1.14.1 1.15.1 Analog-to-Digital Converter (ADC)
The 12-bit ADC Converter with Threshold Detect includes the following features:
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Successive Approximation Register (SAR) Conversion
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Conversion Speeds of up to 300 ksps
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User-Selectable Resolution of 10 or 12 Bits
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Up to 24 Analog Inputs (internal and external)
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External Voltage Reference Input Pins
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Unipolar Differential Sample-and-Hold Amplifier (SHA)
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Automated Threshold Scan and Compare Operation to Pre-Evaluate Conversion Results
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Selectable Conversion Trigger Source
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Fixed-Length Configurable Conversion Result Buffer
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Eight Options for Result Alignment and Encoding
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Configurable Interrupt Generation
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Operation during CPU Sleep and Idle modes
Using The Library
Interrupt mode:
#include <stddef.h> // Defines NULL #include <stdbool.h> // Defines true #include <stdlib.h> // Defines EXIT_FAILURE #include "definitions.h" // SYS function prototypes #define ADC_VREF (3.3f) #define ADC_MAX_COUNT (1023U) uint16_t adc_count; float input_voltage; volatile bool result_ready = false; // ***************************************************************************** // ***************************************************************************** // Section: Main Entry Point // ***************************************************************************** // ***************************************************************************** void ADC_ResultHandler(uintptr_t context) { /* Read the ADC result */ adc_count = ADC_ResultGet(ADC_RESULT_BUFFER_0); result_ready = true; } int main ( void ) { /* Initialize all modules */ SYS_Initialize ( NULL ); ADC_CallbackRegister(ADC_ResultHandler, (uintptr_t)NULL); printf("\n\r---------------------------------------------------------"); printf("\n\r ADC Demo "); printf("\n\r---------------------------------------------------------\n\r"); while (1) { /* Maintain state machines of all polled MPLAB Harmony modules. */ SYS_Tasks ( ); /* Auto sampling mode is used, so no code is needed to start sampling */ /* Start ADC conversion in software */ ADC_ConversionStart(); /* Wait till ADC conversion result is available */ if(result_ready == true) { result_ready = false; input_voltage = (float)adc_count * ADC_VREF / ADC_MAX_COUNT; printf("ADC Count = 0x%03x, ADC Input Voltage = %d.%02d V \r", adc_count, (int)input_voltage, (int)((input_voltage - (int)input_voltage)*100.0)); } } /* Execution should not come here during normal operation */ return ( EXIT_FAILURE ); }
Library Interface
peripheral library provides the following interfaces:
Functions
Name | Description |
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ADCx_Initialize | Initializes ADC peripheral |
ADCx_Enable | Enable (turn ON) ADC module |
ADCx_Disable | Disable ADC module |
ADC_SamplingStart | Starts the sampling |
ADCx_ConversionStart | Starts the conversion |
ADC_InputSelect | Selects input for ADC |
ADC_InputScanSelect | Selects input for scanning ADC channels |
ADC_ResultIsReady | Returns the status of the channel conversion |
ADC_ResultGet | Provides the ADC conversion result based on the buffer index |
ADCx_CallbackRegister | Registers the function to be called from interrupt |
Data types and constants
Name | Type | Description |
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ADC_RESULT_BUFFER | Enum | Identifies which ADC buffer has to be read |
ADC_INPUT_POSITIVE | Enum | Identifies possible positive input for ADC |
ADC_INPUTS_SCAN | Enum | Identifies possible ADC inputs which can be scanned |
ADC_CALLBACK | Typedef | Defines the data type and function signature for the ADC peripheral callback function |