frdm kv31f ADC 讀取正弦波值

Alan_3318a3

使用SDK的ADC中斷範例程式讀取50Hz弦波(如圖1)，發現讀取的波形與假設不符(如圖2)，請問是那些設置有誤?

/*
* Copyright (c) 2013 - 2015, Freescale Semiconductor, Inc.
* Copyright 2016-2018 NXP
* All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*/

#include "fsl_debug_console.h"
#include "pin_mux.h"
#include "clock_config.h"
#include "board.h"
#include "fsl_adc16.h"

/*******************************************************************************
* Definitions
******************************************************************************/
#define DEMO_ADC16_BASE          ADC0
#define DEMO_ADC16_CHANNEL_GROUP 0U
#define DEMO_ADC16_USER_CHANNEL  8U /* PTB0, ADC0_SE8 */

#define DEMO_ADC16_IRQn             ADC0_IRQn
#define DEMO_ADC16_IRQ_HANDLER_FUNC ADC0_IRQHandler

/*******************************************************************************
* Prototypes
******************************************************************************/

/*******************************************************************************
* Variables
******************************************************************************/
volatile bool g_Adc16ConversionDoneFlag = false;
volatile uint32_t g_Adc16ConversionValue;
volatile uint32_t g_Adc16InterruptCounter;
const uint32_t g_Adc16_12bitFullRange = 4096U;

/*******************************************************************************
* Code
******************************************************************************/

void DEMO_ADC16_IRQ_HANDLER_FUNC(void)
{
    g_Adc16ConversionDoneFlag = true;
    /* Read conversion result to clear the conversion completed flag. */
    g_Adc16ConversionValue = ADC16_GetChannelConversionValue(DEMO_ADC16_BASE, DEMO_ADC16_CHANNEL_GROUP);
    g_Adc16InterruptCounter++;
    SDK_ISR_EXIT_BARRIER;
}

/*!
* @brief Main function
*/
int main(void)
{
    adc16_config_t adc16ConfigStruct;
    adc16_channel_config_t adc16ChannelConfigStruct;

    BOARD_InitBootPins();
    BOARD_InitBootClocks();
    BOARD_InitDebugConsole();
    EnableIRQ(DEMO_ADC16_IRQn);

    PRINTF("\r\nADC16 interrupt Example.\r\n");

    /*
     * adc16ConfigStruct.referenceVoltageSource = kADC16_ReferenceVoltageSourceVref;
     * adc16ConfigStruct.clockSource = kADC16_ClockSourceAsynchronousClock;
     * adc16ConfigStruct.enableAsynchronousClock = true;
     * adc16ConfigStruct.clockDivider = kADC16_ClockDivider8;
     * adc16ConfigStruct.resolution = kADC16_ResolutionSE12Bit;
     * adc16ConfigStruct.longSampleMode = kADC16_LongSampleDisabled;
     * adc16ConfigStruct.enableHighSpeed = false;
     * adc16ConfigStruct.enableLowPower = false;
     * adc16ConfigStruct.enableContinuousConversion = false;
     */
    ADC16_GetDefaultConfig(&adc16ConfigStruct);
//    adc16ConfigStruct.clockDivider = kADC16_ClockDivider1;

#ifdef BOARD_ADC_USE_ALT_VREF
    adc16ConfigStruct.referenceVoltageSource = kADC16_ReferenceVoltageSourceValt;
#endif
    ADC16_Init(DEMO_ADC16_BASE, &adc16ConfigStruct);
    ADC16_EnableHardwareTrigger(DEMO_ADC16_BASE, false); /* Make sure the software trigger is used. */
#if defined(FSL_FEATURE_ADC16_HAS_CALIBRATION) && FSL_FEATURE_ADC16_HAS_CALIBRATION
    if (kStatus_Success == ADC16_DoAutoCalibration(DEMO_ADC16_BASE))
    {
        PRINTF("ADC16_DoAutoCalibration() Done.\r\n");
    }
    else
    {
        PRINTF("ADC16_DoAutoCalibration() Failed.\r\n");
    }
#endif /* FSL_FEATURE_ADC16_HAS_CALIBRATION */

    PRINTF("ADC Full Range: %d\r\n", g_Adc16_12bitFullRange);
    PRINTF("Press any key to get user channel's ADC value ...\r\n");

    adc16ChannelConfigStruct.channelNumber                        = DEMO_ADC16_USER_CHANNEL;
    adc16ChannelConfigStruct.enableInterruptOnConversionCompleted = true; /* Enable the interrupt. */
#if defined(FSL_FEATURE_ADC16_HAS_DIFF_MODE) && FSL_FEATURE_ADC16_HAS_DIFF_MODE
    adc16ChannelConfigStruct.enableDifferentialConversion = false;
#endif /* FSL_FEATURE_ADC16_HAS_DIFF_MODE */

    g_Adc16InterruptCounter = 0U;

    while (1)
    {
//        GETCHAR();
        g_Adc16ConversionDoneFlag = false;
        /*
         When in software trigger mode, each conversion would be launched once calling the "ADC16_ChannelConfigure()"
         function, which works like writing a conversion command and executing it. For another channel's conversion,
         just to change the "channelNumber" field in channel configuration structure, and call the function
         "ADC16_ChannelConfigure()"" again.
         Also, the "enableInterruptOnConversionCompleted" inside the channel configuration structure is a parameter for
         the conversion command. It takes affect just for the current conversion. If the interrupt is still required
         for the following conversion, it is necessary to assert the "enableInterruptOnConversionCompleted" every time
         for each command.
        */
        ADC16_SetChannelConfig(DEMO_ADC16_BASE, DEMO_ADC16_CHANNEL_GROUP, &adc16ChannelConfigStruct);
        while (!g_Adc16ConversionDoneFlag)
        {
        }
        PRINTF("ADC Interrupt Count: %d  ", g_Adc16InterruptCounter);
        PRINTF("ADC Value: %d\r\n", g_Adc16ConversionValue);
//        PRINTF("ADC Interrupt Count: %d\r\n", g_Adc16InterruptCounter);
    }
}

圖1

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Alan_3318a3

我找到原因了，線沒接好才這樣，之後將UART的Baudrate 改高一點，就可偵測漂亮的波形