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adc.h File Reference

ADC (Analog-to-Digital Converter) configuration and control for AVR microcontrollers. More...

#include <avr/io.h>
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Macros

#define ADC_RESOLUTION   ADC_RESSEL_10BIT_gc
 Defines the resolution of the ADC conversion.
#define ADC_CAPACITANCE   1
 Configures the ADC input capacitance setting for the AVR microcontroller.
#define ADC_REFERENCE   ADC_REFSEL_INTREF_gc
 Selects the reference voltage source for the ADC conversions.
#define VREF_REFSEL   VREF_ADC0REFSEL_1V5_gc
 Selects the internal reference voltage level for the ADC when using the internal reference.
#define ADC_PRESCALER   ADC_PRESC_DIV256_gc
 Sets the division factor for the ADC input clock derived from the system clock.
#define ADC_INIT_DELAY   ADC_INITDLY_DLY0_gc
 Defines the ADC clock delay before starting the conversion.
#define ADC_SAMPLE_DELAY_VARIATION   ADC_ASDV_ASVOFF_gc
 Enables or disables automatic sampling delay variation for the ADC.
#define ADC_SAMPLE_DELAY   8
 Configures the delay time between individual ADC sample acquisitions.
#define ADC_SAMPLE_LENGTH   8
 Specifies the sample length duration for ADC conversions.

Typedefs

typedef enum ADC_Accumulation_t ADC_Accumulation
 Alias for enum ADC_Accumulation_t representing ADC sample accumulation modes.
typedef enum ADC_Channel_t ADC_Channel
 Alias for enum ADC_Channel_t representing ADC input channel selections.

Enumerations

enum  ADC_Accumulation_t {
  ADC_Sample_None =ADC_SAMPNUM_ACC1_gc , ADC_Sample_2 =ADC_SAMPNUM_ACC2_gc , ADC_Sample_4 =ADC_SAMPNUM_ACC4_gc , ADC_Sample_8 =ADC_SAMPNUM_ACC8_gc ,
  ADC_Sample_16 =ADC_SAMPNUM_ACC16_gc , ADC_Sample_32 =ADC_SAMPNUM_ACC32_gc , ADC_Sample_64 =ADC_SAMPNUM_ACC64_gc
}
 Defines the number of ADC samples to be accumulated and averaged. More...
enum  ADC_Channel_t {
  ADC_CH0 =ADC_MUXPOS_AIN0_gc , ADC_CH1 =ADC_MUXPOS_AIN1_gc , ADC_CH2 =ADC_MUXPOS_AIN2_gc , ADC_CH3 =ADC_MUXPOS_AIN3_gc ,
  ADC_CH4 =ADC_MUXPOS_AIN4_gc , ADC_CH5 =ADC_MUXPOS_AIN5_gc , ADC_CH6 =ADC_MUXPOS_AIN6_gc , ADC_CH7 =ADC_MUXPOS_AIN7_gc ,
  ADC_CH8 =ADC_MUXPOS_AIN8_gc , ADC_CH9 =ADC_MUXPOS_AIN9_gc , ADC_CH10 =ADC_MUXPOS_AIN10_gc , ADC_CH11 =ADC_MUXPOS_AIN11_gc ,
  ADC_INTREF =ADC_MUXPOS_INTREF_gc , ADC_GND =ADC_MUXPOS_GND_gc
}
 Selects the ADC input channel. More...

Functions

void adc_init (void)
 Initialize the ADC peripheral with pre-configured settings.
void adc_channel (ADC_Channel channel)
 Select the ADC input channel.
void adc_accumulation (ADC_Accumulation samples)
 Set the ADC sample accumulation mode.
void adc_disable (void)
 Disable the ADC module.
unsigned int adc_read (void)
 Perform a single ADC conversion and return the result (polling mode).
unsigned int adc_average (unsigned char samples)
 Perform multiple ADC conversions and return the average result (calculated in software).

Detailed Description

ADC (Analog-to-Digital Converter) configuration and control for AVR microcontrollers.

This header file defines macros, enums, and function prototypes to configure and control the ADC peripheral of AVR microcontrollers. It allows the setup of ADC resolution, reference voltage, prescaler, sample accumulation, and channel selection. The ADC supports customizable parameters including sample delay, sample length, and reference voltage selection. Interrupt handling is not included in this library and should be implemented separately if needed.

Author
g.raf
Date
2025-09-18
Version
1.0 Release
Copyright
Copyright (c) 2025 g.raf Released under the GPLv3 License. (see LICENSE in repository)
Note
This file is part of a larger embedded systems project and subject to the license specified in the repository. For updates and the complete revision history, see the GitHub repository.
See also
https://github.com/0x007e/avr0 "AVR GitHub Repository"

Macro Definition Documentation

◆ ADC_CAPACITANCE

#define ADC_CAPACITANCE   1

Configures the ADC input capacitance setting for the AVR microcontroller.

This macro selects the recommended capacitor setting connected to the ADC input reference pin based on the reference voltage level used. The options are:

  • 0: Recommended for reference voltages below 1V
  • 1: Recommended for higher reference voltages (default)

Proper capacitance selection can improve ADC stability and accuracy by stabilizing the reference voltage.

Note
Ensure that the physical capacitor used on the ADC reference pin matches this setting for optimal performance.

◆ ADC_INIT_DELAY

#define ADC_INIT_DELAY   ADC_INITDLY_DLY0_gc

Defines the ADC clock delay before starting the conversion.

This macro sets the number of ADC clock cycles to wait after enabling the ADC and before starting a conversion. The delay allows the ADC internal circuitry to stabilize, improving conversion accuracy. Possible values with corresponding clock cycles include:

  • ADC_INITDLY_DLY0_gc : 0 cycles (no delay)
  • ADC_INITDLY_DLY16_gc : 16 cycles
  • ADC_INITDLY_DLY32_gc : 32 cycles
  • ADC_INITDLY_DLY64_gc : 64 cycles
  • ADC_INITDLY_DLY128_gc : 128 cycles
  • ADC_INITDLY_DLY256_gc : 256 cycles

The default value is ADC_INITDLY_DLY0_gc (no delay).

Note
Proper delay selection may depend on the ADC configuration and the application requirements. Too small a delay may cause inaccurate conversions.

◆ ADC_PRESCALER

#define ADC_PRESCALER   ADC_PRESC_DIV256_gc

Sets the division factor for the ADC input clock derived from the system clock.

This macro defines the prescaler setting that divides the system clock (F_PER) to generate the ADC clock frequency. The ADC requires an input clock frequency typically between 50 kHz and 1.5 MHz for accurate conversions, especially when using 10-bit resolution.

Valid prescaler options and their division factors include:

  • ADC_PRESC_DIV2_gc : F_PER / 2
  • ADC_PRESC_DIV4_gc : F_PER / 4
  • ADC_PRESC_DIV8_gc : F_PER / 8
  • ADC_PRESC_DIV16_gc : F_PER / 16
  • ADC_PRESC_DIV32_gc : F_PER / 32
  • ADC_PRESC_DIV64_gc : F_PER / 64
  • ADC_PRESC_DIV128_gc : F_PER / 128
  • ADC_PRESC_DIV256_gc : F_PER / 256 (default)

Choosing the appropriate prescaler ensures the ADC clock frequency lies within the recommended range, balancing conversion speed and accuracy.

Note
Incorrect prescaler settings may lead to inaccurate ADC readings or failure to meet timing requirements.

◆ ADC_REFERENCE

#define ADC_REFERENCE   ADC_REFSEL_INTREF_gc

Selects the reference voltage source for the ADC conversions.

This macro defines the reference voltage used by the ADC for analog-to-digital conversions. Options typically include:

  • ADC_REFSEL_INTREF_gc: Internal reference voltage (default)
  • ADC_REFSEL_VDDREF_gc: VDD (power supply) as reference voltage

The chosen reference voltage affects the conversion range and accuracy. The internal reference provides a stable known voltage, whereas VDD varies with supply voltage.

Note
Ensure the selected reference voltage corresponds to the hardware setup for correct ADC readings.

◆ ADC_RESOLUTION

#define ADC_RESOLUTION   ADC_RESSEL_10BIT_gc

Defines the resolution of the ADC conversion.

This macro selects the ADC resolution mode for the AVR microcontroller's ADC. The available options are:

  • ADC_RESSEL_10BIT_gc for 10-bit resolution (default)
  • ADC_RESSEL_8BIT_gc for 8-bit resolution

The resolution affects the precision and size of the ADC conversion result. A higher resolution provides finer granularity but may require longer conversion times.

Note
Choose the resolution based on the application's precision requirements and system constraints.

◆ ADC_SAMPLE_DELAY

#define ADC_SAMPLE_DELAY   8

Configures the delay time between individual ADC sample acquisitions.

This macro defines the number of clock cycles to wait between samples during ADC conversion. Valid values range from 0 to 15 clock cycles. The default value is set to 8 cycles. Adjusting this delay allows tuning of the ADC sampling frequency and can help reduce noise or interference effects.

Note
The optimal delay depends on the specific ADC hardware and application requirements.

◆ ADC_SAMPLE_DELAY_VARIATION

#define ADC_SAMPLE_DELAY_VARIATION   ADC_ASDV_ASVOFF_gc

Enables or disables automatic sampling delay variation for the ADC.

This macro configures whether the ADC hardware automatically varies the delay between sample acquisitions. Options include:

  • ADC_ASDV_ASVOFF_gc : Automatic sampling delay variation disabled (default)
  • ADC_ASDV_ASVON_gc : Automatic sampling delay variation enabled

Enabling this feature randomizes the sampling delay slightly between consecutive ADC conversions, which can help reduce noise and interference effects such as harmonic disturbances in the analog signal.

Note
This feature is especially useful in applications where periodic noise patterns interfere with accurate ADC readings. Disabling it uses a fixed sample delay.

◆ ADC_SAMPLE_LENGTH

#define ADC_SAMPLE_LENGTH   8

Specifies the sample length duration for ADC conversions.

This macro defines the amount of time, in ADC clock cycles, that the ADC samples the input signal before starting the conversion. Valid values range from 0 to 31 cycles. The default value is set to 8 cycles. Longer sample lengths can improve measurement stability and accuracy, especially when measuring high-impedance sources.

Note
Adjust this setting based on the source impedance and noise characteristics of the signal.

◆ VREF_REFSEL

#define VREF_REFSEL   VREF_ADC0REFSEL_1V5_gc

Selects the internal reference voltage level for the ADC when using the internal reference.

This macro defines the exact internal voltage reference selected for the ADC when the ADC_REFERENCE macro is set to ADC_REFSEL_INTREF_gc (internal reference). Possible options include:

  • VREF_ADC0REFSEL_0V55_gc : 0.55 V internal reference
  • VREF_ADC0REFSEL_1V1_gc : 1.1 V internal reference
  • VREF_ADC0REFSEL_1V5_gc : 1.5 V internal reference (default)
  • VREF_ADC0REFSEL_2V5_gc : 2.5 V internal reference

Proper selection of the internal reference voltage is critical for accurate ADC conversions and must match the hardware configuration and application requirements.

Note
This macro is only defined and used if ADC_REFERENCE is set to the internal reference.

Typedef Documentation

◆ ADC_Accumulation

typedef enum ADC_Accumulation_t ADC_Accumulation

Alias for enum ADC_Accumulation_t representing ADC sample accumulation modes.

◆ ADC_Channel

typedef enum ADC_Channel_t ADC_Channel

Alias for enum ADC_Channel_t representing ADC input channel selections.

Enumeration Type Documentation

◆ ADC_Accumulation_t

enum ADC_Accumulation_t

Defines the number of ADC samples to be accumulated and averaged.

This enumeration provides options for accumulating multiple ADC samples into a single averaged result. Accumulation helps reduce noise and increase measurement accuracy by averaging multiple samples.

Values correspond to the number of samples used in accumulation:

  • ADC_Sample_None (1 sample)
  • ADC_Sample_2 (2 samples)
  • ADC_Sample_4 (4 samples)
  • ADC_Sample_8 (8 samples)
  • ADC_Sample_16 (16 samples)
  • ADC_Sample_32 (32 samples)
  • ADC_Sample_64 (64 samples)
Enumerator
ADC_Sample_None 
ADC_Sample_2 
ADC_Sample_4 
ADC_Sample_8 
ADC_Sample_16 
ADC_Sample_32 
ADC_Sample_64 

◆ ADC_Channel_t

enum ADC_Channel_t

Selects the ADC input channel.

This enumeration represents the available analog input channels for the ADC on the AVR microcontroller. It includes external analog input pins, internal reference voltages, and ground.

Channels include:

  • ADC_CH0 to ADC_CH11 : External ADC input pins AIN0 to AIN11
  • ADC_INTREF : Internal reference voltage input
  • ADC_GND : Ground reference input
Enumerator
ADC_CH0 
ADC_CH1 
ADC_CH2 
ADC_CH3 
ADC_CH4 
ADC_CH5 
ADC_CH6 
ADC_CH7 
ADC_CH8 
ADC_CH9 
ADC_CH10 
ADC_CH11 
ADC_INTREF 
ADC_GND 

Function Documentation

◆ adc_accumulation()

void adc_accumulation ( ADC_Accumulation samples)

Set the ADC sample accumulation mode.

Parameters
samplesThe ADC_Accumulation enum value specifying how many ADC samples to accumulate and average.

This function configures the ADC to accumulate multiple samples before producing a conversion result, which helps reduce noise and improve measurement accuracy. The accumulation count is set by writing to the ADC control register B.

Note
The ADC must be configured and enabled for the accumulation mode to take effect.

◆ adc_average()

unsigned int adc_average ( unsigned char samples)

Perform multiple ADC conversions and return the average result (calculated in software).

Parameters
samplesNumber of ADC samples to average.

This function reads the ADC conversion result multiple times by calling adc_read(), sums the results, and calculates the average value to reduce noise and improve stability. It returns the averaged ADC value as an unsigned int.

Note
This method provides a simple software averaging filter for ADC measurements.
Returns
The averaged ADC conversion result.
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◆ adc_channel()

void adc_channel ( ADC_Channel channel)
inline

Select the ADC input channel.

Parameters
channelADC channel to select from the ADC_Channel enumeration.

This inline function sets the ADC multiplexer positive input selection register to the specified channel, masking and shifting the channel value appropriately. The channel selects which analog input pin or internal reference the ADC samples.

Note
Ensure the channel value is valid and corresponds to a supported ADC input.
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◆ adc_disable()

void adc_disable ( void )
inline

Disable the ADC module.

This inline function disables the ADC by clearing the enable bit in the ADC control register. Disabling the ADC conserves power when ADC functionality is not required.

Note
It is recommended to disable the ADC before entering low-power modes to minimize current consumption.
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◆ adc_init()

void adc_init ( void )

Initialize the ADC peripheral with pre-configured settings.

Configures the ADC control registers for capacitance, reference voltage, prescaler, sample delay variation, initial delay, and sample length according to compile-time macros. Enables the ADC with the selected resolution. If the ADC interrupt mode is enabled, the ADC result ready interrupt is also enabled. When using the internal voltage reference, the voltage reference control register is configured accordingly. This function must be called before starting any ADC conversions to ensure proper setup.

Note
Interrupt vectors and ADC interrupt handling routines must be implemented separately when enabling interrupts.
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◆ adc_read()

unsigned int adc_read ( void )

Perform a single ADC conversion and return the result (polling mode).

Starts an ADC conversion by setting the START command bit in the ADC command register. The function then polls the command register until the conversion completes by checking the START bit. After completion, it returns the 16-bit (10-bit ADC result) value from the ADC result register.

Note
This function blocks execution until the conversion is finished.
Returns
The ADC conversion result as an unsigned int.
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