TMS320F280033: ADC采样结果只有实际的一半

程序中ADC转换结果只有实际值的一半，比如1.52V的输入电压，ADC结果为930，而实际ADC结果应该为 (1.52/3.3)*4096=1886

检查自己的工程，没有发现配置问题，然后用Ti的例程adc_ex1_soc_epwm来测试，结果仍然如此。

ADC采用内部参考电压3.3V

TI例程中的部分代码：

void initADC(void)
{
    //
    // Setup VREF as internal
    //
    SetVREF(ADC_ADCA, ADC_INTERNAL, ADC_VREF3P3);

    EALLOW;

    //
    // Set ADCCLK divider to /4
    //
    AdcaRegs.ADCCTL2.bit.PRESCALE = 6;

    //
    // Set pulse positions to late
    //
    AdcaRegs.ADCCTL1.bit.INTPULSEPOS = 1;

    //
    // Power up the ADC and then delay for 1 ms
    //
    AdcaRegs.ADCCTL1.bit.ADCPWDNZ = 1;
    EDIS;

    DELAY_US(1000);
}


void SetVREF(int module, int mode, int ref)
{
    Uint16 *offset, offsetShiftVal;

    if((mode == ADC_INTERNAL) && (ref == ADC_VREF3P3))
    {
        offsetShiftVal = 8U;         // Internal / 1.65v mode offset
    }
    else
    {
        offsetShiftVal = 0U;        // All other modes
    }

    //
    // Set up pointer to offset trim in OTP for ADCA.
    //
    offset = (Uint16 *)((Uint32)0x7016CU);

    EALLOW;

    //
    // Get offset trim from OTP and write it to the register for ADCA.
    //
    AdcaRegs.ADCOFFTRIM.bit.OFFTRIM = (*offset >> offsetShiftVal) & 0xFFU;

    //
    // Set up pointer to offset trim in OTP for ADCB.
    //
    offset = (Uint16 *)((Uint32)0x7016DU);

    //
    // Get offset trim from OTP and write it to the register for ADCB.
    //
    AdcbRegs.ADCOFFTRIM.bit.OFFTRIM = (*offset >> offsetShiftVal) & 0xFFU;

    //
    // Set up pointer to offset trim in OTP for ADCC.
    //
    offset = (Uint16 *)((Uint32)0x7016EU);

    //
    // Get offset trim from OTP and write it to the register for ADCC.
    //
    AdccRegs.ADCOFFTRIM.bit.OFFTRIM = (*offset >> offsetShiftVal) & 0xFFU;

    //
    // Configure the reference mode for all ADCs (internal or external).
    //
    AnalogSubsysRegs.ANAREFCTL.bit.ANAREFSEL = mode;

    //
    // Configure the reference voltage for all ADCs (3.3V or 2.5V).
    //
    AnalogSubsysRegs.ANAREFCTL.bit.ANAREF2P5SEL = ref;

    EDIS;
}

void initADCSOC(void)
{
    //
    // Select the channels to convert and the end of conversion flag
    //
    EALLOW;

    AdcaRegs.ADCSOC0CTL.bit.CHSEL = 1;     // SOC0 will convert pin A1
                                           // 0:A0  1:A1  2:A2  3:A3
                                           // 4:A4   5:A5   6:A6   7:A7
                                           // 8:A8   9:A9   A:A10  B:A11
                                           // C:A12  D:A13  E:A14  F:A15
    AdcaRegs.ADCSOC0CTL.bit.ACQPS = 9;     // Sample window is 10 SYSCLK cycles
    AdcaRegs.ADCSOC0CTL.bit.TRIGSEL = 5;   // Trigger on ePWM1 SOCA

    AdcaRegs.ADCINTSEL1N2.bit.INT1SEL = 0; // End of SOC0 will set INT1 flag
    AdcaRegs.ADCINTSEL1N2.bit.INT1E = 1;   // Enable INT1 flag
    AdcaRegs.ADCINTFLGCLR.bit.ADCINT1 = 1; // Make sure INT1 flag is cleared

    EDIS;
}