summaryrefslogtreecommitdiffstats
path: root/drivers/iio/proximity/srf04.c
diff options
context:
space:
mode:
Diffstat (limited to 'drivers/iio/proximity/srf04.c')
-rw-r--r--drivers/iio/proximity/srf04.c304
1 files changed, 304 insertions, 0 deletions
diff --git a/drivers/iio/proximity/srf04.c b/drivers/iio/proximity/srf04.c
new file mode 100644
index 000000000..0428a0dfc
--- /dev/null
+++ b/drivers/iio/proximity/srf04.c
@@ -0,0 +1,304 @@
+/*
+ * SRF04: ultrasonic sensor for distance measuring by using GPIOs
+ *
+ * Copyright (c) 2017 Andreas Klinger <ak@it-klinger.de>
+ *
+ * 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.
+ *
+ * For details about the device see:
+ * http://www.robot-electronics.co.uk/htm/srf04tech.htm
+ *
+ * the measurement cycle as timing diagram looks like:
+ *
+ * +---+
+ * GPIO | |
+ * trig: --+ +------------------------------------------------------
+ * ^ ^
+ * |<->|
+ * udelay(10)
+ *
+ * ultra +-+ +-+ +-+
+ * sonic | | | | | |
+ * burst: ---------+ +-+ +-+ +-----------------------------------------
+ * .
+ * ultra . +-+ +-+ +-+
+ * sonic . | | | | | |
+ * echo: ----------------------------------+ +-+ +-+ +----------------
+ * . .
+ * +------------------------+
+ * GPIO | |
+ * echo: -------------------+ +---------------
+ * ^ ^
+ * interrupt interrupt
+ * (ts_rising) (ts_falling)
+ * |<---------------------->|
+ * pulse time measured
+ * --> one round trip of ultra sonic waves
+ */
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/sched.h>
+#include <linux/interrupt.h>
+#include <linux/delay.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+
+struct srf04_data {
+ struct device *dev;
+ struct gpio_desc *gpiod_trig;
+ struct gpio_desc *gpiod_echo;
+ struct mutex lock;
+ int irqnr;
+ ktime_t ts_rising;
+ ktime_t ts_falling;
+ struct completion rising;
+ struct completion falling;
+};
+
+static irqreturn_t srf04_handle_irq(int irq, void *dev_id)
+{
+ struct iio_dev *indio_dev = dev_id;
+ struct srf04_data *data = iio_priv(indio_dev);
+ ktime_t now = ktime_get();
+
+ if (gpiod_get_value(data->gpiod_echo)) {
+ data->ts_rising = now;
+ complete(&data->rising);
+ } else {
+ data->ts_falling = now;
+ complete(&data->falling);
+ }
+
+ return IRQ_HANDLED;
+}
+
+static int srf04_read(struct srf04_data *data)
+{
+ int ret;
+ ktime_t ktime_dt;
+ u64 dt_ns;
+ u32 time_ns, distance_mm;
+
+ /*
+ * just one read-echo-cycle can take place at a time
+ * ==> lock against concurrent reading calls
+ */
+ mutex_lock(&data->lock);
+
+ reinit_completion(&data->rising);
+ reinit_completion(&data->falling);
+
+ gpiod_set_value(data->gpiod_trig, 1);
+ udelay(10);
+ gpiod_set_value(data->gpiod_trig, 0);
+
+ /* it should not take more than 20 ms until echo is rising */
+ ret = wait_for_completion_killable_timeout(&data->rising, HZ/50);
+ if (ret < 0) {
+ mutex_unlock(&data->lock);
+ return ret;
+ } else if (ret == 0) {
+ mutex_unlock(&data->lock);
+ return -ETIMEDOUT;
+ }
+
+ /* it cannot take more than 50 ms until echo is falling */
+ ret = wait_for_completion_killable_timeout(&data->falling, HZ/20);
+ if (ret < 0) {
+ mutex_unlock(&data->lock);
+ return ret;
+ } else if (ret == 0) {
+ mutex_unlock(&data->lock);
+ return -ETIMEDOUT;
+ }
+
+ ktime_dt = ktime_sub(data->ts_falling, data->ts_rising);
+
+ mutex_unlock(&data->lock);
+
+ dt_ns = ktime_to_ns(ktime_dt);
+ /*
+ * measuring more than 6,45 meters is beyond the capabilities of
+ * the supported sensors
+ * ==> filter out invalid results for not measuring echos of
+ * another us sensor
+ *
+ * formula:
+ * distance 6,45 * 2 m
+ * time = ---------- = ------------ = 40438871 ns
+ * speed 319 m/s
+ *
+ * using a minimum speed at -20 °C of 319 m/s
+ */
+ if (dt_ns > 40438871)
+ return -EIO;
+
+ time_ns = dt_ns;
+
+ /*
+ * the speed as function of the temperature is approximately:
+ *
+ * speed = 331,5 + 0,6 * Temp
+ * with Temp in °C
+ * and speed in m/s
+ *
+ * use 343,5 m/s as ultrasonic speed at 20 °C here in absence of the
+ * temperature
+ *
+ * therefore:
+ * time 343,5 time * 106
+ * distance = ------ * ------- = ------------
+ * 10^6 2 617176
+ * with time in ns
+ * and distance in mm (one way)
+ *
+ * because we limit to 6,45 meters the multiplication with 106 just
+ * fits into 32 bit
+ */
+ distance_mm = time_ns * 106 / 617176;
+
+ return distance_mm;
+}
+
+static int srf04_read_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *channel, int *val,
+ int *val2, long info)
+{
+ struct srf04_data *data = iio_priv(indio_dev);
+ int ret;
+
+ if (channel->type != IIO_DISTANCE)
+ return -EINVAL;
+
+ switch (info) {
+ case IIO_CHAN_INFO_RAW:
+ ret = srf04_read(data);
+ if (ret < 0)
+ return ret;
+ *val = ret;
+ return IIO_VAL_INT;
+ case IIO_CHAN_INFO_SCALE:
+ /*
+ * theoretical maximum resolution is 3 mm
+ * 1 LSB is 1 mm
+ */
+ *val = 0;
+ *val2 = 1000;
+ return IIO_VAL_INT_PLUS_MICRO;
+ default:
+ return -EINVAL;
+ }
+}
+
+static const struct iio_info srf04_iio_info = {
+ .read_raw = srf04_read_raw,
+};
+
+static const struct iio_chan_spec srf04_chan_spec[] = {
+ {
+ .type = IIO_DISTANCE,
+ .info_mask_separate =
+ BIT(IIO_CHAN_INFO_RAW) |
+ BIT(IIO_CHAN_INFO_SCALE),
+ },
+};
+
+static int srf04_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct srf04_data *data;
+ struct iio_dev *indio_dev;
+ int ret;
+
+ indio_dev = devm_iio_device_alloc(dev, sizeof(struct srf04_data));
+ if (!indio_dev) {
+ dev_err(dev, "failed to allocate IIO device\n");
+ return -ENOMEM;
+ }
+
+ data = iio_priv(indio_dev);
+ data->dev = dev;
+
+ mutex_init(&data->lock);
+ init_completion(&data->rising);
+ init_completion(&data->falling);
+
+ data->gpiod_trig = devm_gpiod_get(dev, "trig", GPIOD_OUT_LOW);
+ if (IS_ERR(data->gpiod_trig)) {
+ dev_err(dev, "failed to get trig-gpios: err=%ld\n",
+ PTR_ERR(data->gpiod_trig));
+ return PTR_ERR(data->gpiod_trig);
+ }
+
+ data->gpiod_echo = devm_gpiod_get(dev, "echo", GPIOD_IN);
+ if (IS_ERR(data->gpiod_echo)) {
+ dev_err(dev, "failed to get echo-gpios: err=%ld\n",
+ PTR_ERR(data->gpiod_echo));
+ return PTR_ERR(data->gpiod_echo);
+ }
+
+ if (gpiod_cansleep(data->gpiod_echo)) {
+ dev_err(data->dev, "cansleep-GPIOs not supported\n");
+ return -ENODEV;
+ }
+
+ data->irqnr = gpiod_to_irq(data->gpiod_echo);
+ if (data->irqnr < 0) {
+ dev_err(data->dev, "gpiod_to_irq: %d\n", data->irqnr);
+ return data->irqnr;
+ }
+
+ ret = devm_request_irq(dev, data->irqnr, srf04_handle_irq,
+ IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
+ pdev->name, indio_dev);
+ if (ret < 0) {
+ dev_err(data->dev, "request_irq: %d\n", ret);
+ return ret;
+ }
+
+ platform_set_drvdata(pdev, indio_dev);
+
+ indio_dev->name = "srf04";
+ indio_dev->dev.parent = &pdev->dev;
+ indio_dev->info = &srf04_iio_info;
+ indio_dev->modes = INDIO_DIRECT_MODE;
+ indio_dev->channels = srf04_chan_spec;
+ indio_dev->num_channels = ARRAY_SIZE(srf04_chan_spec);
+
+ return devm_iio_device_register(dev, indio_dev);
+}
+
+static const struct of_device_id of_srf04_match[] = {
+ { .compatible = "devantech,srf04", },
+ {},
+};
+
+MODULE_DEVICE_TABLE(of, of_srf04_match);
+
+static struct platform_driver srf04_driver = {
+ .probe = srf04_probe,
+ .driver = {
+ .name = "srf04-gpio",
+ .of_match_table = of_srf04_match,
+ },
+};
+
+module_platform_driver(srf04_driver);
+
+MODULE_AUTHOR("Andreas Klinger <ak@it-klinger.de>");
+MODULE_DESCRIPTION("SRF04 ultrasonic sensor for distance measuring using GPIOs");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:srf04");
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-23 11:09:57 +0000