645 lines
15 KiB
C
645 lines
15 KiB
C
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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/iio/buffer.h>
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#include <linux/iio/trigger_consumer.h>
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#include <linux/iio/triggered_buffer.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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* triggered buffer
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* 2x32-bit channel + 64-bit timestamp
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*/
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u32 buffer[4];
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/*
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* delay after a rising edge on SCK until the data is ready DOUT
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* this is dependent on the hx711 where the datasheet tells a
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* maximum value of 100 ns
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* but also on potential parasitic capacities on the wiring
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*/
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u32 data_ready_delay_ns;
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u32 clock_frequency;
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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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unsigned long flags;
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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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local_irq_save(flags);
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gpiod_set_value(hx711_data->gpiod_pd_sck, 1);
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/*
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* wait until DOUT is ready
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* it turned out that parasitic capacities are extending the time
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* until DOUT has reached it's value
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*/
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ndelay(hx711_data->data_ready_delay_ns);
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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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local_irq_restore(flags);
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/*
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* make it a square wave for addressing cases with capacitance on
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* PC_SCK
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*/
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ndelay(hx711_data->data_ready_delay_ns);
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/* sample as late as possible */
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return gpiod_get_value(hx711_data->gpiod_dout);
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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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* in some rare cases the reset takes quite a long time
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* especially when the channel is changed.
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* Allow up to one second for it
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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 10 ms */
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msleep(10);
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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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val = hx711_wait_for_ready(hx711_data);
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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_reset_read(struct hx711_data *hx711_data, int chan)
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{
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int ret;
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int val;
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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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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);
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if (ret < 0)
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return ret;
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val = hx711_read(hx711_data);
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return val;
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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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switch (mask) {
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case IIO_CHAN_INFO_RAW:
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mutex_lock(&hx711_data->lock);
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*val = hx711_reset_read(hx711_data, chan->channel);
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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 irqreturn_t hx711_trigger(int irq, void *p)
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{
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struct iio_poll_func *pf = p;
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struct iio_dev *indio_dev = pf->indio_dev;
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struct hx711_data *hx711_data = iio_priv(indio_dev);
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int i, j = 0;
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mutex_lock(&hx711_data->lock);
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memset(hx711_data->buffer, 0, sizeof(hx711_data->buffer));
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for (i = 0; i < indio_dev->masklength; i++) {
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if (!test_bit(i, indio_dev->active_scan_mask))
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||
|
|
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");
|
||
|
|
|