ADC driver

group nrfx_adc

Analog-to-Digital Converter (ADC) peripheral driver.

Defines

NRFX_ADC_DEFAULT_CHANNEL(analog_input)

ADC channel default configuration.

This configuration sets up ADC channel with the following options:

  • 10 bits resolution

  • full scale input

  • reference voltage: 1.2 V

  • external reference input disabled

Parameters:

  • analog_input – [in] Analog input.

NRFX_ADC_DEFAULT_CONFIG

ADC default configuration.

Typedefs

typedef struct nrfx_adc_channel_s nrfx_adc_channel_t

Forward declaration of the nrfx_adc_channel_t type.

typedef void (*nrfx_adc_event_handler_t)(nrfx_adc_evt_t const *p_event)

User event handler prototype.

This function is called when the requested number of samples has been processed.

Param p_event:

Event.

Enums

enum nrfx_adc_evt_type_t

Driver event types.

Values:

enumerator NRFX_ADC_EVT_DONE

Event generated when the buffer is filled with samples.

enumerator NRFX_ADC_EVT_SAMPLE

Event generated when the requested channel is sampled.

Functions

nrfx_err_t nrfx_adc_init(nrfx_adc_config_t const *p_config, nrfx_adc_event_handler_t event_handler)

Function for initializing the ADC.

If a valid event handler is provided, the driver is initialized in non-blocking mode. If event_handler is NULL, the driver works in blocking mode.

Parameters:

  • p_config – [in] Pointer to the structure with the initial configuration.

  • event_handler – [in] Event handler provided by the user.

Return values:

  • NRFX_SUCCESS – Initialization was successful.

  • NRFX_ERROR_INVALID_STATE – The driver is already initialized.

void nrfx_adc_uninit(void)

Function for uninitializing the ADC.

This function stops all ongoing conversions and disables all channels.

void nrfx_adc_channel_enable(nrfx_adc_channel_t *const p_channel)

Function for enabling an ADC channel.

This function configures and enables the channel. When nrfx_adc_buffer_convert is called, all channels that have been enabled with this function are sampled.

This function can be called only when there is no conversion in progress (the ADC is not busy).

Note

The channel instance variable p_channel is used by the driver as an item in a list. Therefore, it cannot be an automatic variable that is located on the stack.

Parameters:

  • p_channel – [in] Pointer to the channel instance.

void nrfx_adc_channel_disable(nrfx_adc_channel_t *const p_channel)

Function for disabling an ADC channel.

This function can be called only when there is no conversion in progress (the ADC is not busy).

Parameters:

  • p_channel – Pointer to the channel instance.

void nrfx_adc_all_channels_disable(void)

Function for disabling all ADC channels.

This function can be called only when there is no conversion in progress (the ADC is not busy).

void nrfx_adc_sample(void)

Function for starting ADC sampling.

This function triggers single ADC sampling. If more than one channel is enabled, the driver emulates scanning and all channels are sampled in the order they were enabled.

nrfx_err_t nrfx_adc_sample_convert(nrfx_adc_channel_t const *p_channel, nrf_adc_value_t *p_value)

Function for executing a single ADC conversion.

This function selects the desired input and starts a single conversion. If a valid pointer is provided for the result, the function blocks until the conversion is completed. Otherwise, the function returns when the conversion is started, and the result is provided in an event (driver must be initialized in non-blocking mode, otherwise an assertion will fail). The function will fail if ADC is busy. The channel does not need to be enabled to perform a single conversion.

Parameters:

  • p_channel – [in] Channel.

  • p_value – [out] Pointer to the location where the result is to be placed. Unless NULL is provided, the function is blocking.

Return values:

  • NRFX_SUCCESS – Conversion was successful.

  • NRFX_ERROR_BUSY – The ADC driver is busy.

nrfx_err_t nrfx_adc_buffer_convert(nrf_adc_value_t *buffer, uint16_t size)

Function for converting data to the buffer.

If the driver is initialized in non-blocking mode, this function returns when the first conversion is set up. When the buffer is filled, the application is notified by the event handler. If the driver is initialized in blocking mode, the function returns when the buffer is filled.

Conversion is done on all enabled channels, but it is not triggered by this function. This function will prepare the ADC for sampling and then wait for the SAMPLE task. Sampling can be triggered manually by the nrfx_adc_sample function or by PPI using the NRF_ADC_TASK_START task.

Note

If more than one channel is enabled, the function emulates scanning, and a single START task will trigger conversion on all enabled channels. For example: If 3 channels are enabled and the user requests 6 samples, the completion event handler will be called after 2 START tasks.

Note

The application must adjust the sampling frequency. The maximum frequency depends on the sampling timer and the maximum latency of the ADC interrupt. If an interrupt is not handled before the next sampling is triggered, the sample will be lost.

Parameters:

  • buffer – [in] Result buffer.

  • size – [in] Buffer size in samples.

Return values:

  • NRFX_SUCCESS – Conversion was successful.

  • NRFX_ERROR_BUSY – The driver is busy.

bool nrfx_adc_is_busy(void)

Function for retrieving the ADC state.

Return values:

  • true – The ADC is busy.

  • false – The ADC is ready.

NRFX_STATIC_INLINE uint32_t nrfx_adc_start_task_get(void)

Function for getting the address of the ADC START task.

This function is used to get the address of the START task, which can be used to trigger ADC conversion.

Returns:

Start task address.

struct nrfx_adc_done_evt_t
#include <nrfx_adc.h>

ADC driver DONE event structure.

Public Members

nrf_adc_value_t *p_buffer

Pointer to the buffer with converted samples.

uint16_t size

Number of samples in the buffer.

struct nrfx_adc_sample_evt_t
#include <nrfx_adc.h>

SAMPLE event structure.

Public Members

nrf_adc_value_t sample

Converted sample.

struct nrfx_adc_evt_t
#include <nrfx_adc.h>

ADC driver event.

Public Members

nrfx_adc_evt_type_t type

Event type.

nrfx_adc_done_evt_t done

Data for DONE event.

nrfx_adc_sample_evt_t sample

Data for SAMPLE event.

union nrfx_adc_evt_t.[anonymous] data

Union to store event data.

struct nrfx_adc_channel_s
#include <nrfx_adc.h>

ADC channel.

This structure is defined by the user and used by the driver. Therefore, it should not be defined on the stack as a local variable.

Public Members

nrfx_adc_channel_t *p_next

Pointer to the next enabled channel (for internal use).

nrf_adc_config_t config

ADC configuration for the current channel.

struct nrfx_adc_config_t
#include <nrfx_adc.h>

ADC configuration.

Public Members

uint8_t interrupt_priority

Priority of ADC interrupt.