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 <ak@xxxxxxxxxxxxx> --- 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 <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/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 <ak@xxxxxxxxxxxxx>"); +MODULE_DESCRIPTION("HX711 bitbanging driver - ADC for weight cells"); +MODULE_LICENSE("GPL"); +MODULE_ALIAS("platform:hx711-gpio"); + -- 2.1.4 -- 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