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ADC¶

Overview¶

API Reference¶

group adc_interface

ADC driver APIs.

Defines

ADC_ACQ_TIME_MICROSECONDS¶: Acquisition time is expressed in microseconds.

ADC_ACQ_TIME_NANOSECONDS¶: Acquisition time is expressed in nanoseconds.

ADC_ACQ_TIME_TICKS¶: Acquisition time is expressed in ADC ticks.

ADC_ACQ_TIME(unit, value)¶: Macro for composing the acquisition time value in given units.

ADC_ACQ_TIME_DEFAULT¶: Value indicating that the default acquisition time should be used.

ADC_ACQ_TIME_UNIT(time)¶

ADC_ACQ_TIME_VALUE(time)¶

Typedefs

typedef enum adc_action (*adc_sequence_callback)(struct device *dev, const struct adc_sequence *sequence, u16_t sampling_index)¶

Type definition of the optional callback function to be called after a requested sampling is done.

Return

Action to be performed by the driver. See adc_action.

Parameters

dev: Pointer to the device structure for the driver instance.
sequence: Pointer to the sequence structure that triggered the sampling.
sampling_index: Index (0-65535) of the sampling done.

typedef int (*adc_api_channel_setup)(struct device *dev, const struct adc_channel_cfg *channel_cfg)¶: Type definition of ADC API function for configuring a channel. See adc_channel_setup() for argument descriptions.

typedef int (*adc_api_read)(struct device *dev, const struct adc_sequence *sequence)¶: Type definition of ADC API function for setting a read request. See adc_read() for argument descriptions.

Enums

enum adc_gain¶

ADC channel gain factors.

Values:

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.

enum adc_reference¶

ADC references.

Values:

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.

enum adc_action¶

Action to be performed after a sampling is done.

Values:

ADC_ACTION_CONTINUE = 0¶: The sequence should be continued normally.

ADC_ACTION_REPEAT¶: 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_FINISH¶: The sequence should be finished immediately.

Functions

int adc_gain_invert(enum adc_gain gain, s32_t *value)¶

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.

Parameters

gain: the gain used to amplify the input signal.
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.

Return Value

0: if the gain was successfully reversed
-EINVAL: if the gain could not be interpreted

static int adc_raw_to_millivolts(s32_t ref_mv, enum adc_gain gain, u8_t resolution, s32_t *valp)¶

Convert a raw ADC value to millivolts.

This function performs the necessary conversion to transform a raw ADC measurement to a voltage in millivolts.

Parameters

ref_mv: the reference voltage used for the measurement, in millivolts. This may be from adc_ref_internal() or a known external reference.
gain: the ADC gain configuration used to sample the input
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.
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.

Return Value

0: on successful conversion
-EINVAL: if the gain is not reversible

int adc_channel_setup(struct device *dev, const struct adc_channel_cfg *channel_cfg)¶

Configure an ADC channel.

It is required to call this function and configure each channel before it is selected for a read request.

Parameters

dev: Pointer to the device structure for the driver instance.
channel_cfg: Channel configuration.

Return Value

0: On success.
-EINVAL: If a parameter with an invalid value has been provided.

int adc_read(struct device *dev, const struct adc_sequence *sequence)¶

Set a read request.

If invoked from user mode, any sequence struct options for callback must be NULL.

Parameters

dev: Pointer to the device structure for the driver instance.
sequence: Structure specifying requested sequence of samplings.

Return Value

0: On success.
-EINVAL: If a parameter with an invalid value has been provided.
-ENOMEM: If the provided buffer is to small to hold the results of all requested samplings.
-ENOTSUP: If the requested mode of operation is not supported.
-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.

static u16_t adc_ref_internal(struct device *dev)¶

Get the internal reference voltage.

Returns the voltage corresponding to ADC_REF_INTERNAL, measured in millivolts.

Return: a positive value is the reference voltage value. Returns zero if reference voltage information is not available.

struct adc_channel_cfg¶: #include <adc.h>
Structure for specifying the configuration of an ADC channel.

struct adc_sequence_options¶: #include <adc.h>
Structure defining additional options for an ADC sampling sequence.

struct adc_sequence¶: #include <adc.h>
Structure defining an ADC sampling sequence.

struct adc_driver_api¶

#include <adc.h>

ADC driver API.

This is the mandatory API any ADC driver needs to expose.