Constants and function specific to the nRF52 SAADC peripheral. More...

#include <nrfcxx/nrf52/impl.hpp>

Inheritance diagram for nrfcxx::nrf5::series::SAADC_Peripheral:

Public Types
using	mutex_type = mutex_irq< static_cast< IRQn_Type >(nrf5::SAADC.IRQn)>

Static Public Member Functions
static constexpr bool	near_zero (uint16_t v_adc16)
	Test whether a value appears to be indistinguishable from zero. More...

static constexpr unsigned int	make_config (unsigned int refsel=SAADC_CH_CONFIG_REFSEL_Internal, unsigned int gain=SAADC_CH_CONFIG_GAIN_Gain1_6, unsigned int tacq=SAADC_CH_CONFIG_TACQ_10us, bool burst=true, unsigned int resp=SAADC_CH_CONFIG_RESP_Bypass, bool differential=false, unsigned int resn=SAADC_CH_CONFIG_RESN_Bypass)
	Helper to build up a ADC channel-specific `CONFIG` value. More...

static bool	busy ()

static void	enable_bi ()

static void	disable_bi ()

static int	calibrate_bi ()

static int	start_bi ()

static void	stopped_bi ()

static unsigned int	normalize_bi ()
	Post-process the ADC results so they're normalized as if from a 16-bit ADC. More...

Static Public Member Functions inherited from nrfcxx::nrf5::series::ADC_Base
static void	setup_result_bi (volatile uint16_t *ptr, uint16_t maxcnt=1)
	Record the destination address and count of ADC samples. More...

Static Public Attributes
static constexpr IRQn_Type	IRQn = SAADC_IRQn

static constexpr unsigned int	VBG_mV = 600
	nRF52 reference voltage is 0.6 V.

static constexpr uint16_t	TOLERANCE_adc16 = (1U << 7)
	The value corresponding to the 9th bit of a normalized acquisition. More...

static constexpr uint32_t	inten

static bool	calibrating_bi_

Static Public Attributes inherited from nrfcxx::nrf5::series::ADC_Base
static volatile uint16_t *	result_ptr_

static uint16_t	result_maxcnt_

Detailed Description

Constants and function specific to the nRF52 SAADC peripheral.

Note: The SAADC peripheral has much higher noise than the ADC peripheral of nRF51. Significant oversampling is required for reasonable results, and it's likely the low bits should simply be discarded.; SAADC has a +/- 2 LSB (0.19%) error tolerance for offset at 10 bit resolution. This can cause voltages near ground to be negative, which appears as extremely high voltages. There is also a +/- 3% error due to gain (+4% for gain >= 0.5).; So, basically, assume you only get 9 bits out of this thing.

See also: https://devzone.nordicsemi.com/f/nordic-q-a/12287/nrf52-saadc-noise

Member Function Documentation

◆ make_config()

static constexpr unsigned int nrfcxx::nrf5::series::SAADC_Peripheral::make_config	(	unsigned int	refsel = `SAADC_CH_CONFIG_REFSEL_Internal`,
		unsigned int	gain = `SAADC_CH_CONFIG_GAIN_Gain1_6`,
		unsigned int	tacq = `SAADC_CH_CONFIG_TACQ_10us`,
		bool	burst = `true`,
		unsigned int	resp = `SAADC_CH_CONFIG_RESP_Bypass`,
		bool	differential = `false`,
		unsigned int	resn = `SAADC_CH_CONFIG_RESN_Bypass`
	)

inlinestaticconstexpr

Helper to build up a ADC channel-specific CONFIG value.

Parameters

refsel	one of: `SAADC_CH_CONFIG_REFSEL_Internal` for internal 600 mV reference default; `SAADC_CH_CONFIG_REFSEL_VDD1_4` for VDD/4 as reference;
gain	one of: `SAADC_CH_CONFIG_GAIN_Gain1_6` for a gain of 1/6 default; `SAADC_CH_CONFIG_GAIN_Gain1_5` for a gain of 1/5; `SAADC_CH_CONFIG_GAIN_Gain1_4` for a gain of 1/4; `SAADC_CH_CONFIG_GAIN_Gain1_3` for a gain of 1/3; `SAADC_CH_CONFIG_GAIN_Gain1_2` for a gain of 1/2; `SAADC_CH_CONFIG_GAIN_Gain1` for a gain of 1; `SAADC_CH_CONFIG_GAIN_Gain2` for a gain of 2; `SAADC_CH_CONFIG_GAIN_Gain4` for a gain of 4.
tacq	one of: `SAADC_CH_CONFIG_TACQ_3us` for 3 us; `SAADC_CH_CONFIG_TACQ_5us` for 5 us; `SAADC_CH_CONFIG_TACQ_10us` for 10 us default; `SAADC_CH_CONFIG_TACQ_15us` for 15 us; `SAADC_CH_CONFIG_TACQ_20us` for 20 us; `SAADC_CH_CONFIG_TACQ_40us` for 40 us.
burst	one of: `true` for burst mode operation non-standard default (this is default enabled to support non-zero `OVERSAMPLING` with the simplified one-shot periph::ADCClient API.) `false` for normal operation;
resp	one of: `SAADC_CH_CONFIG_RESP_Bypass` to bypass the resistor ladder default; `SAADC_CH_CONFIG_RESP_Pulldown` to pull-down to GND; `SAADC_CH_CONFIG_RESP_Pullup` to pull-up to VDD; `SAADC_CH_CONFIG_RESP_VDD1_2` to set input at VDD/2.
differential	one of: `false` for single ended default; `true` for differential.
resn	one of: `SAADC_CH_CONFIG_RESN_Bypass` to bypass the resistor ladder default; `SAADC_CH_CONFIG_RESN_Pulldown` to pull-down to GND; `SAADC_CH_CONFIG_RESN_Pullup` to pull-up to VDD; `SAADC_CH_CONFIG_RESN_VDD1_2` to set input at VDD/2.

◆ near_zero()

static constexpr bool nrfcxx::nrf5::series::SAADC_Peripheral::near_zero ( uint16_t v_adc16 )

inlinestaticconstexpr

Test whether a value appears to be indistinguishable from zero.

This tests whether a normalized ADC result is within TOLERANCE_adc16 of zero, handling the case where the SAADC result was a small negative that appears as a large unsigned measurement.

Parameters

v_adc16 a normalized ADC result.

Returns: true iff the value is within TOLERANCE_adc16 of zero.

◆ normalize_bi()

static unsigned int nrfcxx::nrf5::series::SAADC_Peripheral::normalize_bi ( )

inlinestatic

Post-process the ADC results so they're normalized as if from a 16-bit ADC.

This is done in-place in the memory to which the results were DMAd.

Field Documentation

◆ inten

constexpr uint32_t nrfcxx::nrf5::series::SAADC_Peripheral::inten

staticconstexpr

Initial value:

= 0
    | (SAADC_INTENSET_CALIBRATEDONE_Set << SAADC_INTENSET_CALIBRATEDONE_Pos)
    | (SAADC_INTENSET_STARTED_Set << SAADC_INTENSET_STARTED_Pos)
    | (SAADC_INTENSET_DONE_Set << SAADC_INTENSET_DONE_Pos)
    | (SAADC_INTENSET_RESULTDONE_Set << SAADC_INTENSET_RESULTDONE_Pos)
    | (SAADC_INTENSET_END_Set << SAADC_INTENSET_END_Pos)
    | (SAADC_INTENSET_STOPPED_Set << SAADC_INTENSET_STOPPED_Pos)

◆ TOLERANCE_adc16

constexpr uint16_t nrfcxx::nrf5::series::SAADC_Peripheral::TOLERANCE_adc16 = (1U << 7)

staticconstexpr

The value corresponding to the 9th bit of a normalized acquisition.

See above for discussion of SAADC error bounds.

The documentation for this struct was generated from the following file:

nrfcxx/nrf52/impl.hpp

Public Types

Static Public Member Functions

Static Public Attributes