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drivers/analog/hx711.c: Add driver for hx711 adc

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Signed-off-by: Michał Łyszczek <michal.lyszczek@bofc.pl>
This commit is contained in:
Michał Łyszczek 2024-02-25 09:15:36 +01:00 committed by Alan Carvalho de Assis
parent b634798bd6
commit 84a2cab886
7 changed files with 1439 additions and 0 deletions
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220
Documentation/components/drivers/character/hx711.rst Normal file
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@ -0,0 +1,220 @@
=============================
HX711 ADC DESIGNED FOR SCALES
=============================
Driver contributed by Michał Łyszczek.
HX711 is a 24bit ADC (Analog Digital Converter) designed for weight scales.
This chip can be very slow. With internal oscillator and RATE pin pulled
down, it outputs only 10 samples per second. To not hog down CPU, driver
uses interrupt to detect when chip is ready. This will make read(2) blocking,
but system can do whatever it needs before chip is ready. Because of that
driver does not fully follow ADC API, but rather standard character device
(read only).
Values from tensometer can be easily read from shell with ``cat`` command
.. code-block::
cat /dev/hxx711_0
Altough it may be better to dump values with example ``hx711`` program,
since ``cat`` will just read until the end of time, and if ctrl+c is
not working, it will steal shell forever.
-------
reading
-------
Reading is done by calling standard, posix, read(2) function. Only one value
can be returned with single call to read(2). But an averaging function can
be enabled, so that driver will read N samples, average them, and then will
return single averaged value.
This function accepts two types of buffer.
If buffer is of size ``sizeof(int32_t)`` a int32 value will be stored in
a buffer. If buffer size of bigger than ``sizeof(int32_t)`` function will
store string representation of values in passed buffer.
Simple code to read and print value may look like this
.. code-block:: C
int fd;
fd = open("/dev/hx711_0", O_RDONLY);
for (; ; )
{
int32_t value;
value = read(fd, &value, sizeof(value));
printf("Read: %"PRIi32"\n", value);
}
-----
ioctl
-----
Since this chip (and driver) is designed for weight scale, kernel driver
can provide some processing to make life easier for userspace code. These
functions are implemented via ioctl(2) commands. In practice, non of these
can be used, but if you just open driver and read it, you will get raw
values from hx711 chip, which you will have to process yourself. If your
needs are more standard, it's better to use kernel processing.
HX711_SET_AVERAGE
-----------------
.. code-block:: C
unsigned average = 5;
ioctl(fd, HX711_SET_AVERAGE, average);
Driver will read this number of samples from hx711 and will return average
value of them all. To avoid corrupted data due to integer overflow, max
average value that can be set is 225. If you need to average more values
you will need to write your own code for that.
HX711_SET_CHANNEL
-----------------
.. code-block:: C
char channel = 'a';
ioctl(fd, HX711_SET_CHANNEL, channel);
HX711 has 2 channels, A and B, which can be swapped as necessary. Driver
automatically performs dummy read, so that next call to read(2) will return
value from new channel. When you switch to channel 'B', driver automatically
changes gain to 32 (the only possible value). Going back to 'A' will set
gain to 128.
HX711_SET_GAIN
--------------
.. code-block:: C
unsigned char gain = 128;
ioctl(fd, HX711_SET_GAIN, gain);
Set gain. Channel 'A' supports gain "128" and "64". Channel 'B' has only
one gain option - 32.
HX711_SET_VAL_PER_UNIT
----------------------
.. code-block:: C
int val_per_unit = 813;
ioctl(fd, HX711_SET_VAL_PER_UNIT, val_per_unit);
Driver can perform calculations so that you can read physical values like
grams, ounce or pounds, or your own artificial unit. You just need to specify
what value from tensometer coresponds to one unit.
Say you have tensometer that has max value of 1'000'000. Value 100'000 means
1kg and sensor is fully linear. If you want to get readings in kg, you would
set ``val_per_unit`` to 100'000. If you wanted output in grams, it would be
value of 100. To have tenths of grams precision, you would set it to 10.
Driver does not care about unit, you just pick one and stick to it.
Note that driver can only return integers, so if you set it to return unit
of kg, you will only get 1, 2, 3kg... and you won't be able to sense 0.5kg
or 1.5kg. For that you would have to set value to 10'000, and driver would
return you values of 15 (for 1.5kg) or 0.5 (for 0.5kg).
HX711_TARE
----------
.. code-block:: C
float precision = 0.1;
ioctl(fd, HX711_TARE, &precision);
Every scale needs a tare function. Driver polls hx711 for some time, and if
it detects that scale is stable state, ioctl(2) will return with success,
and next read(2) call will take new tare value into consideration when
returning readings. Scale is assumed to be stable when several consecutive
readings are (min-max values) are within specified precition.
If ``HX711_SET_VAL_PER_UNIT`` was set prior to this, you can pass value
in your unit. If you configured driver to work with grams, you can set
this value to 0.1 (gram) or 5 (gram).
If driver cannot get stable reading within some time, it will return with
ETIME errno set.
Important note, make sure you have set correct sign before taring, or
else you will double your tare value instead of zeroing it!
HX711_SIGN
----------
.. code-block:: C
int sign = -1;
ioctl(fd, HX711_SIGN, &sign);
If values from drivers go lower when mass on scale goes higher you can swap
the sign. This may be necessary when tensometer was installed upside down.
---------------------
hx711 example program
---------------------
There is also companion program in Application Configuration ---> Examples
called ``HX711 driver example``. Main purpose of this is to show how to
use the driver, but it also is a very good tool for quickly debuging chip
from the shell, as it can dump readings and set all options.
.. code-block::
-h print this help message
-d<path> path to hx711 device, default: /dev/hx711_0
-t<prec> tares the scale with specified precision, might take few seconds to complete.
If you set value per unit, precision is in units, otherwise it's raw values.
If units are used, float can be passed like 0.1
-v<val> value read that coresponds to one unit. This value has to be
calibrated first before it's known
-s reverse sign, if values decreses when mass increases, pass this
-D dumps current device settings (like, average, channel, gain etc.)
-a<avg> set how many samples should be averaged before returning value,
values [1..225] are valid
-c<chan> set channel to read (either 'a' or 'b' is valid)
-g<gain> set adc gain, for channel 'a' 64 and 128 are valid,
for channel 'b', only 64 is valid
-r<num> read this number of samples before exiting, samples will be printed
on stdout as string, one sample per line
Set values are persistant, as in once set they are stored in driver and
will be applied during execution of this program.
If you specify only <-a|-c|-g|-v|-t> without -r, program will set new parameters
and exit. You can later call program again only with -r option to read
samples with previously set values. You can also pass all of them in one call
To test if you require CONFIG_ADC_HX711_ADD_DELAY option set, run as:
hx711 -a225 -r128
This will load hx711 chip long enough to show any possible errors due to
lack of added delay.
Program executes in order: set options, tare, dump, run, so if you specify all
options, new settings will be applied, then new settings will be printed
and at the end program will tare the scale and print samples
Examples:
Set hx711 settings for first chip and exit:
hx711 -a32 -ca -g64
Dump chip settings from different chip
hx711 -d/dev/hx711_2 -D
Read 10 samples with previously set hx711 settings
hx711 -r10
Change channel and read 32 samples (average setting won't change):
hx711 -cb -r32
Set value per unit, to get output in grams, and then tare with 10g precision
hx711 -v 813 -t 10

1
Documentation/components/drivers/character/index.rst
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@ -61,6 +61,7 @@ Character device drivers have these properties:
contactless.rst contactless.rst
crypto/index.rst crypto/index.rst
efuse.rst efuse.rst
hx711.rst
i2s.rst i2s.rst
input/index.rst input/index.rst
ipcc.rst ipcc.rst

4
drivers/analog/CMakeLists.txt
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@ -91,6 +91,10 @@ if(CONFIG_ADC)
if(CONFIG_ADC_LTC1867L) if(CONFIG_ADC_LTC1867L)
list(APPEND SRCS ltc1867l.c) list(APPEND SRCS ltc1867l.c)
endif() endif()
if(CONFIG_ADC_HX711)
list(APPEND SRCS hx711.c)
endif()
endif() endif()
if(CONFIG_LMP92001) if(CONFIG_LMP92001)

37
drivers/analog/Kconfig
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@ -192,6 +192,43 @@ endchoice
endif # ADC_MAX1161X endif # ADC_MAX1161X
config ADC_HX711
bool "Avia Semiconductor HX711 support"
default n
---help---
Enable driver to support Avia Semiconductor HX711 ADC
designed for weight scales.
Driver supports both 'a' and 'b' channels with 32, 64
and 128 gain.
Driver does not support continuous read and is not buffered.
Driver uses interrupts to not hog the CPU while waiting
for hx711 to be ready.
if ADC_HX711
config ADC_HA711_ADD_DELAY
bool "Add 1us delay between clock pulses"
default y if BOARD_LOOPSPERMSEC >= 15000
---help---
HX711 requires about 1us between clock pulses to work.
This is not an issue on slower chips, but faster chips
will most likely try to clock HX711 too fast, which
will result in data lose.
If this is enabled, code will insert 1us of delay to each
clock change. Enable this only if you get data lose, or
else you will just introduce unnecessary delay to your
program.
Best way to know if you need this, is to compile
HX711 demo program and run it. If there are no errors
reported during runtime, you can turn this of. If you
see communication errors, then you should enable this.
endif # ADC_HX711
endif # ADC endif # ADC
config COMP config COMP

4
drivers/analog/Make.defs
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@ -103,6 +103,10 @@ endif
ifeq ($(CONFIG_ADC_LTC1867L),y) ifeq ($(CONFIG_ADC_LTC1867L),y)
CSRCS += ltc1867l.c CSRCS += ltc1867l.c
endif endif
ifeq ($(CONFIG_ADC_HX711),y)
CSRCS += hx711.c
endif
endif endif
ifeq ($(CONFIG_LMP92001),y) ifeq ($(CONFIG_LMP92001),y)

961
drivers/analog/hx711.c Normal file
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@ -0,0 +1,961 @@
/****************************************************************************
* drivers/analog/hx711.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <nuttx/compiler.h>
#include <nuttx/kmalloc.h>
#include <nuttx/irq.h>
#include <sys/param.h>
#include <ctype.h>
#include <stdio.h>
#include <nuttx/analog/hx711.h>
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
#define DEVNAME_FMT "/dev/hx711_%d"
#define DEVNAME_FMTLEN (11 + 3 + 1)
/* hx711 is a 24 bit ADC, but in case they decide to do like a
* hx771s(uperb) with 32 bit resolution, here is easy to change def
*/
#define HX711_BITS_PER_READ 24
#define HX711_TARE_MAX_LOOP 64
#define HX711_TARE_NSAMPLES 5
/****************************************************************************
* Private Types
****************************************************************************/
struct hx711_dev_s
{
FAR struct hx711_lower_s *lower;
mutex_t excl;
sem_t hx711_ready;
int crefs;
int unlinked;
unsigned char minor;
int val_per_unit;
long tare;
unsigned char average;
unsigned char gain;
char channel;
signed char sign;
};
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
static int hx711_open(FAR struct file *filep);
static int hx711_close(FAR struct file *filep);
static int hx711_unlink(FAR struct inode *inode);
static int hx711_ioctl(FAR struct file *filep, int cmd, unsigned long arg);
static ssize_t hx711_read(FAR struct file *filep,
FAR char *buf, size_t buflen);
static int32_t hx711_single_read(FAR struct hx711_dev_s *dev);
/****************************************************************************
* Private Data
****************************************************************************/
static const struct file_operations g_hx711_fops =
{
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
.unlink = hx711_unlink,
#endif /* CONFIG_DISABLE_PSEUDOFS_OPERATIONS */
.open = hx711_open,
.close = hx711_close,
.read = hx711_read,
.ioctl = hx711_ioctl
};
/****************************************************************************
* Public Data
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: hx711_tare
*
* Description:
* Tares the scale. Function will read some number of samples and will
* check if these readings are stable (more or less the same within
* specified precision). If operation is a success, next call to read()
* will return value close to 0 (if no force is applied to tensometer).
*
* Input Parameters:
* dev - hx711 instance to tare
* precision - precision with which to tare the scale. If set to 100
* function will set new tare if min-max values read are
* less than 100
*
* Returned Value:
* OK - on success
* -EIO - no communication with the hx711
* -ETIME - scale was not stable for HX711_TARE_NSAMPLES loops
*
****************************************************************************/
static int hx711_tare(FAR struct hx711_dev_s *dev, float precision)
{
int32_t samples[HX711_TARE_NSAMPLES];
int i;
int j;
int min;
int max;
long tare;
int prec;
long taresave;
/* If value per unit is defined, we assume precision is specified
* in units, calculate raw value for precision
*/
prec = dev->val_per_unit > 0 ? precision * dev->val_per_unit : precision;
/* Save old tare value, which we will restore when we have an error */
taresave = dev->tare;
/* Reset tare value during taring */
dev->tare = 0;
for (i = 0; i != HX711_TARE_NSAMPLES; i++)
{
samples[i] = hx711_single_read(dev);
if (samples[i] == INT32_MIN)
{
dev->tare = taresave;
return -EIO;
}
}
for (i = 0; i != HX711_TARE_MAX_LOOP; i++)
{
/* Check if scale reading is stable */
min = INT_MAX;
max = INT_MIN;
for (j = 0; j != HX711_TARE_NSAMPLES; j++)
{
min = samples[j] < min ? samples[j] : min;
max = samples[j] > max ? samples[j] : max;
}
if (max - min <= prec)
{
/* Scale readings are stable within specified precision.
* Use average of these readings to set new tare value.
*/
for (tare = j = 0; j != HX711_TARE_NSAMPLES; j++)
{
tare += samples[j];
}
tare /= HX711_TARE_NSAMPLES;
dev->tare = tare;
return OK;
}
/* Reading is not yet stable, perform next read and check
* stability again
*/
samples[i % HX711_TARE_NSAMPLES] = hx711_single_read(dev);
if (samples[i % HX711_TARE_NSAMPLES] == INT32_MIN)
{
dev->tare = taresave;
return -EIO;
}
}
/* If we get here, we couldn't get stable readings within specified
* limit
*/
dev->tare = taresave;
return -ETIME;
}
/****************************************************************************
* Name: hx711_ioctl
*
* Description:
* Perform device specific operations.
*
* Input Parameters:
* filep - file on vfs associated with the driver.
* cmd - command to perform
* arg - argument for the cmd
*
* Returned Value:
* Returns OK on success or negated errno on failure.
*
****************************************************************************/
static int hx711_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
{
FAR struct hx711_dev_s *dev;
int ret;
dev = filep->f_inode->i_private;
/* Get exclusive access to the hx711 driver state */
ret = nxmutex_lock(&dev->excl);
if (ret < 0)
{
return ret;
}
ret = OK;
switch (cmd)
{
case HX711_SET_AVERAGE:
if (arg < 1 || arg > HX711_MAX_AVG_SAMPLES)
{
/* Averaging more than HX711_MAX_AVG_SAMPLES samples could
* overflow averaging variable leading to invalid reading.
*/
ret = -EINVAL;
break;
}
dev->average = arg;
break;
case HX711_SET_CHANNEL:
if (arg != 'a' || arg != 'b')
{
/* Only channel a or b are available */
ret = -EINVAL;
break;
}
dev->channel = arg;
if (dev->channel == 'b')
{
/* Only valid gain for channel b is 32, adjust */
dev->gain = 32;
}
if (dev->channel == 'a')
{
/* If we are switching from channel 'b', gain will be 32,
* which is invalid value for channel 'a'. If current gain
* is not valid for channel 'a', set default value of 128
*/
if (dev->gain != 128 && dev->gain != 64)
{
dev->gain = 128;
}
}
/* Channel setting will be applied after next read from hx711,
* we have to do one dummy read, so that user can immediately
* read from new channel
*/
if (hx711_single_read(dev) == INT32_MIN)
{
ret = -EIO;
}
break;
case HX711_SET_GAIN:
if (dev->channel == 'a' && (arg != 128 || arg != 64))
{
/* For channel 'a' only gain of value 128 and 64 are valid */
ret = -EINVAL;
break;
}
else if (dev->channel == 'b' && arg != 32)
{
/* For channel 'b' only gain of 32 is valid */
ret = -EINVAL;
break;
}
dev->gain = arg;
break;
case HX711_SET_VAL_PER_UNIT:
dev->val_per_unit = arg;
break;
case HX711_GET_AVERAGE:
{
unsigned *ptr = (unsigned *)((uintptr_t)arg);
if (ptr == NULL)
{
ret = -EINVAL;
break;
}
*ptr = dev->average;
break;
}
case HX711_GET_CHANNEL:
{
char *ptr = (char *)((uintptr_t)arg);
if (ptr == NULL)
{
ret = -EINVAL;
break;
}
*ptr = dev->channel;
break;
}
case HX711_GET_GAIN:
{
unsigned char *ptr = (unsigned char *)((uintptr_t)arg);
if (ptr == NULL)
{
ret = -EINVAL;
break;
}
*ptr = dev->gain;
break;
}
case HX711_GET_VAL_PER_UNIT:
{
unsigned *ptr = (unsigned *)((uintptr_t)arg);
if (ptr == NULL)
{
ret = -EINVAL;
break;
}
*ptr = dev->val_per_unit;
break;
}
case HX711_TARE:
{
float *precision = (float *)((uintptr_t)arg);
if (precision == NULL)
{
ret = -EINVAL;
break;
}
ret = hx711_tare(dev, *precision);
break;
}
case HX711_SET_SIGN:
{
int *sign = (int *)((uintptr_t)arg);
if (sign == NULL || (*sign != 1 && *sign != -1))
{
ret = EINVAL;
break;
}
dev->sign = *sign;
break;
}
default:
ret = EINVAL;
}
nxmutex_unlock(&dev->excl);
return ret;
}
/****************************************************************************
* Name: hx711_data_interrupt
*
* Description:
* Function is called when we are waiting for hx711 to be ready and once
* data line goes from HIGH to LOW state.
*
* Input Parameters:
* arg - hx711 device instance
*
****************************************************************************/
static int hx711_data_interrupt(int irq, FAR void *context, FAR void *arg)
{
UNUSED(irq);
UNUSED(context);
FAR struct hx711_dev_s *dev = arg;
nxsem_post(&dev->hx711_ready);
return 0;
}
/****************************************************************************
* Name: hx711_wait_ready
*
* Description:
* Waits for conversion to be ready to read.
*
* Input Parameters:
* dev - hx711 device instance
*
* Returned Value:
* Function returns OK when chip is ready for reading, or -EIO, which
* means there is problem communicating with the device.
*
****************************************************************************/
static int hx711_wait_ready(FAR struct hx711_dev_s *dev)
{
int ret;
struct timespec tp;
/* It is possible that there was no read() call for long enough
* that hx711 is already ready, if that is the case just quickly return
*/
if (dev->lower->data_read(dev->minor) == 0)
{
return OK;
}
/* Install data line interrupt, so we know when hx711 is ready.
* This can even be 100ms between sampling, and up to 500ms when
* hx711 goes out of low power mode
*/
if ((ret = dev->lower->data_irq(dev->minor, hx711_data_interrupt, dev)))
{
return ret;
}
/* During waiting for ready signal, clock should be low */
dev->lower->clock_set(dev->minor, 0);
clock_gettime(CLOCK_MONOTONIC, &tp);
tp.tv_sec += 1;
if ((ret = nxsem_timedwait(&dev->hx711_ready, &tp)))
{
/* Chip not ready for long time. This probably mean that the
* hx711 chip is not properly (if at all) connected.
*/
dev->lower->data_irq(dev->minor, NULL, NULL);
return -EIO;
}
/* hx711 is ready */
dev->lower->data_irq(dev->minor, NULL, NULL);
return OK;
}
/****************************************************************************
* Name: hx711_delay
*
* Description:
* hx711 datasheet specifies that time between clock changes should be
* between 0.2us and 50us, with typical value of 1us. On slow MCUs this
* is not a problem, as all operations between clocking take longer than
* that time, but on fast CHIP, clocking without delay will cause data
* lose.
*
****************************************************************************/
static void hx711_delay(void)
{
#ifdef CONFIG_ADC_HX711_ADD_DELAY
up_delay(1);
#endif
}
/****************************************************************************
* Name: hx711_single_read
*
* Description:
* Reads single, 24bit adc data from hx711. Function will perform
* conversion form 24bit 2's complement to 32bit 2's complement.
*
* Input Parameters:
* dev - hx711 instance to perform read from.
*
* Returned Value:
* Read value from hx711. Returned value is stored on 24 bits of
* int32_t type. If there was error during read, function will
* return INT32_MIN.
*
****************************************************************************/
static int32_t hx711_single_read(FAR struct hx711_dev_s *dev)
{
int32_t value;
int i;
int pulses;
int flags;
int ret;
/* Wait for conversion to be finished */
if ((ret = hx711_wait_ready(dev)))
{
/* Timeout while waiting for chip, assuming chip is not connected */
nxmutex_unlock(&dev->excl);
return INT32_MIN;
}
/* Even though we are clocking the hx711, we must perform whole readout
* without interruption. This is because, if we set clock pin to HIGH,
* hx711 will go into low power mode in 60us unless we set clock to LOW
* within that time.
*/
flags = enter_critical_section();
for (value = i = 0; i != HX711_BITS_PER_READ; i++)
{
dev->lower->clock_set(dev->minor, 1);
hx711_delay();
/* Data is sent MSB first */
value |= dev->lower->data_read(dev->minor);
value <<= 1;
dev->lower->clock_set(dev->minor, 0);
hx711_delay();
}
/* Next few clock pulses will determine type of next conversion
* hx711 will perform. We gotta do this in the same critical
* section block as read.
*
* 1 pulse - Channel A, Gain 128
* 2 pulses - Channel B, Gain 32
* 3 pulses - Channel A, Gain 64
*/
if (dev->channel == 'b')
{
/* Channel B has static gain of 32 */
pulses = 2;
}
else
{
/* channel A has 2 possible gains, either 128 or 64. */
pulses = dev->gain == 128 ? 1 : 3;
}
for (i = 0; i != pulses; i++)
{
dev->lower->clock_set(dev->minor, 1);
hx711_delay();
dev->lower->clock_set(dev->minor, 0);
hx711_delay();
}
leave_critical_section(flags);
/* Data is sent in standard 2's complement, but we just stored
* 24bit integer in a 32bit integer. For positives reading this
* makes no difference, but if we have just returned 24bit negative
* number in 32bit integer, we would end up with positive (and false)
* reading.
*
* If number is negative, convert it to 32bit negative.
*/
if (value & 0x800000)
{
value |= 0xff000000;
}
/* Apply tare value and sign at the end */
return dev->sign * (value + dev->tare);
}
/****************************************************************************
* Name: hx711_read
*
* Description:
* Performs read from the hx711 device. Only a single value can be read
* with single call, but when averaging is enabled, driver will read
* configured number of points and will return single, average value
* of them all.
*
* Input Parameters:
* filep - file on vfs associated with the driver.
* buf - pointer to 32bit integer where value will be stored.
* buflen - size of buf, must be equal to 4 (sizeof(int32_t))
*
* Returned Value:
* On success 4 is returned (sizeof(int32_t)), as in number of bytes
* copied to userspace. On failure, negated errno is returned.
*
****************************************************************************/
static ssize_t hx711_read(FAR struct file *filep,
FAR char *buf, size_t buflen)
{
FAR struct hx711_dev_s *dev;
int ret;
int32_t value; /* 24bit value from hx711 will be stored here */
int32_t average;
unsigned i;
value = 0;
dev = filep->f_inode->i_private;
if (buflen == 0)
{
return 0;
}
if (buflen < sizeof(int32_t))
{
return -EINVAL;
}
/* Get exclusive access to the hx711 driver state */
ret = nxmutex_lock(&dev->excl);
if (ret < 0)
{
return ret;
}
for (i = 1; i <= dev->average; i++)
{
value = hx711_single_read(dev);
if (value == INT32_MIN)
{
/* There was error while reading sample. */
nxmutex_unlock(&dev->excl);
return -EIO;
}
average = (average * (i - 1) + value) / i;
}
/* We are done with the device, so free mutex for next possible client */
nxmutex_unlock(&dev->excl);
/* If user specified value per unit, we convert raw data into units */
if (dev->val_per_unit > 0)
{
average /= dev->val_per_unit;
}
/* Copy data back to userspace and exit */
if (buflen == sizeof(int32_t))
{
/* int32 was passed, assuming binary operation from C code */
memcpy(buf, &average, sizeof(average));
return sizeof(int32_t);
}
else
{
/* Something else passed, assuming it's shell operation. If it's
* called from C, it's assumed user wants c-string.
*/
ret = snprintf(buf, buflen, "%"PRIi32"\n", average);
/* snprintf returns number of bytes written (or that would have
* been written) without null byte, but we return number of bytes
* written including that byte, hence +1.
*/
ret += 1;
/* If buflen is not big enough, snprintf() will return number
* of bytes that would have been written to buf if enough space
* had been available and not number of bytes actually written.
* We must return number of bytes actually written, so we take
* smaller value.
*/
return MIN(ret, (int)buflen);
}
}
/****************************************************************************
* Name: hx711_cleanup
*
* Description:
* Called when last user closed hx711 dsevice and that device is (or was)
* unlinked.
*
* Input Parameters:
* dev - hx711 device instance.
*
****************************************************************************/
static void hx711_cleanup(FAR struct hx711_dev_s *dev)
{
/* Put chip into sleep state by setting clock to HIGH */
dev->lower->clock_set(dev->minor, 1);
if (dev->lower->cleanup)
{
dev->lower->cleanup(dev->minor);
}
nxmutex_destroy(&dev->excl);
nxsem_destroy(&dev->hx711_ready);
kmm_free(dev);
}
/****************************************************************************
* Name: hx711_open
*
* Description:
* Open driver for use by userspace application.
*
* Input Parameters:
* filep - pointer to a file structure to open
*
* Returned Value:
* OK on success, or negated errno on failure
*
****************************************************************************/
static int hx711_open(FAR struct file *filep)
{
FAR struct hx711_dev_s *dev;
int ret;
dev = filep->f_inode->i_private;
/* Get exclusive access to the hx711 driver state */
ret = nxmutex_lock(&dev->excl);
if (ret < 0)
{
return ret;
}
/* Increment the count of open references on the driver */
dev->crefs++;
DEBUGASSERT(dev->crefs > 0);
nxmutex_unlock(&dev->excl);
return OK;
}
/****************************************************************************
* Name: hx711_close
*
* Description:
* Closes the driver device. If this is last reference and file has been
* unlinked, we will also free resources allocated by ipcc_register()
*
* Input Parameters:
* filep - pointer to a file structure to close.
*
* Returned Value:
* OK on success, or negated errno on failure.
*
****************************************************************************/
static int hx711_close(FAR struct file *filep)
{
FAR struct hx711_dev_s *dev;
int ret;
dev = filep->f_inode->i_private;
/* Get exclusive access to the hx711 driver state */
ret = nxmutex_lock(&dev->excl);
if (ret < 0)
{
return ret;
}
/* Decrement the count of open references on the driver */
DEBUGASSERT(dev->crefs > 0);
dev->crefs--;
if (dev->crefs <= 0 && dev->unlinked)
{
/* If count ref is zero and file has been unlinked, it
* means nobody uses the driver and seems like nobody
* wants to use it anymore, so free up resources. This
* also means we are last holders of excl mutex, which
* will be destroyed in cleanup function, so we don't
* have to unlock it here.
*/
hx711_cleanup(dev);
return OK;
}
nxmutex_unlock(&dev->excl);
return OK;
}
/****************************************************************************
* Name: hx711_unlink
*
* Description:
* Action to take upon file unlinking. Function will free resources if
* noone is using the driver when unlinking occured. If driver is still
* in use, it will be marked as unlinked and resource freeing will take
* place in hx711_close() function instead, once last reference is closed.
*
* Input Parameters:
* inode - driver inode that is being unlinked.
*
* Returned Value:
* OK on successfull close, or negated errno on failure.
*
****************************************************************************/
static int hx711_unlink(FAR struct inode *inode)
{
FAR struct hx711_dev_s *dev;
int ret;
dev = inode->i_private;
/* Get exclusive access to the hx711 driver state */
ret = nxmutex_lock(&dev->excl);
if (ret < 0)
{
return ret;
}
/* Is anyone still using the driver? */
if (dev->crefs <= 0)
{
/* No, we are free to free resources */
hx711_cleanup(dev);
return OK;
}
/* Yes, someone is still using the driver, just mark file
* as unlinked and free resources in hx711_close() once last
* reference is closed.
*/
dev->unlinked = true;
nxmutex_unlock(&dev->excl);
return OK;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: hx711_register
*
* Description:
* Register new hx711 device in /dev/hx711_%d. Multiple hx711 can be
* supported by providing different minor number. When driver calls
* platform specific function, minor number is passed back, so platform
* can know which hx711 is manipulated.
*
* Input Parameters:
* minor - unique number identifying hx711 chip.
* lower - provided by platform code to manipulate hx711 with platform
* dependant functions>
*
* Returned Value:
* OK on success, or negated errno on failure
*
****************************************************************************/
int hx711_register(unsigned char minor, FAR struct hx711_lower_s *lower)
{
FAR struct hx711_dev_s *dev;
char devname[DEVNAME_FMTLEN];
int ret;
dev = kmm_zalloc(sizeof(*dev));
if (dev == NULL)
{
return -ENOMEM;
}
snprintf(devname, DEVNAME_FMTLEN, DEVNAME_FMT, minor);
ret = register_driver(devname, &g_hx711_fops, 0666, dev);
if (ret)
{
kmm_free(dev);
return ret;
}
dev->channel = 'a';
dev->gain = 128;
dev->lower = lower;
dev->average = 1;
dev->sign = 1;
nxmutex_init(&dev->excl);
nxsem_init(&dev->hx711_ready, 0, 0);
/* Put chip into working state by setting clock to LOW */
dev->lower->clock_set(dev->minor, 0);
return OK;
}

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include/nuttx/analog/hx711.h Normal file
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/****************************************************************************
* include/nuttx/analog/hx711.h
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <nuttx/compiler.h>
#include <nuttx/irq.h>
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
#define HX711_MAX_AVG_SAMPLES 225
/* ioctl requests ***********************************************************/
/* Set how many samples to read from hx711 to get a single averaged value.
* Minimum value is 1. To prevent possible integer overflow, maximum value
* is HX711_MAX_AVG_SAMPLES.
*/
#define HX711_SET_AVERAGE 0
/* Set channel to use for next read() operation. Channels 'a' and 'b'
* are available. Specify channel as 'a' character (0x61 hex)
*/
#define HX711_SET_CHANNEL 1
/* Set gain to use for next read() operation. Channel 'b' only supports
* gain of 32, and channel 'a' supports gain 128 and 64
*/
#define HX711_SET_GAIN 2
/* Set what value coresponds to 1 unit. Takes integer.
* If set to 0 (default) driver will return raw readings from
* hx711 instead of calculated units.
*/
#define HX711_SET_VAL_PER_UNIT 3
/* Depending on tensometer position, value will go higher or lower
* (into negative values) when mass increases. If your sign does
* not match, it can be changed by calling this.
* 1 - no sign change (default)
* -1 - sign will be changed
*/
#define HX711_SET_SIGN 4
/* ioctl get functions */
/* Get current average, pass pointer to unsigned int type */
#define HX711_GET_AVERAGE 100
/* Get current channel, pass pointer to single char */
#define HX711_GET_CHANNEL 101
/* Get current gain, pass pointer to single unsignedchar */
#define HX711_GET_GAIN 102
/* Get current value per unit */
#define HX711_GET_VAL_PER_UNIT 103
/* Tare the scale. Accepts int value with desired precision.
* If HX711_VAL_PER_UNIT was set earlier, you should pass value
* in units, otherwise you need to pass raw value as read from hx711.
* Takes pointer to a float value.
*/
#define HX711_TARE 200
/****************************************************************************
* Public Types
****************************************************************************/
/* hx711 exposes 2 pins for communication. One is for data reading, and
* second one is clock signal. This is similar to i2c but hx711 uses custom
* protocol that is not compatible with i2c in any way.
*
* Platform code should provide these functions to manipulate these GPIOs
*/
struct hx711_lower_s
{
/**************************************************************************
* Name: clock_set
*
* Description:
* Sets underlying GPIO pin according to val.
*
* Input Parameters:
* val - set GPIO pin high (1) or low (0)
* minor - hx711 device being manipulated
*
* Returned Value:
* OK on success, or negated errno on failure
*
**************************************************************************/
CODE int (*clock_set)(unsigned char minor, int val);
/**************************************************************************
* Name: data_read
*
* Description:
* Reads current value of data GPIO pin.
*
* Input Parameters:
* minor - hx711 device being manipulated
*
* Returned Value:
* For success, return 0 when GPIO is low, 1 when GPIO is high
* or negated errno on failure.
*
**************************************************************************/
CODE int (*data_read)(unsigned char minor);
/**************************************************************************
* Name: cleanup
*
* Description:
* This function is called when last instance of minor is closed and
* unlinked from fs so that hx711 minor instance is no longer available.
* Platform should free all resources it allocated to register the
* device.
*
* This function does not have to be set, if there is nothing to clean.
*
* Input Parameters:
* minor - hx711 instance being destroyed
*
**************************************************************************/
CODE void (*cleanup)(unsigned char minor);
/**************************************************************************
* Name: data_irq
*
* Description:
* Setup (or tear down when handler is NULL) interrupt when data line
* goes from HIGH to LOW state (falling edge).
*
* hx711 is slow, on internal oscillator and RATE=0 it takes 100ms to
* sample a single reading. To avoid hogging CPU polling for data to
* go down, driver will install interrupt handler before reading.
* Once interrupt is received, driver will disable the handler.
*
* Input Parameters:
* minor - hx711 device being manipulated
* handler - function interrupt should call
* arg - private data for handler, should be passed to handler
*
* Returned Value:
* On successfull interrupt initialization 0 should be returned,
* when there was failure initializing interrupt -1 shall be returned.
*
**************************************************************************/
CODE int (*data_irq)(unsigned char minor, xcpt_t handler, void *arg);
};
/****************************************************************************
* Public Functions Prototypes
****************************************************************************/
/****************************************************************************
* Name: hx711_register
*
* Description:
* Register new hx711 device in /dev/hx711_%d. Multiple hx711 can be
* supported by providing different minor number. When driver calls
* platform specific function, minor number is passed back, so platform
* can know which hx711 is manipulated.
*
* Input Parameters:
* minor - unique number identifying hx711 chip.
* lower - provided by platform code to manipulate hx711 with platform
* dependant functions>
*
* Returned Value:
* OK on success, or negated errno on failure
*
****************************************************************************/
int hx711_register(unsigned char minor, FAR struct hx711_lower_s *lower);