diff options
Diffstat (limited to 'drivers/iio/adc/hx711.c')
| -rw-r--r-- | drivers/iio/adc/hx711.c | 644 |
1 files changed, 644 insertions, 0 deletions
diff --git a/drivers/iio/adc/hx711.c b/drivers/iio/adc/hx711.c new file mode 100644 index 000000000..0dc487dd1 --- /dev/null +++ b/drivers/iio/adc/hx711.c @@ -0,0 +1,644 @@ +/* + * 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/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 + +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 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 + */ + val = hx711_wait_for_ready(hx711_data); + } + + 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->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_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"); + |