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/**
* @file
* @brief ADC public API header file.
*/
/*
* Copyright (c) 2018 Nordic Semiconductor ASA
* Copyright (c) 2015 Intel Corporation
*
* SPDX-License-Identifier: Apache-2.0
*/
#ifndef ZEPHYR_INCLUDE_DRIVERS_ADC_H_
#define ZEPHYR_INCLUDE_DRIVERS_ADC_H_
#include <device.h>
#ifdef __cplusplus
extern "C" {
#endif
/**
* @brief ADC driver APIs
* @defgroup adc_interface ADC driver APIs
* @ingroup io_interfaces
* @{
*/
/** @brief ADC channel gain factors. */
enum adc_gain {
ADC_GAIN_1_6, /**< x 1/6. */
ADC_GAIN_1_5, /**< x 1/5. */
ADC_GAIN_1_4, /**< x 1/4. */
ADC_GAIN_1_3, /**< x 1/3. */
ADC_GAIN_1_2, /**< x 1/2. */
ADC_GAIN_2_3, /**< x 2/3. */
ADC_GAIN_1, /**< x 1. */
ADC_GAIN_2, /**< x 2. */
ADC_GAIN_3, /**< x 3. */
ADC_GAIN_4, /**< x 4. */
ADC_GAIN_8, /**< x 8. */
ADC_GAIN_16, /**< x 16. */
ADC_GAIN_32, /**< x 32. */
ADC_GAIN_64, /**< x 64. */
ADC_GAIN_128, /**< x 128. */
};
/**
* @brief Invert the application of gain to a measurement value.
*
* For example, if the gain passed in is ADC_GAIN_1_6 and the
* referenced value is 10, the value after the function returns is 60.
*
* @param gain the gain used to amplify the input signal.
*
* @param value a pointer to a value that initially has the effect of
* the applied gain but has that effect removed when this function
* successfully returns. If the gain cannot be reversed the value
* remains unchanged.
*
* @retval 0 if the gain was successfully reversed
* @retval -EINVAL if the gain could not be interpreted
*/
int adc_gain_invert(enum adc_gain gain,
int32_t *value);
/** @brief ADC references. */
enum adc_reference {
ADC_REF_VDD_1, /**< VDD. */
ADC_REF_VDD_1_2, /**< VDD/2. */
ADC_REF_VDD_1_3, /**< VDD/3. */
ADC_REF_VDD_1_4, /**< VDD/4. */
ADC_REF_INTERNAL, /**< Internal. */
ADC_REF_EXTERNAL0, /**< External, input 0. */
ADC_REF_EXTERNAL1, /**< External, input 1. */
};
/** Acquisition time is expressed in microseconds. */
#define ADC_ACQ_TIME_MICROSECONDS (1u)
/** Acquisition time is expressed in nanoseconds. */
#define ADC_ACQ_TIME_NANOSECONDS (2u)
/** Acquisition time is expressed in ADC ticks. */
#define ADC_ACQ_TIME_TICKS (3u)
/** Macro for composing the acquisition time value in given units. */
#define ADC_ACQ_TIME(unit, value) (((unit) << 14) | ((value) & BIT_MASK(14)))
/** Value indicating that the default acquisition time should be used. */
#define ADC_ACQ_TIME_DEFAULT 0
#define ADC_ACQ_TIME_UNIT(time) (((time) >> 14) & BIT_MASK(2))
#define ADC_ACQ_TIME_VALUE(time) ((time) & BIT_MASK(14))
/**
* @brief Structure for specifying the configuration of an ADC channel.
*/
struct adc_channel_cfg {
/** Gain selection. */
enum adc_gain gain;
/** Reference selection. */
enum adc_reference reference;
/**
* Acquisition time.
* Use the ADC_ACQ_TIME macro to compose the value for this field or
* pass ADC_ACQ_TIME_DEFAULT to use the default setting for a given
* hardware (e.g. when the hardware does not allow to configure the
* acquisition time).
* Particular drivers do not necessarily support all the possible units.
* Value range is 0-16383 for a given unit.
*/
uint16_t acquisition_time;
/**
* Channel identifier.
* This value primarily identifies the channel within the ADC API - when
* a read request is done, the corresponding bit in the "channels" field
* of the "adc_sequence" structure must be set to include this channel
* in the sampling.
* For hardware that does not allow selection of analog inputs for given
* channels, but rather have dedicated ones, this value also selects the
* physical ADC input to be used in the sampling. Otherwise, when it is
* needed to explicitly select an analog input for the channel, or two
* inputs when the channel is a differential one, the selection is done
* in "input_positive" and "input_negative" fields.
* Particular drivers indicate which one of the above two cases they
* support by selecting or not a special hidden Kconfig option named
* ADC_CONFIGURABLE_INPUTS. If this option is not selected, the macro
* CONFIG_ADC_CONFIGURABLE_INPUTS is not defined and consequently the
* mentioned two fields are not present in this structure.
* While this API allows identifiers from range 0-31, particular drivers
* may support only a limited number of channel identifiers (dependent
* on the underlying hardware capabilities or configured via a dedicated
* Kconfig option).
*/
uint8_t channel_id : 5;
/** Channel type: single-ended or differential. */
uint8_t differential : 1;
#ifdef CONFIG_ADC_CONFIGURABLE_INPUTS
/**
* Positive ADC input.
* This is a driver dependent value that identifies an ADC input to be
* associated with the channel.
*/
uint8_t input_positive;
/**
* Negative ADC input (used only for differential channels).
* This is a driver dependent value that identifies an ADC input to be
* associated with the channel.
*/
uint8_t input_negative;
#endif /* CONFIG_ADC_CONFIGURABLE_INPUTS */
};
/**
* @brief Convert a raw ADC value to millivolts.
*
* This function performs the necessary conversion to transform a raw
* ADC measurement to a voltage in millivolts.
*
* @param ref_mv the reference voltage used for the measurement, in
* millivolts. This may be from adc_ref_internal() or a known
* external reference.
*
* @param gain the ADC gain configuration used to sample the input
*
* @param resolution the number of bits in the absolute value of the
* sample. For differential sampling this may be one less than the
* resolution in struct adc_sequence.
*
* @param valp pointer to the raw measurement value on input, and the
* corresponding millivolt value on successful conversion. If
* conversion fails the stored value is left unchanged.
*
* @retval 0 on successful conversion
* @retval -EINVAL if the gain is not reversible
*/
static inline int adc_raw_to_millivolts(int32_t ref_mv,
enum adc_gain gain,
uint8_t resolution,
int32_t *valp)
{
int32_t adc_mv = *valp * ref_mv;
int ret = adc_gain_invert(gain, &adc_mv);
if (ret == 0) {
*valp = (adc_mv >> resolution);
}
return ret;
}
/* Forward declaration of the adc_sequence structure. */
struct adc_sequence;
/**
* @brief Action to be performed after a sampling is done.
*/
enum adc_action {
/** The sequence should be continued normally. */
ADC_ACTION_CONTINUE = 0,
/**
* The sampling should be repeated. New samples or sample should be
* read from the ADC and written in the same place as the recent ones.
*/
ADC_ACTION_REPEAT,
/** The sequence should be finished immediately. */
ADC_ACTION_FINISH,
};
/**
* @brief Type definition of the optional callback function to be called after
* a requested sampling is done.
*
* @param dev Pointer to the device structure for the driver
* instance.
* @param sequence Pointer to the sequence structure that triggered the
* sampling.
* @param sampling_index Index (0-65535) of the sampling done.
*
* @returns Action to be performed by the driver. See @ref adc_action.
*/
typedef enum adc_action (*adc_sequence_callback)(const struct device *dev,
const struct adc_sequence *sequence,
uint16_t sampling_index);
/**
* @brief Structure defining additional options for an ADC sampling sequence.
*/
struct adc_sequence_options {
/**
* Interval between consecutive samplings (in microseconds), 0 means
* sample as fast as possible, without involving any timer.
* The accuracy of this interval is dependent on the implementation of
* a given driver. The default routine that handles the intervals uses
* a kernel timer for this purpose, thus, it has the accuracy of the
* kernel's system clock. Particular drivers may use some dedicated
* hardware timers and achieve a better precision.
*/
uint32_t interval_us;
/**
* Callback function to be called after each sampling is done.
* Optional - set to NULL if it is not needed.
*/
adc_sequence_callback callback;
/**
* Number of extra samplings to perform (the total number of samplings
* is 1 + extra_samplings).
*/
uint16_t extra_samplings;
};
/**
* @brief Structure defining an ADC sampling sequence.
*/
struct adc_sequence {
/**
* Pointer to a structure defining additional options for the sequence.
* If NULL, the sequence consists of a single sampling.
*/
const struct adc_sequence_options *options;
/**
* Bit-mask indicating the channels to be included in each sampling
* of this sequence.
* All selected channels must be configured with adc_channel_setup()
* before they are used in a sequence.
*/
uint32_t channels;
/**
* Pointer to a buffer where the samples are to be written. Samples
* from subsequent samplings are written sequentially in the buffer.
* The number of samples written for each sampling is determined by
* the number of channels selected in the "channels" field.
* The buffer must be of an appropriate size, taking into account
* the number of selected channels and the ADC resolution used,
* as well as the number of samplings contained in the sequence.
*/
void *buffer;
/**
* Specifies the actual size of the buffer pointed by the "buffer"
* field (in bytes). The driver must ensure that samples are not
* written beyond the limit and it must return an error if the buffer
* turns out to be not large enough to hold all the requested samples.
*/
size_t buffer_size;
/**
* ADC resolution.
* For single-ended channels the sample values are from range:
* 0 .. 2^resolution - 1,
* for differential ones:
* - 2^(resolution-1) .. 2^(resolution-1) - 1.
*/
uint8_t resolution;
/**
* Oversampling setting.
* Each sample is averaged from 2^oversampling conversion results.
* This feature may be unsupported by a given ADC hardware, or in
* a specific mode (e.g. when sampling multiple channels).
*/
uint8_t oversampling;
/**
* Perform calibration before the reading is taken if requested.
*
* The impact of channel configuration on the calibration
* process is specific to the underlying hardware. ADC
* implementations that do not support calibration should
* ignore this flag.
*/
bool calibrate;
};
/**
* @brief Type definition of ADC API function for configuring a channel.
* See adc_channel_setup() for argument descriptions.
*/
typedef int (*adc_api_channel_setup)(const struct device *dev,
const struct adc_channel_cfg *channel_cfg);
/**
* @brief Type definition of ADC API function for setting a read request.
* See adc_read() for argument descriptions.
*/
typedef int (*adc_api_read)(const struct device *dev,
const struct adc_sequence *sequence);
#ifdef CONFIG_ADC_ASYNC
/**
* @brief Type definition of ADC API function for setting an asynchronous
* read request.
* See adc_read_async() for argument descriptions.
*/
typedef int (*adc_api_read_async)(const struct device *dev,
const struct adc_sequence *sequence,
struct k_poll_signal *async);
#endif
/**
* @brief ADC driver API
*
* This is the mandatory API any ADC driver needs to expose.
*/
__subsystem struct adc_driver_api {
adc_api_channel_setup channel_setup;
adc_api_read read;
#ifdef CONFIG_ADC_ASYNC
adc_api_read_async read_async;
#endif
uint16_t ref_internal; /* mV */
};
/**
* @brief Configure an ADC channel.
*
* It is required to call this function and configure each channel before it is
* selected for a read request.
*
* @param dev Pointer to the device structure for the driver instance.
* @param channel_cfg Channel configuration.
*
* @retval 0 On success.
* @retval -EINVAL If a parameter with an invalid value has been provided.
*/
__syscall int adc_channel_setup(const struct device *dev,
const struct adc_channel_cfg *channel_cfg);
static inline int z_impl_adc_channel_setup(const struct device *dev,
const struct adc_channel_cfg *channel_cfg)
{
const struct adc_driver_api *api =
(const struct adc_driver_api *)dev->api;
return api->channel_setup(dev, channel_cfg);
}
/**
* @brief Set a read request.
*
* @param dev Pointer to the device structure for the driver instance.
* @param sequence Structure specifying requested sequence of samplings.
*
* If invoked from user mode, any sequence struct options for callback must
* be NULL.
*
* @retval 0 On success.
* @retval -EINVAL If a parameter with an invalid value has been provided.
* @retval -ENOMEM If the provided buffer is to small to hold the results
* of all requested samplings.
* @retval -ENOTSUP If the requested mode of operation is not supported.
* @retval -EBUSY If another sampling was triggered while the previous one
* was still in progress. This may occur only when samplings
* are done with intervals, and it indicates that the selected
* interval was too small. All requested samples are written
* in the buffer, but at least some of them were taken with
* an extra delay compared to what was scheduled.
*/
__syscall int adc_read(const struct device *dev,
const struct adc_sequence *sequence);
static inline int z_impl_adc_read(const struct device *dev,
const struct adc_sequence *sequence)
{
const struct adc_driver_api *api =
(const struct adc_driver_api *)dev->api;
return api->read(dev, sequence);
}
#ifdef CONFIG_ADC_ASYNC
/**
* @brief Set an asynchronous read request.
*
* If invoked from user mode, any sequence struct options for callback must
* be NULL.
*
* @param dev Pointer to the device structure for the driver instance.
* @param sequence Structure specifying requested sequence of samplings.
* @param async Pointer to a valid and ready to be signaled struct
* k_poll_signal. (Note: if NULL this function will not notify
* the end of the transaction, and whether it went successfully
* or not).
*
* @returns 0 on success, negative error code otherwise.
*
*/
__syscall int adc_read_async(const struct device *dev,
const struct adc_sequence *sequence,
struct k_poll_signal *async);
static inline int z_impl_adc_read_async(const struct device *dev,
const struct adc_sequence *sequence,
struct k_poll_signal *async)
{
const struct adc_driver_api *api =
(const struct adc_driver_api *)dev->api;
return api->read_async(dev, sequence, async);
}
#endif /* CONFIG_ADC_ASYNC */
/**
* @brief Get the internal reference voltage.
*
* Returns the voltage corresponding to @ref ADC_REF_INTERNAL,
* measured in millivolts.
*
* @return a positive value is the reference voltage value. Returns
* zero if reference voltage information is not available.
*/
static inline uint16_t adc_ref_internal(const struct device *dev)
{
const struct adc_driver_api *api =
(const struct adc_driver_api *)dev->api;
return api->ref_internal;
}
/**
* @}
*/
#ifdef __cplusplus
}
#endif
#include <syscalls/adc.h>
#endif /* ZEPHYR_INCLUDE_DRIVERS_ADC_H_ */