CCS/MSP430FR2311: ADC reading only one of channels A3 (P1.3 OA0O) and A0 (P1.0), single conversion mode

Tool/software: Code Composer Studio

Hello all,

I'm trying to read two channels (one after another) in single channel mode (I don't need to convert all of them at once). Problem is, it seems that only one channel is read (the one that starts first), and if I insert 3V3 on it, the reading is  around 2045. Say, if I start conversion on channel A0 first, only A0 will work until the end.

I'm configuring the ADC this way:

void configADC(void)
{
    // Configure ADC A0 pin
    P1SEL0 |= BIT0;
    P1SEL1 |= BIT0;

    // Configure ADC10
    ADCCTL0 &= ~ADCENC;                       // Disable ADC
    ADCCTL0 = ADCSHT_2 | ADCON;               // ADCON, S&H=16 ADC clks
    ADCCTL1 = ADCSHP | ADCCONSEQ_0;           // ADCCLK = MODOSC; sampling timer
    ADCCTL2 = ADCRES;                         // 10-bit conversion results
    ADCIE = ADCIE0;                           // Enable ADC conv complete interrupt
}

And I'm trying to read it this way:

#define A3 true
#define A0 false
uint16_t g_adcResult

uint16_t analogRead(bool channel)
{
    if(channel)
        ADCMCTL0 = ADCINCH_3 | ADCSREF_0;         // A3 ADC input select = OA output Vref = DVCC

    else
        ADCMCTL0 = ADCINCH_0 | ADCSREF_0;         // A0 ADC input select Vref = DVCC

    ADCCTL0 |= ADCENC | ADCSC;          // Sampling and conversion start

    __bis_SR_register(LPM0_bits); // Enter LPM0, ADC_ISR will force exit

    return g_adcResult;
}

void main(void)
{
    uint16_t adcTempTerm = 0;

    //some code...

    adcTempTerm = analogRead(A0) + analogRead(A3);
}

The ADC ISR:

#pragma vector=ADC_VECTOR
__interrupt void ADC_ISR(void)
{
    switch(__even_in_range(ADCIV, ADCIV_ADCIFG))
    {
    case ADCIV_NONE:
        break;

    case ADCIV_ADCOVIFG:
        break;

    case ADCIV_ADCTOVIFG:
        break;

    case ADCIV_ADCHIIFG:
        break;

    case ADCIV_ADCLOIFG:
        break;

    case ADCIV_ADCINIFG:
        break;

    case ADCIV_ADCIFG:

        g_adcResult = ADCMEM0;

        __bic_SR_register_on_exit(LPM0_bits);

        break;

    default:
        break;
    }
}

I'm facing difficulties trying to search information regarding how to properly setup single conversions. Is there a way to achieve what I'm trying to do? Please note that my current program has only 48 bytes of memory left.