msp430 ADC采样保持时间对采样准确度的影响

tianxiaoya

msp430 ADC采样保持时间对采样准确度的影响 [复制链接]

芯片msp430fr5994，用到ADC采集，发现定义不同的采样保持时间得到的数据差距有点大啊，比如，采集一个1.6V左右的信号，4个cycle时的值为1520,64个cycle时的值为1680,192个cycle时的值为1880.不知道是代码写的不正确，还是ADC太差？

tianxiaoya

用过的来一起讨论啊

qwerghf

tianxiaoya 发表于 2017-5-19 13:33
用过的来一起讨论啊

你的驱动代码什么样的，我测试一下

tianxiaoya

void init_clock_DCO16MHZ(void)
{
    //Set DCO frequency to 16MHz
    CS_setDCOFreq(CS_DCORSEL_1, CS_DCOFSEL_4);

    CS_initClockSignal(CS_SMCLK,CS_DCOCLK_SELECT,CS_CLOCK_DIVIDER_1);
    CS_initClockSignal(CS_MCLK,CS_DCOCLK_SELECT,CS_CLOCK_DIVIDER_1);
}

void init_adc(void)
{
    //Set P1.0 as Ternary Module Function Input.
    GPIO_setAsPeripheralModuleFunctionInputPin(
        GPIO_PORT_P1,
        GPIO_PIN0,
        GPIO_TERNARY_MODULE_FUNCTION
        );

    PMM_unlockLPM5();

    //Initialize the ADC12B Module
    /*
     * Base address of ADC12B Module
     * Use internal ADC12B bit as sample/hold signal to start conversion
     * USE smclk as clock source
     * Use default clock divider/pre-divider of 1
     * Not use internal channel
     */
    ADC12_B_initParam initParam = {0};
    initParam.sampleHoldSignalSourceSelect = ADC12_B_SAMPLEHOLDSOURCE_SC;
    initParam.clockSourceSelect = ADC12_B_CLOCKSOURCE_SMCLK;
    initParam.clockSourceDivider = ADC12_B_CLOCKDIVIDER_1;
    initParam.clockSourcePredivider = ADC12_B_CLOCKPREDIVIDER__1;
    initParam.internalChannelMap = ADC12_B_NOINTCH;
    ADC12_B_init(ADC12_B_BASE, &initParam);

    //Enable the ADC12B module
    ADC12_B_enable(ADC12_B_BASE);

    /*
     * Base address of ADC12B Module
     * For memory buffers 0-7 sample/hold for 4 clock cycles
     * For memory buffers 8-15 sample/hold for 4 clock cycles (default)
     * Disable Multiple Sampling
     */
    ADC12_B_setupSamplingTimer(ADC12_B_BASE,
                               ADC12_B_CYCLEHOLD_4_CYCLES,
                               ADC12_B_CYCLEHOLD_4_CYCLES,
                               ADC12_B_MULTIPLESAMPLESDISABLE);

    //Configure Memory Buffer
    /*
     * Base address of the ADC12B Module
     * Configure memory buffer 0
     * Map input A0 to memory buffer 0
     * Vref+ = AVcc
     * Vref- = VSS
     * Memory buffer 0 is not the end of a sequence
     */
    ADC12_B_configureMemoryParam configureMemoryParam = {0};
    configureMemoryParam.memoryBufferControlIndex = ADC12_B_MEMORY_0;
    configureMemoryParam.inputSourceSelect = ADC12_B_INPUT_A0;
    configureMemoryParam.refVoltageSourceSelect =
                    ADC12_B_VREFPOS_AVCC_VREFNEG_VSS;
    configureMemoryParam.endOfSequence = ADC12_B_NOTENDOFSEQUENCE;
    configureMemoryParam.windowComparatorSelect =
        ADC12_B_WINDOW_COMPARATOR_DISABLE;
    configureMemoryParam.differentialModeSelect =
        ADC12_B_DIFFERENTIAL_MODE_DISABLE;
    ADC12_B_configureMemory(ADC12_B_BASE, &configureMemoryParam);

}

tianxiaoya

void main(void)
{
    WDT_A_hold(WDT_A_BASE);

    init_clock_DCO16MHZ();
    init_adc();

    while(1)
    {
        ADC12_B_startConversion(ADC12_B_BASE,
                                                                ADC12_B_MEMORY_0,
                                                                ADC12_B_SINGLECHANNEL);
        vol = ADC12_B_getResults(ADC12_B_BASE, ADC12_B_MEMORY_0);


        if(index_b == 512)
        {
                index_b = 0;
        }

        circularBuffer[index_b++] = vol;
}

tianxiaoya

麻烦版主看一下，msp430的ADC我还没有搞得很清楚，用的CCS

tiankai001

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qwerghf

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tianxiaoya

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tianxiaoya

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火火山

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