This is the IIO driver for AVIA HX711 ADC which ist mostly used in weighting
cells.
The protocol is quite simple and using GPIO's:
One GPIO is used as clock (SCK) while another GPIO is read (DOUT)
The raw value read from the chip is delivered.
To get a weight one needs to subtract the zero offset and scale it.
Signed-off-by: Andreas Klinger <a...@it-klinger.de>
---
drivers/iio/adc/Kconfig | 18 ++++
drivers/iio/adc/Makefile | 1 +
drivers/iio/adc/hx711.c | 231 +++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 250 insertions(+)
create mode 100644 drivers/iio/adc/hx711.c
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 932de1f9d1e7..918f582288c9 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -205,6 +205,24 @@ config HI8435
This driver can also be built as a module. If so, the module will be
called hi8435.
+config HX711
+ tristate "AVIA HX711 ADC for weight cells"
+ depends on GPIOLIB
+ help
+ If you say yes here you get support for AVIA HX711 ADC which is used
+ for weight cells
+
+ This driver uses two GPIOs, one for setting the clock and the other
+ one for getting the data
+
+ Currently the raw value is read from the chip and delivered.
+ For getting an actual weight one needs to subtract the
+ zero offset and multiply by a scale factor.
+ This should be done in userspace.
+
+ This driver can also be built as a module. If so, the module will be
+ called hx711.
+
config INA2XX_ADC
tristate "Texas Instruments INA2xx Power Monitors IIO driver"
depends on I2C && !SENSORS_INA2XX
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index b1aa456e6af3..d46e289900ef 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -21,6 +21,7 @@ obj-$(CONFIG_CC10001_ADC) += cc10001_adc.o
obj-$(CONFIG_DA9150_GPADC) += da9150-gpadc.o
obj-$(CONFIG_EXYNOS_ADC) += exynos_adc.o
obj-$(CONFIG_HI8435) += hi8435.o
+obj-$(CONFIG_HX711) += hx711.o
obj-$(CONFIG_IMX7D_ADC) += imx7d_adc.o
obj-$(CONFIG_INA2XX_ADC) += ina2xx-adc.o
obj-$(CONFIG_LP8788_ADC) += lp8788_adc.o
diff --git a/drivers/iio/adc/hx711.c b/drivers/iio/adc/hx711.c
new file mode 100644
index 000000000000..420f9451f3d1
--- /dev/null
+++ b/drivers/iio/adc/hx711.c
@@ -0,0 +1,231 @@
+/*
+ * HX711: analog to digital converter for weight sensor module
+ *
+ * Copyright (c) 2016 Andreas Klinger <a...@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.
+ *
+ */
+#include <linux/err.h>
+#include <linux/gpio.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/slab.h>
+#include <linux/sched.h>
+#include <linux/delay.h>
+#include <linux/iio/iio.h>
+
+#define HX711_GAIN_32 2 /* gain = 32 for channel B */
+#define HX711_GAIN_64 3 /* gain = 64 for channel A */
+#define HX711_GAIN_128 1 /* gain = 128 for channel A */
+
+struct hx711_data {
+ struct device *dev;
+ struct gpio_desc *gpiod_sck;
+ struct gpio_desc *gpiod_dout;
+ int gain_pulse;
+ struct mutex lock;
+};
+
+static int hx711_reset(struct hx711_data *hx711_data)
+{
+ int i, val;
+
+ val = gpiod_get_value(hx711_data->gpiod_dout);
+ if (val) {
+ gpiod_set_value(hx711_data->gpiod_sck, 1);
+ udelay(80);
+ gpiod_set_value(hx711_data->gpiod_sck, 0);
+
+ for (i = 0; i < 1000; i++) {
+ val = gpiod_get_value(hx711_data->gpiod_dout);
+ if (!val)
+ break;
+ /* sleep at least 1 ms */
+ msleep(1);
+ }
+ }
+
+ return val;
+}
+
+static int hx711_cycle(struct hx711_data *hx711_data)
+{
+ int val;
+
+ /* if preempted for more then 60us while SCK is high:
+ * hx711 is going in reset
+ * ==> measuring is false
+ */
+ preempt_disable();
+ gpiod_set_value(hx711_data->gpiod_sck, 1);
+ val = gpiod_get_value(hx711_data->gpiod_dout);
+ gpiod_set_value(hx711_data->gpiod_sck, 0);
+ preempt_enable();
+
+ return val;
+}
+
+static int hx711_read(struct hx711_data *hx711_data)
+{
+ int i, ret;
+ int value = 0;
+
+ if (hx711_reset(hx711_data)) {
+ dev_err(hx711_data->dev, "reset failed!");
+ return -1;
+ }
+
+ for (i = 0; i < 24; i++) {
+ value <<= 1;
+ ret = hx711_cycle(hx711_data);
+ if (ret)
+ value++;
+ }
+
+ value ^= 0x800000;
+
+ for (i = 0; i < hx711_data->gain_pulse; i++)
+ ret = hx711_cycle(hx711_data);
+
+ return value;
+}
+
+static int hx711_read_raw(struct iio_dev *iio_dev,
+ const struct iio_chan_spec *chan,
+ int *val, int *val2, long mask)
+{
+ struct hx711_data *hx711_data = iio_priv(iio_dev);
+
+ switch (mask) {
+ case IIO_CHAN_INFO_RAW:
+ switch (chan->type) {
+ case IIO_VOLTAGE:
+ mutex_lock(&hx711_data->lock);
+ *val = hx711_read(hx711_data);
+ mutex_unlock(&hx711_data->lock);
+ return IIO_VAL_INT;
+ default:
+ return -EINVAL;
+ }
+ default:
+ return -EINVAL;
+ }
+}
+
+static const struct iio_info hx711_iio_info = {
+ .driver_module = THIS_MODULE,
+ .read_raw = hx711_read_raw,
+};
+
+static const struct iio_chan_spec hx711_chan_spec[] = {
+ { .type = IIO_VOLTAGE,
+ .info_mask_separate =
+ BIT(IIO_CHAN_INFO_RAW),
+ },
+};
+
+static int hx711_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct device_node *node = dev->of_node;
+ struct hx711_data *hx711_data = NULL;
+ struct iio_dev *iio;
+ int ret = 0, ival;
+
+ iio = devm_iio_device_alloc(dev, sizeof(struct hx711_data));
+ if (!iio) {
+ dev_err(dev, "failed to allocate IIO device\n");
+ return -ENOMEM;
+ }
+
+ hx711_data = iio_priv(iio);
+ hx711_data->dev = dev;
+
+ mutex_init(&hx711_data->lock);
+
+ hx711_data->gpiod_sck = devm_gpiod_get(dev, "sck", GPIOD_OUT_HIGH);
+ if (IS_ERR(hx711_data->gpiod_sck)) {
+ dev_err(dev, "failed to get sck-gpiod: err=%ld\n",
+ PTR_ERR(hx711_data->gpiod_sck));
+ return PTR_ERR(hx711_data->gpiod_sck);
+ }
+
+ hx711_data->gpiod_dout = devm_gpiod_get(dev, "dout", GPIOD_OUT_HIGH);
+ if (IS_ERR(hx711_data->gpiod_dout)) {
+ dev_err(dev, "failed to get dout-gpiod: err=%ld\n",
+ PTR_ERR(hx711_data->gpiod_dout));
+ return PTR_ERR(hx711_data->gpiod_dout);
+ }
+
+ of_property_read_u32 (node, "gain", &ival);
+ switch (ival) {
+ case 32:
+ hx711_data->gain_pulse = HX711_GAIN_32;
+ break;
+ case 64:
+ hx711_data->gain_pulse = HX711_GAIN_64;
+ break;
+ default:
+ hx711_data->gain_pulse = HX711_GAIN_128;
+ }
+ dev_dbg(hx711_data->dev, "gain: %d\n", hx711_data->gain_pulse);
+
+ ret = gpiod_direction_input(hx711_data->gpiod_dout);
+ if (ret < 0) {
+ dev_err(hx711_data->dev, "gpiod_direction_input: %d\n", ret);
+ return ret;
+ }
+
+ ret = gpiod_direction_output(hx711_data->gpiod_sck, 0);
+ if (ret < 0) {
+ dev_err(hx711_data->dev, "gpiod_direction_output: %d\n", ret);
+ return ret;
+ }
+
+ platform_set_drvdata(pdev, iio);
+
+ iio->name = pdev->name;
+ iio->dev.parent = &pdev->dev;
+ iio->info = &hx711_iio_info;
+ iio->modes = INDIO_DIRECT_MODE;
+ iio->channels = hx711_chan_spec;
+ iio->num_channels = ARRAY_SIZE(hx711_chan_spec);
+
+ return devm_iio_device_register(dev, iio);
+}
+
+static const struct of_device_id of_hx711_match[] = {
+ { .compatible = "avia,hx711", },
+ {},
+};
+
+MODULE_DEVICE_TABLE(of, of_hx711_match);
+
+static struct platform_driver hx711_driver = {
+ .probe = hx711_probe,
+ .driver = {
+ .name = "hx711-gpio",
+ .of_match_table = of_hx711_match,
+ },
+};
+
+module_platform_driver(hx711_driver);
+
+MODULE_AUTHOR("Andreas Klinger <a...@it-klinger.de>");
+MODULE_DESCRIPTION("HX711 bitbanging driver - ADC for weight cells");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:hx711-gpio");
+
--
2.1.4
