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_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_read_raw(struct iio_dev *indio_dev,
const struct iio_chan_spec *chan,
int *val, int *val2, long mask)
{
struct hx711_data *hx711_data = iio_priv(indio_dev);
int ret;
switch (mask) {
case IIO_CHAN_INFO_RAW:
mutex_lock(&hx711_data->lock);
/*
* hx711_reset() must be called from here
* because it could be calling hx711_read() by itself
*/
if (hx711_reset(hx711_data)) {
mutex_unlock(&hx711_data->lock);
dev_err(hx711_data->dev, "reset failed!");
return -EIO;
}
ret = hx711_set_gain_for_channel(hx711_data, chan->channel);
if (ret < 0) {
mutex_unlock(&hx711_data->lock);
return ret;
}
*val = hx711_read(hx711_data);
mutex_unlock(&hx711_data->lock);
if (*val < 0)
return *val;
return IIO_VAL_INT;
case IIO_CHAN_INFO_SCALE:
*val = 0;
mutex_lock(&hx711_data->lock);
*val2 = hx711_get_gain_to_scale(hx711_data->gain_set);
mutex_unlock(&hx711_data->lock);
return IIO_VAL_INT_PLUS_NANO;
default:
return -EINVAL;
}
}
static int hx711_reset(struct hx711_data *hx711_data)
{
int ret;
int val = gpiod_get_value(hx711_data->gpiod_dout);
if (val) {
/*
* an examination with the oszilloscope indicated
* that the first value read after the reset is not stable
* if we reset too short;
* the shorter the reset cycle
* the less reliable the first value after reset is;
* there were no problems encountered with a value
* of 10 ms or higher
*/
gpiod_set_value(hx711_data->gpiod_pd_sck, 1);
msleep(10);
gpiod_set_value(hx711_data->gpiod_pd_sck, 0);
ret = hx711_wait_for_ready(hx711_data);
if (ret)
return ret;
/*
* after a reset the gain is 128 so we do a dummy read
* to set the gain for the next read
*/
ret = hx711_read(hx711_data);
if (ret < 0)
return ret;
/*
* after a dummy read we need to wait vor readiness
* for not mixing gain pulses with the clock
*/
ret = hx711_wait_for_ready(hx711_data);
if (ret)
return ret;
}
return val;
}
int main()
{
struct hx711_driver_t hx711;
float weight_a_128;
float weight_a_64;
float weight_b_32;
int res;
sys_start();
/* Initialize the driver. */
std_printf(OSTR("Initializing the HX711 driver... "));
res = hx711_init(&hx711,
&pin_d2_dev,
&pin_d3_dev,
SCALE,
OFFSET);
if (res == 0) {
std_printf(OSTR("done.\r\n"));
} else {
std_printf(OSTR("failed with %d.\r\n"), res);
return (res);
}
/* Start the driver. */
std_printf(OSTR("Starting the HX711 driver... "));
res = hx711_start(&hx711);
if (res == 0) {
std_printf(OSTR("done.\r\n"));
} else {
std_printf(OSTR("failed with %d.\r\n"), res);
return (res);
}
/* Continiously read samples from the device and print them. */
while (1) {
res = hx711_read(&hx711, &weight_a_128, hx711_channel_gain_a_128_t);
if (res != 0) {
std_printf(OSTR("Read 128 failed with %d.\r\n"), res);
}
res = hx711_read(&hx711, &weight_a_64, hx711_channel_gain_a_64_t);
if (res != 0) {
std_printf(OSTR("Read 64 failed with %d.\r\n"), res);
}
res = hx711_read(&hx711, &weight_b_32, hx711_channel_gain_b_32_t);
if (res != 0) {
std_printf(OSTR("Read 32 failed with %d.\r\n"), res);
}
/* Print the samples. */
std_printf(OSTR("Weight channel A gain 128: %f\r\n"
"Weight channel A gain 64: %f\r\n"
"Weight channel B gain 32: %f\r\n"
"\r\n"),
weight_a_128,
weight_a_64,
weight_b_32);
}
return (0);
}