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Diffstat (limited to 'drivers/iio/adc/hx711.c')
-rw-r--r--drivers/iio/adc/hx711.c622
1 files changed, 622 insertions, 0 deletions
diff --git a/drivers/iio/adc/hx711.c b/drivers/iio/adc/hx711.c
new file mode 100644
index 0000000000..f7ee856a6b
--- /dev/null
+++ b/drivers/iio/adc/hx711.c
@@ -0,0 +1,622 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * HX711: analog to digital converter for weight sensor module
+ *
+ * Copyright (c) 2016 Andreas Klinger <ak@it-klinger.de>
+ */
+#include <linux/err.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>
+#include <linux/iio/sysfs.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
+#include <linux/gpio/consumer.h>
+#include <linux/regulator/consumer.h>
+
+/* gain to pulse and scale conversion */
+#define HX711_GAIN_MAX 3
+#define HX711_RESET_GAIN 128
+
+struct hx711_gain_to_scale {
+ int gain;
+ int gain_pulse;
+ int scale;
+ int channel;
+};
+
+/*
+ * .scale depends on AVDD which in turn is known as soon as the regulator
+ * is available
+ * therefore we set .scale in hx711_probe()
+ *
+ * channel A in documentation is channel 0 in source code
+ * channel B in documentation is channel 1 in source code
+ */
+static struct hx711_gain_to_scale hx711_gain_to_scale[HX711_GAIN_MAX] = {
+ { 128, 1, 0, 0 },
+ { 32, 2, 0, 1 },
+ { 64, 3, 0, 0 }
+};
+
+static int hx711_get_gain_to_pulse(int gain)
+{
+ int i;
+
+ for (i = 0; i < HX711_GAIN_MAX; i++)
+ if (hx711_gain_to_scale[i].gain == gain)
+ return hx711_gain_to_scale[i].gain_pulse;
+ return 1;
+}
+
+static int hx711_get_gain_to_scale(int gain)
+{
+ int i;
+
+ for (i = 0; i < HX711_GAIN_MAX; i++)
+ if (hx711_gain_to_scale[i].gain == gain)
+ return hx711_gain_to_scale[i].scale;
+ return 0;
+}
+
+static int hx711_get_scale_to_gain(int scale)
+{
+ int i;
+
+ for (i = 0; i < HX711_GAIN_MAX; i++)
+ if (hx711_gain_to_scale[i].scale == scale)
+ return hx711_gain_to_scale[i].gain;
+ return -EINVAL;
+}
+
+struct hx711_data {
+ struct device *dev;
+ struct gpio_desc *gpiod_pd_sck;
+ struct gpio_desc *gpiod_dout;
+ struct regulator *reg_avdd;
+ int gain_set; /* gain set on device */
+ int gain_chan_a; /* gain for channel A */
+ struct mutex lock;
+ /*
+ * triggered buffer
+ * 2x32-bit channel + 64-bit naturally aligned timestamp
+ */
+ u32 buffer[4] __aligned(8);
+ /*
+ * delay after a rising edge on SCK until the data is ready DOUT
+ * this is dependent on the hx711 where the datasheet tells a
+ * maximum value of 100 ns
+ * but also on potential parasitic capacities on the wiring
+ */
+ u32 data_ready_delay_ns;
+ u32 clock_frequency;
+};
+
+static int hx711_cycle(struct hx711_data *hx711_data)
+{
+ unsigned long flags;
+
+ /*
+ * if preempted for more then 60us while PD_SCK is high:
+ * hx711 is going in reset
+ * ==> measuring is false
+ */
+ local_irq_save(flags);
+ gpiod_set_value(hx711_data->gpiod_pd_sck, 1);
+
+ /*
+ * wait until DOUT is ready
+ * it turned out that parasitic capacities are extending the time
+ * until DOUT has reached it's value
+ */
+ ndelay(hx711_data->data_ready_delay_ns);
+
+ /*
+ * here we are not waiting for 0.2 us as suggested by the datasheet,
+ * because the oscilloscope showed in a test scenario
+ * at least 1.15 us for PD_SCK high (T3 in datasheet)
+ * and 0.56 us for PD_SCK low on TI Sitara with 800 MHz
+ */
+ gpiod_set_value(hx711_data->gpiod_pd_sck, 0);
+ local_irq_restore(flags);
+
+ /*
+ * make it a square wave for addressing cases with capacitance on
+ * PC_SCK
+ */
+ ndelay(hx711_data->data_ready_delay_ns);
+
+ /* sample as late as possible */
+ return gpiod_get_value(hx711_data->gpiod_dout);
+}
+
+static int hx711_read(struct hx711_data *hx711_data)
+{
+ int i, ret;
+ int value = 0;
+ int val = gpiod_get_value(hx711_data->gpiod_dout);
+
+ /* we double check if it's really down */
+ if (val)
+ return -EIO;
+
+ for (i = 0; i < 24; i++) {
+ value <<= 1;
+ ret = hx711_cycle(hx711_data);
+ if (ret)
+ value++;
+ }
+
+ value ^= 0x800000;
+
+ for (i = 0; i < hx711_get_gain_to_pulse(hx711_data->gain_set); i++)
+ hx711_cycle(hx711_data);
+
+ return value;
+}
+
+static int hx711_wait_for_ready(struct hx711_data *hx711_data)
+{
+ int i, val;
+
+ /*
+ * in some rare cases the reset takes quite a long time
+ * especially when the channel is changed.
+ * Allow up to one second for it
+ */
+ for (i = 0; i < 100; i++) {
+ val = gpiod_get_value(hx711_data->gpiod_dout);
+ if (!val)
+ break;
+ /* sleep at least 10 ms */
+ msleep(10);
+ }
+ if (val)
+ return -EIO;
+
+ return 0;
+}
+
+static int hx711_reset(struct hx711_data *hx711_data)
+{
+ int val = hx711_wait_for_ready(hx711_data);
+
+ if (val) {
+ /*
+ * an examination with the oszilloscope indicated
+ * that the first value read after the reset is not stable
+ * if we reset too short;
+ * the shorter the reset cycle
+ * the less reliable the first value after reset is;
+ * there were no problems encountered with a value
+ * of 10 ms or higher
+ */
+ gpiod_set_value(hx711_data->gpiod_pd_sck, 1);
+ msleep(10);
+ gpiod_set_value(hx711_data->gpiod_pd_sck, 0);
+
+ val = hx711_wait_for_ready(hx711_data);
+
+ /* after a reset the gain is 128 */
+ hx711_data->gain_set = HX711_RESET_GAIN;
+ }
+
+ return val;
+}
+
+static int hx711_set_gain_for_channel(struct hx711_data *hx711_data, int chan)
+{
+ int ret;
+
+ if (chan == 0) {
+ if (hx711_data->gain_set == 32) {
+ hx711_data->gain_set = hx711_data->gain_chan_a;
+
+ ret = hx711_read(hx711_data);
+ if (ret < 0)
+ return ret;
+
+ ret = hx711_wait_for_ready(hx711_data);
+ if (ret)
+ return ret;
+ }
+ } else {
+ if (hx711_data->gain_set != 32) {
+ hx711_data->gain_set = 32;
+
+ ret = hx711_read(hx711_data);
+ if (ret < 0)
+ return ret;
+
+ ret = hx711_wait_for_ready(hx711_data);
+ if (ret)
+ return ret;
+ }
+ }
+
+ return 0;
+}
+
+static int hx711_reset_read(struct hx711_data *hx711_data, int chan)
+{
+ int ret;
+ int val;
+
+ /*
+ * hx711_reset() must be called from here
+ * because it could be calling hx711_read() by itself
+ */
+ if (hx711_reset(hx711_data)) {
+ dev_err(hx711_data->dev, "reset failed!");
+ return -EIO;
+ }
+
+ ret = hx711_set_gain_for_channel(hx711_data, chan);
+ if (ret < 0)
+ return ret;
+
+ val = hx711_read(hx711_data);
+
+ return val;
+}
+
+static int hx711_read_raw(struct iio_dev *indio_dev,
+ const struct iio_chan_spec *chan,
+ int *val, int *val2, long mask)
+{
+ struct hx711_data *hx711_data = iio_priv(indio_dev);
+
+ switch (mask) {
+ case IIO_CHAN_INFO_RAW:
+ mutex_lock(&hx711_data->lock);
+
+ *val = hx711_reset_read(hx711_data, chan->channel);
+
+ mutex_unlock(&hx711_data->lock);
+
+ if (*val < 0)
+ return *val;
+ return IIO_VAL_INT;
+ case IIO_CHAN_INFO_SCALE:
+ *val = 0;
+ mutex_lock(&hx711_data->lock);
+
+ *val2 = hx711_get_gain_to_scale(hx711_data->gain_set);
+
+ mutex_unlock(&hx711_data->lock);
+
+ return IIO_VAL_INT_PLUS_NANO;
+ default:
+ return -EINVAL;
+ }
+}
+
+static int hx711_write_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int val,
+ int val2,
+ long mask)
+{
+ struct hx711_data *hx711_data = iio_priv(indio_dev);
+ int ret;
+ int gain;
+
+ switch (mask) {
+ case IIO_CHAN_INFO_SCALE:
+ /*
+ * a scale greater than 1 mV per LSB is not possible
+ * with the HX711, therefore val must be 0
+ */
+ if (val != 0)
+ return -EINVAL;
+
+ mutex_lock(&hx711_data->lock);
+
+ gain = hx711_get_scale_to_gain(val2);
+ if (gain < 0) {
+ mutex_unlock(&hx711_data->lock);
+ return gain;
+ }
+
+ if (gain != hx711_data->gain_set) {
+ hx711_data->gain_set = gain;
+ if (gain != 32)
+ hx711_data->gain_chan_a = gain;
+
+ ret = hx711_read(hx711_data);
+ if (ret < 0) {
+ mutex_unlock(&hx711_data->lock);
+ return ret;
+ }
+ }
+
+ mutex_unlock(&hx711_data->lock);
+ return 0;
+ default:
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static int hx711_write_raw_get_fmt(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ long mask)
+{
+ return IIO_VAL_INT_PLUS_NANO;
+}
+
+static irqreturn_t hx711_trigger(int irq, void *p)
+{
+ struct iio_poll_func *pf = p;
+ struct iio_dev *indio_dev = pf->indio_dev;
+ struct hx711_data *hx711_data = iio_priv(indio_dev);
+ int i, j = 0;
+
+ mutex_lock(&hx711_data->lock);
+
+ memset(hx711_data->buffer, 0, sizeof(hx711_data->buffer));
+
+ for (i = 0; i < indio_dev->masklength; i++) {
+ if (!test_bit(i, indio_dev->active_scan_mask))
+ continue;
+
+ hx711_data->buffer[j] = hx711_reset_read(hx711_data,
+ indio_dev->channels[i].channel);
+ j++;
+ }
+
+ iio_push_to_buffers_with_timestamp(indio_dev, hx711_data->buffer,
+ pf->timestamp);
+
+ mutex_unlock(&hx711_data->lock);
+
+ iio_trigger_notify_done(indio_dev->trig);
+
+ return IRQ_HANDLED;
+}
+
+static ssize_t hx711_scale_available_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct iio_dev_attr *iio_attr = to_iio_dev_attr(attr);
+ int channel = iio_attr->address;
+ int i, len = 0;
+
+ for (i = 0; i < HX711_GAIN_MAX; i++)
+ if (hx711_gain_to_scale[i].channel == channel)
+ len += sprintf(buf + len, "0.%09d ",
+ hx711_gain_to_scale[i].scale);
+
+ len += sprintf(buf + len, "\n");
+
+ return len;
+}
+
+static IIO_DEVICE_ATTR(in_voltage0_scale_available, S_IRUGO,
+ hx711_scale_available_show, NULL, 0);
+
+static IIO_DEVICE_ATTR(in_voltage1_scale_available, S_IRUGO,
+ hx711_scale_available_show, NULL, 1);
+
+static struct attribute *hx711_attributes[] = {
+ &iio_dev_attr_in_voltage0_scale_available.dev_attr.attr,
+ &iio_dev_attr_in_voltage1_scale_available.dev_attr.attr,
+ NULL,
+};
+
+static const struct attribute_group hx711_attribute_group = {
+ .attrs = hx711_attributes,
+};
+
+static const struct iio_info hx711_iio_info = {
+ .read_raw = hx711_read_raw,
+ .write_raw = hx711_write_raw,
+ .write_raw_get_fmt = hx711_write_raw_get_fmt,
+ .attrs = &hx711_attribute_group,
+};
+
+static const struct iio_chan_spec hx711_chan_spec[] = {
+ {
+ .type = IIO_VOLTAGE,
+ .channel = 0,
+ .indexed = 1,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
+ .scan_index = 0,
+ .scan_type = {
+ .sign = 'u',
+ .realbits = 24,
+ .storagebits = 32,
+ .endianness = IIO_CPU,
+ },
+ },
+ {
+ .type = IIO_VOLTAGE,
+ .channel = 1,
+ .indexed = 1,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
+ .scan_index = 1,
+ .scan_type = {
+ .sign = 'u',
+ .realbits = 24,
+ .storagebits = 32,
+ .endianness = IIO_CPU,
+ },
+ },
+ IIO_CHAN_SOFT_TIMESTAMP(2),
+};
+
+static int hx711_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct device_node *np = dev->of_node;
+ struct hx711_data *hx711_data;
+ struct iio_dev *indio_dev;
+ int ret;
+ int i;
+
+ indio_dev = devm_iio_device_alloc(dev, sizeof(struct hx711_data));
+ if (!indio_dev) {
+ dev_err(dev, "failed to allocate IIO device\n");
+ return -ENOMEM;
+ }
+
+ hx711_data = iio_priv(indio_dev);
+ hx711_data->dev = dev;
+
+ mutex_init(&hx711_data->lock);
+
+ /*
+ * PD_SCK stands for power down and serial clock input of HX711
+ * in the driver it is an output
+ */
+ hx711_data->gpiod_pd_sck = devm_gpiod_get(dev, "sck", GPIOD_OUT_LOW);
+ if (IS_ERR(hx711_data->gpiod_pd_sck)) {
+ dev_err(dev, "failed to get sck-gpiod: err=%ld\n",
+ PTR_ERR(hx711_data->gpiod_pd_sck));
+ return PTR_ERR(hx711_data->gpiod_pd_sck);
+ }
+
+ /*
+ * DOUT stands for serial data output of HX711
+ * for the driver it is an input
+ */
+ hx711_data->gpiod_dout = devm_gpiod_get(dev, "dout", GPIOD_IN);
+ 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);
+ }
+
+ hx711_data->reg_avdd = devm_regulator_get(dev, "avdd");
+ if (IS_ERR(hx711_data->reg_avdd))
+ return PTR_ERR(hx711_data->reg_avdd);
+
+ ret = regulator_enable(hx711_data->reg_avdd);
+ if (ret < 0)
+ return ret;
+
+ /*
+ * with
+ * full scale differential input range: AVDD / GAIN
+ * full scale output data: 2^24
+ * we can say:
+ * AVDD / GAIN = 2^24
+ * therefore:
+ * 1 LSB = AVDD / GAIN / 2^24
+ * AVDD is in uV, but we need 10^-9 mV
+ * approximately to fit into a 32 bit number:
+ * 1 LSB = (AVDD * 100) / GAIN / 1678 [10^-9 mV]
+ */
+ ret = regulator_get_voltage(hx711_data->reg_avdd);
+ if (ret < 0)
+ goto error_regulator;
+
+ /* we need 10^-9 mV */
+ ret *= 100;
+
+ for (i = 0; i < HX711_GAIN_MAX; i++)
+ hx711_gain_to_scale[i].scale =
+ ret / hx711_gain_to_scale[i].gain / 1678;
+
+ hx711_data->gain_set = 128;
+ hx711_data->gain_chan_a = 128;
+
+ hx711_data->clock_frequency = 400000;
+ ret = of_property_read_u32(np, "clock-frequency",
+ &hx711_data->clock_frequency);
+
+ /*
+ * datasheet says the high level of PD_SCK has a maximum duration
+ * of 50 microseconds
+ */
+ if (hx711_data->clock_frequency < 20000) {
+ dev_warn(dev, "clock-frequency too low - assuming 400 kHz\n");
+ hx711_data->clock_frequency = 400000;
+ }
+
+ hx711_data->data_ready_delay_ns =
+ 1000000000 / hx711_data->clock_frequency;
+
+ platform_set_drvdata(pdev, indio_dev);
+
+ indio_dev->name = "hx711";
+ indio_dev->info = &hx711_iio_info;
+ indio_dev->modes = INDIO_DIRECT_MODE;
+ indio_dev->channels = hx711_chan_spec;
+ indio_dev->num_channels = ARRAY_SIZE(hx711_chan_spec);
+
+ ret = iio_triggered_buffer_setup(indio_dev, iio_pollfunc_store_time,
+ hx711_trigger, NULL);
+ if (ret < 0) {
+ dev_err(dev, "setup of iio triggered buffer failed\n");
+ goto error_regulator;
+ }
+
+ ret = iio_device_register(indio_dev);
+ if (ret < 0) {
+ dev_err(dev, "Couldn't register the device\n");
+ goto error_buffer;
+ }
+
+ return 0;
+
+error_buffer:
+ iio_triggered_buffer_cleanup(indio_dev);
+
+error_regulator:
+ regulator_disable(hx711_data->reg_avdd);
+
+ return ret;
+}
+
+static int hx711_remove(struct platform_device *pdev)
+{
+ struct hx711_data *hx711_data;
+ struct iio_dev *indio_dev;
+
+ indio_dev = platform_get_drvdata(pdev);
+ hx711_data = iio_priv(indio_dev);
+
+ iio_device_unregister(indio_dev);
+
+ iio_triggered_buffer_cleanup(indio_dev);
+
+ regulator_disable(hx711_data->reg_avdd);
+
+ return 0;
+}
+
+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,
+ .remove = hx711_remove,
+ .driver = {
+ .name = "hx711-gpio",
+ .of_match_table = of_hx711_match,
+ },
+};
+
+module_platform_driver(hx711_driver);
+
+MODULE_AUTHOR("Andreas Klinger <ak@it-klinger.de>");
+MODULE_DESCRIPTION("HX711 bitbanging driver - ADC for weight cells");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:hx711-gpio");
+
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-24 14:42:33 +0000