linux/drivers/iio/adc/hx711.c

533 lines
12 KiB
C

/*
* HX711: analog to digital converter for weight sensor module
*
* Copyright (c) 2016 Andreas Klinger <ak@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/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 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);
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
* 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)) {
mutex_unlock(&hx711_data->lock);
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);
*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 const 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@it-klinger.de>");
MODULE_DESCRIPTION("HX711 bitbanging driver - ADC for weight cells");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:hx711-gpio");