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Ref_ADC_config.md

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ADC API Design

The ADC API design in the DxCore library introduces new data structures and functions for configuring and reading analog values from the ADC of a microcontroller or similar device. The new data structure, ADCConfig, allows for easy configuration of various ADC parameters such as conversion mode, resolution, prescaler, sample delay, sample length, and sample number. Additionally, new functions such as analogRead(), analogReadConfig(), getAnalogReadConfig(), analogReadSampleDelay(), analogReadEnableSingleEnded(), analogReadEnableDifferential(), analogReadSampleNum(), and analogReadPrescaler() are introduced for reading and configuring the ADC module.

Data Structures

ADCConfig

Structure for containing all of the ADC configuration parameters:

typedef struct ADCConfig_struct {
    uint8_t convMode;    // ADC conversion mode (single-ended/differential)
    uint8_t muxNeg;      // Negative pin for differential ADC conversion
    uint8_t resolution;  // ADC bit resolution
    uint8_t prescaler;   // ADC clock prescaler value
    uint8_t sampleNum;   // Number of ADC samples to accumulate
    uint8_t sampleDelay; // Delay between ADC samples in accumulation mode
    uint8_t sampleLen;   // ADC sampling time in ADC clock cycles
} ADCConfig;

A default instance of the struct that can be copied to get default config values:

const ADCConfig ADCConfig_default = {
    .convMode = 0,
    .muxNeg = 0x16,
    .resolution = 10,
    .prescaler = ADC_DEFAULT_PRESCALER,
    .sampleNum = 0,
    .sampleDelay = 0,
    .sampleLen = 14
};

Functions

void analogReadConfig(ADCConfig config)

The function takes a single argument config of type ADCConfig, which contains the user-defined configuration settings for the adjusting the ADC module.

Usage Example:

ADCConfig config = ADCConfig_default;
config.sampleNum = ADC_SAMPNUM_ACC8_gc;
config.sampleDelay = ADC_SAMPDLY_DLY10_gc;
// More config if desired...
analogReadConfig(config);

ADCConfig getAnalogReadConfig()

The function retrieves the current configuration settings for the Analog-to-Digital Converter (ADC) and returns them as an ADCConfig structure.

Usage Example:

ADCConfig currentConfig = getAnalogReadConfig();

void analogReadSampleDelay(uint8_t delay)

Set delay in clock cycles between samples when accumulation mode is enabled. Valid values for delay are 0-15. Can be used to suppress periodic noise that would influence the sampling.

Relevant register: ADC0.CTRLD:SAMPDLY

void analogReadEnableSingleEnded()

Change ADC to single-ended mode. In single-ended mode, the ADC conversion result is the input voltage divided by the ADC reference voltage multiplied by a scaling factor. In this mode, only one voltage input needs to selected.

Relevant register: ADC0.CTRLA:CONVMODE

void analogReadEnableDifferential(uint8_t negPin)

Change ADC to differential mode with given negative pin. In differential mode, two voltage inputs are selected and the ADC conversion result is the difference between the two inputs divided by the ADC reference multiplied by a scaling factor.

Relevant registers:

  • ADC0.CTRLA:CONVMODE
  • ADC0.MUXNEG

void analogReadSampleNum(uint8_t samples)

Set the number of consecutive ADC samples to accumulate. Accumulation is disabled by default, when enabled multiple samples will be taken and added together before being returned as the ADC result. Accumulation results in the ADC result having a higher bit resolution and at high accumulation values results in the least-significant bits being dropped.

Valid values for samples:

  • 0: no accumulation
  • 2: 2 samples
  • 4: 4 samples
  • 8: 8 samples
  • 16: 16 samples
  • 32: 32 samples
  • 64: 64 samples
  • 128: 128 samples

Relevant register: ADC0.CTRLB:SAMPNUM:

void analogReadPrescaler(uint8_t prescaler)

Set the prescaler value for the ADC module. The prescaler value adjusts the clock frequency of the ADC module, and by setting a valid prescaler value, the user can adjust the speed and accuracy of the ADC conversion to meet their needs.

Valid values for prescaler:

  • 2: clock divided by 2
  • 4: clock divided by 4
  • 8: clock divided by 8
  • 12: clock divided by 12
  • 16: clock divided by 16
  • 20: clock divided by 20
  • 24: clock divided by 24
  • 28: clock divided by 28
  • 32: clock divided by 32
  • 48: clock divided by 48
  • 64: clock divided by 64
  • 96: clock divided by 96
  • 128: clock divided by 128
  • 256: clock divided by 256

Relevant register: `ADC0.CTRLC:PRESC