ADC Library

ADC (Analog to Digital Converter) module is available with a number of AVR MCUs. Several library routines are included to provide you comfortable work with the module in single-ended mode.

Library Routines

ADC_Init
ADCx_Init_Advanced
ADC_Get_Sample
ADC_Read

ADC_Init

Prototype	void ADC_Init(); // for XMEGA family of MCUs void ADCx_Init();
Returns	Nothing.
Description	Initializes internal ADC module to work with XTAL frequency prescaled by 128. Clock determines the time period necessary for performing A/D conversion. For XMEGA family of MCUs change the X in the routine prototype with A or B.
Requires	MCU with built-in ADC module.
Example	ADC_Init(); // Initialize ADC module with default settings ADCA_Init(); // Initialize ADC module with default settings

ADCx_Init_Advanced

Prototype

void ADC_Init_Advanced(char Reference);

// for XMEGA family of MCUs

void ADCx_Init_Advanced(unsigned AdcMode, unsigned Reference);

Returns

Nothing.

Description

Initializes internal ADC module to work with user defined settings. For XMEGA family, change the X in the routine prototype with A or B.

Parameters AdcMode and Reference determine the work mode for ADC module and can have the following values:

Description	Predefined library const
Resolution of ADC module - XMEGA MCUs :
`8 bit resolution`	`_ADC_8bit`
`12 bit resolution`	`_ADC_12bit`
Voltage Reference - XMEGA MCUs :
`Internal 1V`	`_ADC_INTERNAL_REF_1V`
`Internal VCC/1.6V`	`_ADC_INTERNAL_REF_VCC`
`External Reference on PORTA`	`_ADC_EXTERNAL_REF_A`
`External Reference on PORTB`	`_ADC_EXTERNAL_REF_B`
Voltage Reference - other MCUs :
`External reference - Aref`	`_ADC_EXTERNAL_REF`
`Internal reference - AVcc`	`_ADC_INTERNAL_REF`
`Internal 0.55V`	`_ADC_INTERNAL_0_55`
`Internal 1.1V`	`_ADC_INTERNAL_1_1`
`Internal 1.5V`	`_ADC_INTERNAL_1_5`
`Internal 2.2V`	`_ADC_INTERNAL_2_2`
`Internal 2.5V`	`_ADC_INTERNAL_2_5`
`Internal 2.56V`	`_ADC_INTERNAL_2_56`
`Internal 4V`	`_ADC_INTERNAL_4`
`Internal 4.3V`	`_ADC_INTERNAL_4_3`

Requires

MCU with built-in ADC module.

Example

ADCA_Init_Advanced(_ADC_12bit, _ADC_INTERNAL_REF_1V);  // Initialize ADC module with 12bit resolution and internal voltage reference of 1V

ADC_Get_Sample

Prototype	unsigned ADC_Get_Sample(unsigned short channel); // for XMEGA family of MCUs unsigned ADCx_Get_Sample(unsigned short channel);
Returns	10-bit or 12-bit unsigned value (MCU dependent) from the specified `channel`.
Description	Routine acquires analog value from the specified channel. Parameter `channel` represents the channel from which the analog value is to be acquired. Refer to the appropriate datasheet for channel-to-pin mapping. For XMEGA family of MCUs change the X in the routine prototype with A or B.
Requires	The MCU with built-in ADC module. Prior to using this routine, ADC module needs to be initialized. See ADC_Init.
Example	unsigned adc_value; ... ADC_Init(); // Initialize ADC module with default settings adc_value = ADC_Get_Sample(2); // Acquire analog value from channel 2

ADC_Read

Prototype	unsigned ADC_Read(char channel); // for XMEGA family of MCUs unsigned ADCx_Read(char channel);
Returns	10-bit or 12-bit unsigned value (MCU dependent) from the specified `channel`.
Description	Routine initializes internal ADC module and acquires analog value from the specified `channel`. Clock determines the time period necessary for performing A/D conversion. Parameter `channel` represents the channel from which the analog value is to be acquired. Refer to the appropriate datasheet for channel-to-pin mapping. For XMEGA family of MCUs change the X in the routine prototype with A or B.
Requires	Nothing.
Example	unsigned adc_value; ... adc_value = ADC_Read(2); // initialize ADC module and acquire analog value from ADC module channel 2

ADC_Set_Active

Prototype	void ADC_Set_Active(unsigned (adc_gs)(unsigned short*));
Description	Sets active ADC module.
Parameters	Parameters : `adc_gs:` ADC_Get_Sample handler.
Returns	Nothing.
Requires	Routine is available only for MCUs with multiple ADC modules. Used ADC module must be initialized before using this routine. See ADC_Init and ADCx_Init_Advanced routines.
Example	// Activate ADC2 module ADC_Set_Active(&ADC2_Get_Sample);
Notes	None.

Library Example

This example code reads analog value from channel 2 and displays it on PORTB and PORTC.

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#include <built_in.h>
unsigned int adc_rd;

void main() {

  DDRB = 0xFF;               // Set PORTB as output
  DDRC = 0xFF;               // Set PORTC as output
  
  while (1) {
    adc_rd = ADC_Read(2);    // get ADC value from 2nd channel
    PORTB = adc_rd;          // display adc_rd[7..0]
    PORTC = Hi(adc_rd);      // display adc_rd[9..8]
  }
}

HW Connection

ADC HW connection

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