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Date: Sat, 17 Dec 2016 00:53:55 -0800
From: Matt Ranostay <matt.ranostay@...sulko.com>
To: Andreas Klinger <ak@...klinger.de>
Cc: devicetree@...r.kernel.org, linux-iio@...r.kernel.org,
linux-kernel@...r.kernel.org, robh+dt@...nel.org,
pawel.moll@....com, mark.rutland@....com,
ijc+devicetree@...lion.org.uk, galak@...eaurora.org,
jic23@...nel.org, knaack.h@....de, lars@...afoo.de,
pmeerw@...erw.net
Subject: Re: [PATCH 2/2] iio: adc: hx711: Add IIO driver for AVIA HX711
On Tue, Dec 13, 2016 at 10:02 AM, Andreas Klinger <ak@...klinger.de> wrote:
> This is the IIO driver for AVIA HX711 ADC which ist mostly used in weighting
> cells.
First off cool that this is finally getting a driver... I'll have to
get the SparkFun breakout and really cheap scale to test :).
>
> The protocol is quite simple and using GPIO's:
> One GPIO is used as clock (SCK) while another GPIO is read (DOUT)
>
> Signed-off-by: Andreas Klinger <ak@...klinger.de>
> ---
> drivers/iio/adc/Kconfig | 13 +++
> drivers/iio/adc/Makefile | 1 +
> drivers/iio/adc/hx711.c | 269 +++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 283 insertions(+)
> create mode 100644 drivers/iio/adc/hx711.c
>
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 932de1f9d1e7..7902b50fcf32 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -205,6 +205,19 @@ 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 GPIO's, one for setting the clock and the other
> + one for getting the data
> +
> + 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..cbc89e467985
> --- /dev/null
> +++ b/drivers/iio/adc/hx711.c
> @@ -0,0 +1,269 @@
> +/*
> + * HX711: analog to digital converter for weight sensor module
> + *
> + * Copyright (c) Andreas Klinger <ak@...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/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;
> + dev_t devt;
> + struct gpio_desc *gpiod_sck;
> + struct gpio_desc *gpiod_dout;
> + int gain_pulse;
> + struct mutex lock;
> +};
> +
> +static void hx711_reset(struct hx711_data *hx711_data)
> +{
> + int val;
> + int i;
> +
> + val = gpiod_get_value(hx711_data->gpiod_dout);
could move the val assignment here to the initialization don't think
it will hit 80 chars
> + if (val) {
move "int i" here to avoid compiler initialization warnings
> + dev_warn(hx711_data->dev, "RESET-HX711\n");
> +
> + gpiod_set_value(hx711_data->gpiod_sck, 1);
> + udelay(80);
IIRC this chip has quite a bit of latency thresholds, can't use
usleep_range? Single core embedded systems could have an issue with
continuous polling.
> + 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);
> + }
> + }
> +}
> +
> +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 unsigned int hx711_read(struct hx711_data *hx711_data)
> +{
> + int i;
> + int ret;
> + int wert = 0;
> +
> + hx711_reset(hx711_data);
> +
> + for (i = 0; i < 24; i++) {
> + wert <<= 1;
> + ret = hx711_cycle(hx711_data);
> + if (ret)
> + wert++;
> + }
> +
> + wert ^= 0x800000;
> +
> + for (i = 0; i < hx711_data->gain_pulse; i++)
> + ret = hx711_cycle(hx711_data);
What is ret used for here?
> +
> + return wert;
> +}
> +
> +
> +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);
> + int ret;
> +
> + switch (mask) {
> + case IIO_CHAN_INFO_RAW:
> + switch (chan->type) {
> + case IIO_VOLTAGE:
> + mutex_lock(&hx711_data->lock);
> + *val = (int)hx711_read(hx711_data);
> + mutex_unlock(&hx711_data->lock);
> + ret = IIO_VAL_INT;
> + break;
> + default:
> + return -EINVAL;
> + }
> + return ret;
> + default:
> + return -EINVAL;
> + }
> +
> + return ret;
> +}
> +
> +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,
> + .channel = 0,
> + .info_mask_separate =
> + BIT(IIO_CHAN_INFO_RAW),
> + .scan_type = {
> + .sign = 'u',
> + .realbits = 24,
> + .storagebits = 32,
> + .shift = 0,
> + }
> + },
> +};
> +
> +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)) {
> + ret = PTR_ERR(hx711_data->gpiod_sck);
> + goto err;
> + }
> +
> + hx711_data->gpiod_dout = devm_gpiod_get(dev, "dout", GPIOD_OUT_HIGH);
> + if (IS_ERR(hx711_data->gpiod_dout)) {
> + ret = PTR_ERR(hx711_data->gpiod_dout);
> + goto err;
> + }
> +
> + ret = of_property_read_u32 (node, "gain", &ival);
> + if (!ret) {
> + switch (ival) {
> + case 32:
> + hx711_data->gain_pulse = HX711_GAIN_32;
> + break;
> + case 64:
> + hx711_data->gain_pulse = HX711_GAIN_64;
> + break;
> + case 128:
> + hx711_data->gain_pulse = HX711_GAIN_128;
> + break;
> + default:
> + hx711_data->gain_pulse = HX711_GAIN_128;
> + }
> + } else
> + 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);
> + goto err;
> + }
> +
> + ret = gpiod_direction_output(hx711_data->gpiod_sck, 0);
> + if (ret < 0) {
> + dev_err(hx711_data->dev, "gpiod_direction_output: %d\n", ret);
> + goto err;
> + }
> +
> + 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);
> +
> + dev_err(hx711_data->dev, "initialized\n");
> +
> + return devm_iio_device_register(dev, iio);
> +
> +err:
> + return ret;
> +}
> +
> +
> +static int hx711_suspend(struct device *dev)
> +{
> + return 0;
> +}
> +
> +static int hx711_resume(struct device *dev)
> +{
> + return 0;
> +}
> +
> +static SIMPLE_DEV_PM_OPS(hx711_pm_ops, hx711_suspend, hx711_resume);
> +
> +
> +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",
> + .pm = &hx711_pm_ops,
> + .of_match_table = of_hx711_match,
> + },
> +};
> +
> +module_platform_driver(hx711_driver);
> +
> +MODULE_AUTHOR("Andreas Klinger <ak@...klinger.de>");
> +MODULE_DESCRIPTION("HX711 bitbanging driver - ADC for weight cells");
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS("platform:hx711-gpio");
> +
> --
> 2.1.4
>
> --
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