An ADC, or Analog-to-Digital Converter, is a device that turns analog signals, like sound or temperature, into digital data that a computer or microcontroller can understand. It measures the analog voltage and converts it into a digital value that can be used by digital systems for processing, storage, or display.

Warning

The ADC API is an advanced interface provided for users with technical background. For most data acquisition tasks, use the Data API which provides a more user-friendly and higher-level entry point.

Pinout

SPIN boards have 5 independant ADC units. Each unit can measure multiple analog signals, using a measurment sequence.

Capabilities

Each ADC channel has : - 12 bit resolution: 0b to 4096b - Sensing full scale: 0V to 2.048V - Sampling time down to 42ns

SPIN v1.1.0SPIN v1.0.0

SPIN_1_1_0_ADC_pinout_main SPIN_1_1_0_ADC_pinout_inner

SPIN_1_0_0_ADC_pinout_main SPIN_1_0_0_ADC_pinout_inner

Info

ADC12 means that the pin can be used either as ADC1 or ADC2
INx means that it is channel x.

Include

Note

#include <SpinAPI.h>

Make sure that SPIN API is included to use AdcHAL

Initialization sequence

Note

Software triggeredHardware triggered

Link an adc trigger event to the ADC spin.adc.configureTriggerSource(ADCx, TRIG)
Define acquisition sequence by enabling adc channel : spin.adc.enableChannel(ADCx, channelx)
trigger an adc data.triggerAcquisition()
Retrieve value : data.getLatest(ADCx, pinx)

1. Make sure PWM engine is initialized 2. Link an adc trigger event to the ADC spin.adc.configureTriggerSource(ADCx, TRIG) 3. Set continuous/discontinuous conversion mode. Optional : spin.adc.configureDiscontinuousMode(x, 0/1) 4. Define acquisition sequence by enabling adc channel : spin.adc.enableChannel(ADCx, channelx) 6. Start data dispatching to get acquired values data.start() 7. Retrieve value : data.getLatest(ADCx, pinx)

Example

Software triggeredHardware triggered

spin.adc.configureTriggerSource(1, software);
spin.adc.enableChannel(1, 30);
data.triggerAcquisition(1);
float32_t adc_value =   data.getLatest(1, 30);

/* PWM unit initialization */
spin.pwm.setModulation(PWMA, UpDwn);
spin.pwm.setAdcEdgeTrigger(PWMA, EdgeTrigger_up);
spin.pwm.setAdcDecimation(PWMA, 1);
spin.pwm.setMode(PWMA, VOLTAGE_MODE);
spin.pwm.initUnit(PWMA);
spin.pwm.setDeadTime(PWMA, 200,200);
spin.pwm.setAdcTrigger(PWMA, ADCTRIG_1);
spin.pwm.enableAdcTrigger(PWMA);
spin.pwm.setDutyCycle(0.5);
spin.pwm.startDualOutput(PWMA);

/* ADC initialization */
spin.adc.configureTriggerSource(1, hrtim_eev1);
spin.adc.configureDiscontinuousMode(1,1);
spin.adc.enableChannel(1, 30);
data.start();
float32_t adc_value =   data.getLatest(1, 30);

Channel sequence

Each ADC unit can measure multiple analog signal. This works by defining an acquisition sequence.

Tip

By default the aquisition sequence is in continuous mode. It means than one trigger will trigger all the sequence of acquisition. This can be changed using Discontinuous Mode

Example

3 channels on ADC1

spin.adc.enableChannel(1, 2)
spin.adc.enableChannel(1, 3)
spin.adc.enableChannel(1, 1)

In this example, for each trigger action, the ADC1 will measure channel 2, then channel 3, then channel 1.

Single channel

spin.adc.enableChannel(1, 1)

In this example, for each trigger, the ADC1 will measure channel 1.

Note

Sequence order is given by spin.adc.enableChannel() order.

Software triggered

adc software triggers

A software trigger for an ADC is a command or signal generated by the software to start the ADC conversion process. Instead of using a hardware signal or event to initiate the conversion, the ADC is triggered by software instructions, allowing for precise control and synchronization with other software processes or events. For example this trigger command can be generated from a high speed control task.

spin.adc.configureTriggerSource(2, software); // ADC 2 configured in software mode
data.triggerAcquisition(2); // Send an adc trigger to ADC2 to start conversion
adc_value = data.getLatest(2, 35); // Get the acquired data

Example

See the following example for an application :

Software trigerred ADC

Synchronous with PWMs

Software triggers is generally speaking not suitable for applications that requires precise timing. Sometimes measurement have to be taken at a specific time, in interaction with the control signal.

Info

This kind of acquisition have a side benefit. It operates in the background and does not interfer with software. It means that periodical sampling will not interrupt code execution.

The trigger is the PWM peripheral, the ADC performs the conversion and place the result in an output buffer, the output buffer is directly placed in memory by a DMA. A rather complex software mechanics execute periodically and serve each measurement in a dedicated memory space. The periodical routine is executed at the beggining of the controlTask.

Info

Synchronous measurement require having a controlTask running.

Tip

This page informs on how to parameters the triggering of the measurement To retrieve measurement values please refer to DataAPI

The section below explain how to synchronize measurements with control signals.

Note

These features are available for ADC1 and ADC2.

The different event and trigger of ADC/HRTIM

You might have seen that there are differents variables referencing adc trigger :

spin.adc.configureTriggerSource(1, hrtim_eev1);
spin.pwm.setAdcTrigger(PWMA, ADCTRIG_1);

There is hrtim_eevx or ADCTRIG_x, let's see the role of each of them.

ADCTRIG_x

In the PWM API, four signals can serve as ADC triggers, initiating ADC conversions: ADC_TRIG1, ADC_TRIG2, ADC_TRIG3, and ADC_TRIG4.

The PWM is produced by a carrier (see here) by using a comparator to compare a specific constant value with the carrier, we can generate an event when enabling a trigger on the PWM. For instance :

spin.pwm.setAdcTrigger(PWMA, ADCTRIG_1);
spin.pwm.enableAdcTrigger(PWMA);

We are enabling and linking ADCTRIG_1 to PWMA. That means that when the comparator value and the carrier value of the PWMA we can generate an event from ADCTRIG_1 that can be used to start an ADC conversion :

ADC trigger

The comparator value can be adjusted using the function spin.pwm.setAdcTriggerInstant(PWMA, 0.5). For example, setting it to 0.5 means triggering an event halfway through the switching period, initiating an ADC conversion.

hrtim_eevx

An ADC conversion can be initiated either by software (via a function) or hardware through an external event. Numerous external events exist, but some are specifically related to PWM: hrtim_eev1, hrtim_eev2, hrtim_eev3, and hrtim_eev4.

Each of these external events is associated with events generated by ADCTRIG_x. For instance, hrtim_eev1 is linked to ADCTRIG_1, and so on.

spin.pwm.setAdcTrigger(PWMA, ADCTRIG_1);
spin.pwm.enableAdcTrigger(PWMA);
spin.adc.configureTriggerSource(1, hrtim_eev1);

The above code indicates that we've connected ADC1 to the external event hrtim_eev1, which, in turn, is connected to the event generated by ADCTRIG1 when the comparator (set by the trigger value) matches the carrier of PWMA.

Source ADC and PWM channel

ADC1 and ADC2 can be associated with PWM channels at will.

function configureDiscontinuousMode

Set the discontinuous count for an ADC. By default, ADCs are not in discontinuous mode.

void AdcHAL::configureDiscontinuousMode (
    uint8_t adc_number,
    uint32_t dicontinuous_count
)

Applied configuration will only be set when ADC is started. If ADC is already started, it must be stopped then started again.

Parameters:

adc_number Number of the ADC to configure.
discontinuous_count Number of channels to acquire on each trigger event. 0 to disable discontinuous mode (default).

ADC1 and PWMAADC1 and PWMC

left_aligned_ADC_50

    spin.pwm.setAdcTrigger(PWMA, ADCTRIG_1);
    spin.pwm.enableAdcTrigger(PWMA);

left_aligned_ADC_PWM_C

    spin.pwm.setAdcTrigger(PWMC, ADCTRIG_1);
    spin.pwm.enableAdcTrigger(PWMC);

Modulation impact

Note

Hardware trigger depends on PWM modulation.

Left Aligned ModulationCenter aligned modulation

left_aligned_ADC_50

    spin.pwm.setAdcTrigger(PWMA, ADCTRIG_1);
    spin.pwm.enableAdcTrigger(PWMA);

center_aligned_ADC_rising_edge

    spin.pwm.setAdcTrigger(PWMA, ADCTRIG_1);
    spin.pwm.enableAdcTrigger(PWMA);

Rising Edge / Falling edge

Note

This only applies to center aligned modulation.

Rising EdgeFalling Edge

center_aligned_ADC_rising_edge

    spin.pwm.setAdcEdgeTrigger(PWMA, EdgeTrigger_up);
    spin.pwm.setAdcTrigger(PWMA, ADCTRIG_1);
    spin.pwm.enableAdcTrigger(PWMA);

center_aligned_ADC_falling_edge

    spin.pwm.setAdcEdgeTrigger(PWMA, EdgeTrigger_down);
    spin.pwm.setAdcTrigger(PWMA, ADCTRIG_1);
    spin.pwm.enableAdcTrigger(PWMA);

Measurment trigger instant

Trigger timing can be defined or changed dynamically.

20% Duty cycle80% Duty cycle

left_aligned_ADC_20

    spin.pwm.setAdcTriggerInstant(PWMA, 0.2);

left_aligned_ADC_80

    spin.pwm.setAdcTriggerInstant(PWMA, 0.8);

Continuous / Discontinuous sequence

Note

This is relevant if more than one measurement is taken with the same ADC.

Continuous sequenceDiscontinuous sequence

left_aligned_continuous_sampling

    spin.adc.configureDiscontinuousMode(1, 0);

left_aligned_ADC_50

    spin.adc.configureDiscontinuousMode(1, 1);

Number of PWM period between acquisition

Note

This is relevant if more than one measurement is taken with the same ADC.

With 2 periodsWith 4 periodsWithout interuptions

sparse_sampling_2

    spin.pwm.setAdcTriggerPostScaler(PWMA, 2);

sparse_sampling_4

    spin.pwm.setAdcTriggerPostScaler(PWMA, 4);

left_aligned_continuous_sampling

    spin.pwm.setAdcTriggerPostScaler(PWMA, 1);

Example

see the following example for an application :

PWM trigerred ADC

API Reference

Class AdcHAL

ClassList > AdcHAL

Handles the ADC for the spin board. More...

#include <AdcHAL.h>

Public Functions

Type	Name
void	configureDiscontinuousMode (uint8_t adc_number, uint32_t dicontinuous_count) Set the discontinuous count for an ADC. By default, ADCs are not in discontinuous mode.
void	configureTriggerSource (uint8_t adc_number, adc_ev_src_t trigger_source) Change the trigger source of an ADC. By default, triggger source for ADC 1/2 is on HRTIM1, and ADC 3/4 is software-triggered.
void	disableChannel (uint8_t adc_number, uint8_t channel) Removes a channel from the list of channels that are acquired by an ADC.
void	enableChannel (uint8_t adc_number, uint8_t channel) Add a channel to the list of channels to be acquired for an ADC. The order in which channels are acquired is determined by the order in which they are enabled.
void	enableDma (uint8_t adc_number, bool use_dma) ADC DMA mode configuration. Enables DMA and circular mode on an ADC.
uint32_t	getEnabledChannelsCount (uint8_t adc_number) Returns the number of enabled channels for an ADC.
void	startAllAdcs () Start all configured ADCs.
void	stopAllAdcs () Stop all configured ADCs.
void	triggerSoftwareConversion (uint8_t adc_number, uint8_t number_of_acquisitions) Triggers a conversion on an ADC which is configured as software triggered.

Detailed Description

Note:

Use this element to call functions linked to the ADC for the SPIN board

Public Functions Documentation

function configureDiscontinuousMode

Set the discontinuous count for an ADC. By default, ADCs are not in discontinuous mode.

void AdcHAL::configureDiscontinuousMode (
    uint8_t adc_number,
    uint32_t dicontinuous_count
)

Applied configuration will only be set when ADC is started. If ADC is already started, it must be stopped then started again.

Parameters:

adc_number Number of the ADC to configure.
discontinuous_count Number of channels to acquire on each trigger event. 0 to disable discontinuous mode (default).

function configureTriggerSource

Change the trigger source of an ADC. By default, triggger source for ADC 1/2 is on HRTIM1, and ADC 3/4 is software-triggered.

void AdcHAL::configureTriggerSource (
    uint8_t adc_number,
    adc_ev_src_t trigger_source
)

Applied configuration will only be set when ADC is started. If ADC is already started, it must be stopped then started again.

Parameters:

adc_number Number of the ADC to configure
trigger_source Source of the trigger

function disableChannel

Removes a channel from the list of channels that are acquired by an ADC.

void AdcHAL::disableChannel (
    uint8_t adc_number,
    uint8_t channel
)

Note:

If a channel has been enabled multiple times, then only the first occurence in the list will be removed.

Applied configuration will only be set when ADC is started. If ADC is already started, it must be stopped then started again.

Parameters:

adc_number Number of the ADC to configure.
channel Number of the channel to to no longer be acquired.

function enableChannel

Add a channel to the list of channels to be acquired for an ADC. The order in which channels are acquired is determined by the order in which they are enabled.

void AdcHAL::enableChannel (
    uint8_t adc_number,
    uint8_t channel
)

Applied configuration will only be set when ADC is started. If ADC is already started, it must be stopped then started again.

Parameters:

adc_number Number of the ADC to configure.
channel Number of the channel to to be acquired.

function enableDma

ADC DMA mode configuration. Enables DMA and circular mode on an ADC.

void AdcHAL::enableDma (
    uint8_t adc_number,
    bool use_dma
)

Applied configuration will only be set when ADC is started. If ADC is already started, it must be stopped then started again.

Parameters:

adc_num Number of the ADC on which to enable DMA.
use_dma Set to true to use DMA for this ADC, false to not use it (default).

function getEnabledChannelsCount

Returns the number of enabled channels for an ADC.

uint32_t AdcHAL::getEnabledChannelsCount (
    uint8_t adc_number
)

Parameters:

adc_number Number of the ADC to fetch.

Returns:

Number of enabled channels on the given ADC.

function startAllAdcs

Start all configured ADCs.

void AdcHAL::startAllAdcs ()

function stopAllAdcs

Stop all configured ADCs.

void AdcHAL::stopAllAdcs ()

function triggerSoftwareConversion

Triggers a conversion on an ADC which is configured as software triggered.

void AdcHAL::triggerSoftwareConversion (
    uint8_t adc_number,
    uint8_t number_of_acquisitions
)

Note:

Software trigger is default for all ADCs unless configured differently by the user or another module.

Parameters:

adc_number Number of the ADC to fetch.
number_of_acquisitions Number of channels to acquire.

The documentation for this class was generated from the following file docs/core/zephyr/modules/owntech_spin_api/zephyr/src/AdcHAL.h