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iio: adc: hx711: Add IIO driver for AVIA HX711
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@it-klinger.de> Signed-off-by: Jonathan Cameron <jic23@kernel.org>
This commit is contained in:
Andreas Klinger
Jonathan Cameron
parent
ff1293f677
commit
c3b2fdd0ea
@ -247,6 +247,25 @@ config HI8435
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This driver can also be built as a module. If so, the module will be
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called hi8435.
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config HX711
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tristate "AVIA HX711 ADC for weight cells"
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depends on GPIOLIB
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help
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If you say yes here you get support for AVIA HX711 ADC which is used
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for weigh cells
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This driver uses two GPIOs, one acts as the clock and controls the
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channel selection and gain, the other one is used for the measurement
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data
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Currently the raw value is read from the chip and delivered.
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To get an actual weight one needs to subtract the
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zero offset and multiply by a scale factor.
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This should be done in userspace.
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This driver can also be built as a module. If so, the module will be
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called hx711.
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config INA2XX_ADC
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tristate "Texas Instruments INA2xx Power Monitors IIO driver"
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depends on I2C && !SENSORS_INA2XX
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@ -25,6 +25,7 @@ obj-$(CONFIG_ENVELOPE_DETECTOR) += envelope-detector.o
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obj-$(CONFIG_EXYNOS_ADC) += exynos_adc.o
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obj-$(CONFIG_FSL_MX25_ADC) += fsl-imx25-gcq.o
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obj-$(CONFIG_HI8435) += hi8435.o
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obj-$(CONFIG_HX711) += hx711.o
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obj-$(CONFIG_IMX7D_ADC) += imx7d_adc.o
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obj-$(CONFIG_INA2XX_ADC) += ina2xx-adc.o
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obj-$(CONFIG_LP8788_ADC) += lp8788_adc.o
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532
drivers/iio/adc/hx711.c
Normal file
532
drivers/iio/adc/hx711.c
Normal file
@ -0,0 +1,532 @@
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/*
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* HX711: analog to digital converter for weight sensor module
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*
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* Copyright (c) 2016 Andreas Klinger <ak@it-klinger.de>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#include <linux/err.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/of.h>
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#include <linux/platform_device.h>
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#include <linux/property.h>
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#include <linux/slab.h>
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#include <linux/sched.h>
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#include <linux/delay.h>
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#include <linux/iio/iio.h>
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#include <linux/iio/sysfs.h>
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#include <linux/gpio/consumer.h>
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#include <linux/regulator/consumer.h>
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/* gain to pulse and scale conversion */
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#define HX711_GAIN_MAX 3
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struct hx711_gain_to_scale {
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int gain;
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int gain_pulse;
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int scale;
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int channel;
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};
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/*
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* .scale depends on AVDD which in turn is known as soon as the regulator
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* is available
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* therefore we set .scale in hx711_probe()
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*
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* channel A in documentation is channel 0 in source code
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* channel B in documentation is channel 1 in source code
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*/
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static struct hx711_gain_to_scale hx711_gain_to_scale[HX711_GAIN_MAX] = {
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{ 128, 1, 0, 0 },
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{ 32, 2, 0, 1 },
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{ 64, 3, 0, 0 }
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};
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static int hx711_get_gain_to_pulse(int gain)
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{
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int i;
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for (i = 0; i < HX711_GAIN_MAX; i++)
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if (hx711_gain_to_scale[i].gain == gain)
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return hx711_gain_to_scale[i].gain_pulse;
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return 1;
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}
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static int hx711_get_gain_to_scale(int gain)
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{
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int i;
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for (i = 0; i < HX711_GAIN_MAX; i++)
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if (hx711_gain_to_scale[i].gain == gain)
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return hx711_gain_to_scale[i].scale;
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return 0;
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}
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static int hx711_get_scale_to_gain(int scale)
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{
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int i;
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for (i = 0; i < HX711_GAIN_MAX; i++)
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if (hx711_gain_to_scale[i].scale == scale)
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return hx711_gain_to_scale[i].gain;
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return -EINVAL;
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}
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struct hx711_data {
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struct device *dev;
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struct gpio_desc *gpiod_pd_sck;
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struct gpio_desc *gpiod_dout;
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struct regulator *reg_avdd;
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int gain_set; /* gain set on device */
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int gain_chan_a; /* gain for channel A */
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struct mutex lock;
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};
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static int hx711_cycle(struct hx711_data *hx711_data)
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{
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int val;
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/*
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* if preempted for more then 60us while PD_SCK is high:
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* hx711 is going in reset
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* ==> measuring is false
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*/
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preempt_disable();
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gpiod_set_value(hx711_data->gpiod_pd_sck, 1);
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val = gpiod_get_value(hx711_data->gpiod_dout);
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/*
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* here we are not waiting for 0.2 us as suggested by the datasheet,
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* because the oscilloscope showed in a test scenario
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* at least 1.15 us for PD_SCK high (T3 in datasheet)
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* and 0.56 us for PD_SCK low on TI Sitara with 800 MHz
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*/
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gpiod_set_value(hx711_data->gpiod_pd_sck, 0);
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preempt_enable();
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return val;
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}
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static int hx711_read(struct hx711_data *hx711_data)
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{
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int i, ret;
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int value = 0;
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int val = gpiod_get_value(hx711_data->gpiod_dout);
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/* we double check if it's really down */
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if (val)
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return -EIO;
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for (i = 0; i < 24; i++) {
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value <<= 1;
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ret = hx711_cycle(hx711_data);
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if (ret)
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value++;
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}
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value ^= 0x800000;
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for (i = 0; i < hx711_get_gain_to_pulse(hx711_data->gain_set); i++)
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hx711_cycle(hx711_data);
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return value;
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}
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static int hx711_wait_for_ready(struct hx711_data *hx711_data)
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{
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int i, val;
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/*
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* a maximum reset cycle time of 56 ms was measured.
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* we round it up to 100 ms
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*/
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for (i = 0; i < 100; i++) {
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val = gpiod_get_value(hx711_data->gpiod_dout);
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if (!val)
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break;
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/* sleep at least 1 ms */
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msleep(1);
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}
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if (val)
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return -EIO;
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return 0;
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}
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static int hx711_reset(struct hx711_data *hx711_data)
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{
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int ret;
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int val = gpiod_get_value(hx711_data->gpiod_dout);
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if (val) {
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/*
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* an examination with the oszilloscope indicated
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* that the first value read after the reset is not stable
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* if we reset too short;
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* the shorter the reset cycle
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* the less reliable the first value after reset is;
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* there were no problems encountered with a value
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* of 10 ms or higher
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*/
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gpiod_set_value(hx711_data->gpiod_pd_sck, 1);
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msleep(10);
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gpiod_set_value(hx711_data->gpiod_pd_sck, 0);
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ret = hx711_wait_for_ready(hx711_data);
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if (ret)
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return ret;
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/*
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* after a reset the gain is 128 so we do a dummy read
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* to set the gain for the next read
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*/
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ret = hx711_read(hx711_data);
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if (ret < 0)
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return ret;
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/*
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* after a dummy read we need to wait vor readiness
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* for not mixing gain pulses with the clock
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*/
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ret = hx711_wait_for_ready(hx711_data);
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if (ret)
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return ret;
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}
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return val;
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}
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static int hx711_set_gain_for_channel(struct hx711_data *hx711_data, int chan)
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{
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int ret;
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if (chan == 0) {
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if (hx711_data->gain_set == 32) {
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hx711_data->gain_set = hx711_data->gain_chan_a;
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ret = hx711_read(hx711_data);
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if (ret < 0)
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return ret;
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ret = hx711_wait_for_ready(hx711_data);
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if (ret)
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return ret;
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}
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} else {
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if (hx711_data->gain_set != 32) {
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hx711_data->gain_set = 32;
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ret = hx711_read(hx711_data);
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if (ret < 0)
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return ret;
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ret = hx711_wait_for_ready(hx711_data);
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if (ret)
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return ret;
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}
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}
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return 0;
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}
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static int hx711_read_raw(struct iio_dev *indio_dev,
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const struct iio_chan_spec *chan,
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int *val, int *val2, long mask)
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{
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struct hx711_data *hx711_data = iio_priv(indio_dev);
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int ret;
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switch (mask) {
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case IIO_CHAN_INFO_RAW:
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mutex_lock(&hx711_data->lock);
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/*
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* hx711_reset() must be called from here
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* because it could be calling hx711_read() by itself
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*/
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if (hx711_reset(hx711_data)) {
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mutex_unlock(&hx711_data->lock);
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dev_err(hx711_data->dev, "reset failed!");
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return -EIO;
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}
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ret = hx711_set_gain_for_channel(hx711_data, chan->channel);
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if (ret < 0) {
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mutex_unlock(&hx711_data->lock);
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return ret;
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}
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*val = hx711_read(hx711_data);
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mutex_unlock(&hx711_data->lock);
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if (*val < 0)
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return *val;
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return IIO_VAL_INT;
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case IIO_CHAN_INFO_SCALE:
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*val = 0;
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mutex_lock(&hx711_data->lock);
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*val2 = hx711_get_gain_to_scale(hx711_data->gain_set);
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mutex_unlock(&hx711_data->lock);
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return IIO_VAL_INT_PLUS_NANO;
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default:
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return -EINVAL;
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}
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}
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static int hx711_write_raw(struct iio_dev *indio_dev,
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struct iio_chan_spec const *chan,
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int val,
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int val2,
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long mask)
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{
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struct hx711_data *hx711_data = iio_priv(indio_dev);
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int ret;
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int gain;
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switch (mask) {
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case IIO_CHAN_INFO_SCALE:
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/*
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* a scale greater than 1 mV per LSB is not possible
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* with the HX711, therefore val must be 0
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*/
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if (val != 0)
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return -EINVAL;
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mutex_lock(&hx711_data->lock);
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gain = hx711_get_scale_to_gain(val2);
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if (gain < 0) {
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mutex_unlock(&hx711_data->lock);
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return gain;
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}
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if (gain != hx711_data->gain_set) {
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hx711_data->gain_set = gain;
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if (gain != 32)
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hx711_data->gain_chan_a = gain;
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ret = hx711_read(hx711_data);
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if (ret < 0) {
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mutex_unlock(&hx711_data->lock);
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return ret;
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}
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}
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mutex_unlock(&hx711_data->lock);
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return 0;
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default:
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return -EINVAL;
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}
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return 0;
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}
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static int hx711_write_raw_get_fmt(struct iio_dev *indio_dev,
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struct iio_chan_spec const *chan,
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long mask)
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{
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return IIO_VAL_INT_PLUS_NANO;
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}
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static ssize_t hx711_scale_available_show(struct device *dev,
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struct device_attribute *attr,
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char *buf)
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{
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struct iio_dev_attr *iio_attr = to_iio_dev_attr(attr);
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int channel = iio_attr->address;
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int i, len = 0;
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for (i = 0; i < HX711_GAIN_MAX; i++)
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if (hx711_gain_to_scale[i].channel == channel)
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len += sprintf(buf + len, "0.%09d ",
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hx711_gain_to_scale[i].scale);
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len += sprintf(buf + len, "\n");
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return len;
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}
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static IIO_DEVICE_ATTR(in_voltage0_scale_available, S_IRUGO,
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hx711_scale_available_show, NULL, 0);
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static IIO_DEVICE_ATTR(in_voltage1_scale_available, S_IRUGO,
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hx711_scale_available_show, NULL, 1);
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static struct attribute *hx711_attributes[] = {
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&iio_dev_attr_in_voltage0_scale_available.dev_attr.attr,
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&iio_dev_attr_in_voltage1_scale_available.dev_attr.attr,
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NULL,
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};
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static struct attribute_group hx711_attribute_group = {
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.attrs = hx711_attributes,
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};
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static const struct iio_info hx711_iio_info = {
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.driver_module = THIS_MODULE,
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.read_raw = hx711_read_raw,
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.write_raw = hx711_write_raw,
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.write_raw_get_fmt = hx711_write_raw_get_fmt,
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.attrs = &hx711_attribute_group,
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};
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static const struct iio_chan_spec hx711_chan_spec[] = {
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{
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.type = IIO_VOLTAGE,
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.channel = 0,
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.indexed = 1,
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.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
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.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
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},
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{
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.type = IIO_VOLTAGE,
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.channel = 1,
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.indexed = 1,
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.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
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.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
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},
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};
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static int hx711_probe(struct platform_device *pdev)
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{
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struct device *dev = &pdev->dev;
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struct hx711_data *hx711_data;
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struct iio_dev *indio_dev;
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int ret;
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int i;
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indio_dev = devm_iio_device_alloc(dev, sizeof(struct hx711_data));
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if (!indio_dev) {
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dev_err(dev, "failed to allocate IIO device\n");
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return -ENOMEM;
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}
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hx711_data = iio_priv(indio_dev);
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hx711_data->dev = dev;
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mutex_init(&hx711_data->lock);
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/*
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* PD_SCK stands for power down and serial clock input of HX711
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* in the driver it is an output
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*/
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hx711_data->gpiod_pd_sck = devm_gpiod_get(dev, "sck", GPIOD_OUT_LOW);
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if (IS_ERR(hx711_data->gpiod_pd_sck)) {
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dev_err(dev, "failed to get sck-gpiod: err=%ld\n",
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PTR_ERR(hx711_data->gpiod_pd_sck));
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return PTR_ERR(hx711_data->gpiod_pd_sck);
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}
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/*
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* DOUT stands for serial data output of HX711
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* for the driver it is an input
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*/
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hx711_data->gpiod_dout = devm_gpiod_get(dev, "dout", GPIOD_IN);
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if (IS_ERR(hx711_data->gpiod_dout)) {
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dev_err(dev, "failed to get dout-gpiod: err=%ld\n",
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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@it-klinger.de>");
|
||||
MODULE_DESCRIPTION("HX711 bitbanging driver - ADC for weight cells");
|
||||
MODULE_LICENSE("GPL");
|
||||
MODULE_ALIAS("platform:hx711-gpio");
|
||||
|
||||
Loading…
Reference in New Issue
Block a user