On 05/01/17 17:51, Andreas Klinger wrote: > This is the IIO driver for AVIA HX711 ADC which is mostly used in weighting > cells. > > The protocol is quite simple and using GPIOs: > 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 <ak@xxxxxxxxxxxxx> I think your locking is a little heavy handed, perhaps a follow up patch to relax it a little. I fixed a trivial typo when applying. Applied to the togreg branch of iio.git and pushed out as testing for the autobuilders to play with it. Thanks, Jonathan > --- > drivers/iio/adc/Kconfig | 19 ++ > drivers/iio/adc/Makefile | 1 + > drivers/iio/adc/hx711.c | 531 +++++++++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 551 insertions(+) > create mode 100644 drivers/iio/adc/hx711.c > > diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig > index 932de1f9d1e7..1dcf2ace1697 100644 > --- a/drivers/iio/adc/Kconfig > +++ b/drivers/iio/adc/Kconfig > @@ -205,6 +205,25 @@ 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 weigh cells > + > + This driver uses two GPIOs, one acts as the clock and controls the > + channel selection and gain, the other one is used for the measurement > + data > + > + Currently the raw value is read from the chip and delivered. > + To get 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..e41414556158 > --- /dev/null > +++ b/drivers/iio/adc/hx711.c > @@ -0,0 +1,531 @@ > +/* > + * HX711: analog to digital converter for weight sensor module > + * > + * Copyright (c) 2016 Andreas Klinger <ak@xxxxxxxxxxxxx> > + * > + * 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/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/gpio/consumer.h> > +#include <linux/regulator/consumer.h> > + > +/* gain to pulse and scale conversion */ > +#define HX711_GAIN_MAX 3 > + > +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; > +}; > + > +static int hx711_cycle(struct hx711_data *hx711_data) > +{ > + int val; > + > + /* > + * if preempted for more then 60us while PD_SCK is high: > + * hx711 is going in reset > + * ==> measuring is false > + */ > + preempt_disable(); > + gpiod_set_value(hx711_data->gpiod_pd_sck, 1); > + val = gpiod_get_value(hx711_data->gpiod_dout); > + /* > + * here we are not waiting for 0.2 us as suggested by the datasheet, > + * because the oszilloscope 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); > + preempt_enable(); > + > + return val; > +} > + > +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; > + > + /* > + * a maximum reset cycle time of 56 ms was measured. > + * we round it up to 100 ms > + */ > + for (i = 0; i < 100; i++) { > + val = gpiod_get_value(hx711_data->gpiod_dout); > + if (!val) > + break; > + /* sleep at least 1 ms */ > + msleep(1); > + } > + if (val) > + return -EIO; > + > + return 0; > +} > + > +static int hx711_reset(struct hx711_data *hx711_data) > +{ > + int ret; > + int val = gpiod_get_value(hx711_data->gpiod_dout); > + > + if (val) { > + /* > + * an examination with the oszilloscope indicated oscilloscope > + * 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); > + > + ret = hx711_wait_for_ready(hx711_data); > + if (ret) > + return ret; > + /* > + * after a reset the gain is 128 so we do a dummy read > + * to set the gain for the next read > + */ > + ret = hx711_read(hx711_data); > + if (ret < 0) > + return ret; > + > + /* > + * after a dummy read we need to wait vor readiness > + * for not mixing gain pulses with the clock > + */ > + ret = hx711_wait_for_ready(hx711_data); > + if (ret) > + return ret; > + } > + > + 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_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); > + int ret; > + > + switch (mask) { > + case IIO_CHAN_INFO_RAW: > + mutex_lock(&hx711_data->lock); > + > + /* > + * hx711_reset() must be called from here > + * because it could be calling hx711_read() by itself > + */ > + if (hx711_reset(hx711_data)) { No unlock in this error path. > + dev_err(hx711_data->dev, "reset failed!"); > + return -EIO; > + } > + > + ret = hx711_set_gain_for_channel(hx711_data, chan->channel); > + if (ret < 0) { > + mutex_unlock(&hx711_data->lock); > + return ret; > + } > + > + *val = hx711_read(hx711_data); > + > + 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); > + Looking feels overly paranoid here as we are only accessing locally stored data. Still it's not actively doing any harm... > + *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 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 struct attribute_group hx711_attribute_group = { > + .attrs = hx711_attributes, > +}; > + > +static const struct iio_info hx711_iio_info = { > + .driver_module = THIS_MODULE, > + .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), > + }, > + { > + .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), > + }, > +}; > + > +static int hx711_probe(struct platform_device *pdev) > +{ > + struct device *dev = &pdev->dev; > + 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) { > + regulator_disable(hx711_data->reg_avdd); > + return ret; > + } > + /* 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; > + > + platform_set_drvdata(pdev, indio_dev); > + > + indio_dev->name = "hx711"; > + indio_dev->dev.parent = &pdev->dev; > + 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_device_register(indio_dev); > + if (ret < 0) { > + dev_err(dev, "Couldn't register the device\n"); > + 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); > + > + 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@xxxxxxxxxxxxx>"); > +MODULE_DESCRIPTION("HX711 bitbanging driver - ADC for weight cells"); > +MODULE_LICENSE("GPL"); > +MODULE_ALIAS("platform:hx711-gpio"); > + > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html