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/*
* Copyright (c) 2016 Intel Corporation
*
* Licensed 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.
*/
#include <adc.h>
#include <device.h>
#include <math.h>
#include <sensor.h>
#include <zephyr.h>
#define SYS_LOG_DOMAIN "GROVE_TEMPERATURE_SENSOR"
#define SYS_LOG_LEVEL CONFIG_SYS_LOG_GROVE_LEVEL
#include <misc/sys_log.h>
/* thermistor Nominal B-Constant */
#if defined(CONFIG_GROVE_TEMPERATURE_SENSOR_V1_0)
#define B_CONST 3975
#elif defined(CONFIG_GROVE_TEMPERATURE_SENSOR_V1_X)
#define B_CONST 4250
#endif
struct gts_data {
struct device *adc;
struct adc_seq_entry sample;
struct adc_seq_table adc_table;
uint8_t adc_buffer[4];
};
static int gts_sample_fetch(struct device *dev, enum sensor_channel chan)
{
struct gts_data *drv_data = dev->driver_data;
return adc_read(drv_data->adc, &drv_data->adc_table);
}
static int gts_channel_get(struct device *dev,
enum sensor_channel chan,
struct sensor_value *val)
{
struct gts_data *drv_data = dev->driver_data;
uint16_t analog_val;
/* rescale sample from 12bit (Zephyr) to 10bit (Grove) */
analog_val = ((uint16_t)drv_data->adc_buffer[1] << 8) |
drv_data->adc_buffer[0];
analog_val = analog_val >> 2;
/*
* The formula for converting the analog value to degrees Celisus
* is taken from the sensor reference page:
* http://www.seeedstudio.com/wiki/Grove_-_Temperature_Sensor
*/
val->type = SENSOR_VALUE_TYPE_DOUBLE;
val->dval = 1 / (log(1023.0 / analog_val - 1.0) / B_CONST +
1 / 298.15) - 273.15;
return 0;
}
static const struct sensor_driver_api gts_api = {
.sample_fetch = >s_sample_fetch,
.channel_get = >s_channel_get,
};
static int gts_init(struct device *dev)
{
struct gts_data *drv_data = dev->driver_data;
drv_data->adc = device_get_binding(
CONFIG_GROVE_TEMPERATURE_SENSOR_ADC_DEV_NAME);
if (drv_data->adc == NULL) {
SYS_LOG_ERR("Failed to get ADC device.");
return -EINVAL;
}
drv_data->sample.sampling_delay = 12;
drv_data->sample.channel_id =
CONFIG_GROVE_TEMPERATURE_SENSOR_ADC_CHANNEL;
drv_data->sample.buffer = drv_data->adc_buffer;
drv_data->sample.buffer_length = 4;
drv_data->adc_table.entries = &drv_data->sample;
drv_data->adc_table.num_entries = 1;
adc_enable(drv_data->adc);
dev->driver_api = >s_api;
return 0;
}
struct gts_data gts_data;
DEVICE_INIT(gts_dev, CONFIG_GROVE_TEMPERATURE_SENSOR_NAME, >s_init, >s_data,
NULL, SECONDARY, CONFIG_SENSOR_INIT_PRIORITY);
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