11_EDGES_PER_READ ?
+ DHT11_EDGES_PREAMBLE :
+ DHT11_EDGES_PREAMBLE - 2);
+ if (ret)
+ goto err;
+ }
+
+ ret = IIO_VAL_INT;
+ if (chan->type == IIO_TEMP)
+ *val = dht11->temperature;
+ else if (chan->type == IIO_HUMIDITYRELATIVE)
+ *val = dht11->humidity;
+ else
+ ret = -EINVAL;
+err:
+ dht11->num_edges = -1;
+ return ret;
+}
+
+static const struct iio_info dht11_iio_info = {
+ .driver_module = THIS_MODULE,
+ .read_raw = dht11_read_raw,
+};
+
+/*
+ * IRQ handler called on GPIO edges
+*/
+static irqreturn_t dht11_handle_irq(int irq, void *data)
+{
+ struct iio_dev *iio = data;
+ struct dht11 *dht11 = iio_priv(iio);
+
+ /* TODO: Consider making the handler safe for IRQ sharing */
+ if (dht11->num_edges < DHT11_EDGES_PER_READ && dht11->num_edges >= 0) {
+ dht11->edges[dht11->num_edges].ts = iio_get_time_ns();
+ dht11->edges[dht11->num_edges++].value =
+ gpio_get_value(dht11->gpio);
+
+ if (dht11->num_edges >= DHT11_EDGES_PER_READ)
+ complete(&dht11->completion);
+ }
+
+ return IRQ_HANDLED;
+}
+
+static const struct iio_chan_spec dht11_chan_spec[] = {
+ { .type = IIO_TEMP,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), },
+ { .type = IIO_HUMIDITYRELATIVE,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), }
+};
+
+static const struct of_device_id dht11_dt_ids[] = {
+ { .compatible = "dht11", },
+ { }
+};
+MODULE_DEVICE_TABLE(of, dht11_dt_ids);
+
+static int dht11_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct device_node *node = dev->of_node;
+ struct dht11 *dht11;
+ struct iio_dev *iio;
+ int ret;
+
+ iio = devm_iio_device_alloc(dev, sizeof(*dht11));
+ if (!iio) {
+ dev_err(dev, "Failed to allocate IIO device\n");
+ return -ENOMEM;
+ }
+
+ dht11 = iio_priv(iio);
+ dht11->dev = dev;
+
+ dht11->gpio = ret = of_get_gpio(node, 0);
+ if (ret < 0)
+ return ret;
+ ret = devm_gpio_request_one(dev, dht11->gpio, GPIOF_IN, pdev->name);
+ if (ret)
+ return ret;
+
+ dht11->irq = gpio_to_irq(dht11->gpio);
+ if (dht11->irq < 0) {
+ dev_err(dev, "GPIO %d has no interrupt\n", dht11->gpio);
+ return -EINVAL;
+ }
+ ret = devm_request_irq(dev, dht11->irq, dht11_handle_irq,
+ IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
+ pdev->name, iio);
+ if (ret)
+ return ret;
+
+ dht11->timestamp = iio_get_time_ns() - DHT11_DATA_VALID_TIME - 1;
+ dht11->num_edges = -1;
+
+ platform_set_drvdata(pdev, iio);
+
+ init_completion(&dht11->completion);
+ iio->name = pdev->name;
+ iio->dev.parent = &pdev->dev;
+ iio->info = &dht11_iio_info;
+ iio->modes = INDIO_DIRECT_MODE;
+ iio->channels = dht11_chan_spec;
+ iio->num_channels = ARRAY_SIZE(dht11_chan_spec);
+
+ return devm_iio_device_register(dev, iio);
+}
+
+static struct platform_driver dht11_driver = {
+ .driver = {
+ .name = DRIVER_NAME,
+ .owner = THIS_MODULE,
+ .of_match_table = dht11_dt_ids,
+ },
+ .probe = dht11_probe,
+};
+
+module_platform_driver(dht11_driver);
+
+MODULE_AUTHOR("Harald Geyer <harald@xxxxxxxxx>");
+MODULE_DESCRIPTION("DHT11 humidity/temperature sensor driver");
+MODULE_LICENSE("GPL v2");
+
--
1.7.2.5
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