ADC Stimulus file with MPLAB SIM (Simulation with MPLAB SIM)

You have to set the configuration bits. Near the end of the device's header file (line 5880 for dsPIC30F4013) is a listing of all the device's configuration bits that need to be set or cleared to ensure proper operation of the device, as well as code comments for how to do it.

For example:

_FOSC( XT & CSW_FSCM_OFF )  // Configure for external XT crystal oscillator, turn off clock switching and monitoring

The oscillator and watchdog timer configurations are very important.

EDIT: In your edited post you tried using the phase-locked loop option for the oscillator. You have to add the following code in your main routine in order to use an external oscillator + PLL:

/*
 *  Set up the PLL for full 60 MIPS operation (dsPIC33EP512MU810)
 *
 *  Fcy = Fin*K/2 --> 60MHz = 8MHz*K/2 --> K = 15
 *  K = M/(N2*N1) --> 15 = M/(N2*N1)   --> N2 = 2, N1 = 2, M = 60
 *  Fcy = 8MHz*15/2 = 60MHz
 *
 *  p. 164-171 datasheet
 */
void configPLL()
{
    PLLFBDbits.PLLDIV = 58; // M = 60
    CLKDIVbits.PLLPOST = 0; // N1 = 2
    CLKDIVbits.PLLPRE = 0;  // N2 = 2
    OSCTUN = 0;
    // Writing to the OSCCON register requires a special unlock sequence
    // Using a compiler built-in write instruction to handle this
    __builtin_write_OSCCONH(0x03);  // Select primary oscillator with PLL   
    __builtin_write_OSCCONL(0x01);  // Request oscillator switch
    while (OSCCONbits.COSC != 0x3); // Wait for the PLL to lock
}

You are not setting the clock signal of the ADC to 32MHz. The parameter ADC_FOSC_32 divides the clock by 32 (see page 225 of the datasheet). This ensures, together with the aquisition time select bits (ADC_4_TAD in your case), the minimum (/maximum) A/D aquisiton time (see page 359). When you hurt these requirements you will not get valid/accurate results.

With the equations given on page 228 you can do the math and verify, that the requirements are met.

Some other points:

• In your code you are never starting the ADC conversion by calling ConvertADC.
• You are configurating port a as output by setting TRISA = 0x0; but you want it to be configured as input (as your comment is saying). TRISA = 0xFF; would configure all pins on port a as input.

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To expand a bit on the aquisiton time (\$T_{AD}\$): This time is needed for the internal circuitry to probably charge. When this time is too short, you will get no/bad results.

For 32Mhz (without divisor) \$T_{AD}\$ would be 31ns. That is too fast. At least 0.7us are required for the ADC to work probably. So you select a proper divisor to get \$T_{AD}\$ above 0.7us. A divisor of 32 will do it here, \$T_{AD} = 1\$us > 0.7us.