dsPIC: ¿pierdo la funcionalidad del puerto en un pin CN?

Estoy probando algunos códigos con un dsPIC33FJ32MC102 en el MPLAB X con XC16. Tengo algunos interruptores dip conectados a RB0-RB2 que quiero usar para cambiar los LED conectados a RB7-RB9. Puedo hacer que los LED se enciendan manualmente con una instrucción LATB = 0x380, sin embargo, cuando enciendo los interruptores no pasa nada. He probado los interruptores y el cableado y he comprobado que todo está correcto, y por lo que puedo decir, mi código es correcto. Basándome en todas las hojas de datos que he leído, todavía debería obtener la E / S del puerto en una entrada de CN, ¿por qué no funciona esto?

Aquí está mi código (en un estado primordial, por lo que todas las configuraciones aún son detalladas):

// DSPIC33FJ32MC102 Configuration Bit Settings

// 'C' source line config statements

#define FOSC    (3686400ULL)
#define FCY     (FOSC/2)

#include <xc.h>
#include <libpic30.h>

// CONFIG2
#pragma config POSCMOD = NONE           // Primary Oscillator Select (Primary oscillator disabled)
#pragma config ALTI2C = OFF             // Alternate I2C pins (I2C mapped to SDA1/SCL1)
#pragma config LPOL = ON                // Motor Control PWM Low Side Polarity bit (PWM module low side output pins have active-high output polarity)
#pragma config IOL1WAY = ON             // IOLOCK Protection (Allow Only One Re-configuration)
#pragma config OSCIOFNC = ON            // Primary Oscillator Output Function (OSC2 pin has digital I/O function)
#pragma config FCKSM = CSDCMD           // Clock Switching and Monitor (Clock switching and Fail-Safe Clock Monitor are disabled)
#pragma config FNOSC = FRCDIVN          // Oscillator Mode (Internal Fast RC (FRC) with divide by N)
#pragma config WDTWIN = WDTWIN25        // Watchdog Window Select (Watchdog Window is 25% of WDT period)
#pragma config PWMPIN = ON              // Motor Control PWM Module Pin Mode bit (PWM module pins controlled by PORT register at device Reset)
#pragma config PWMLOCK = ON             // PWM Lock Enable (Certain PWM registers may only be written after key sequence)
#pragma config IESO = ON                // Internal External Switch Over Mode (Start-up device with FRC, then automatically switch to user-selected oscillator source when ready)

// CONFIG1
#pragma config WDTPOST = PS32768        // Watchdog Timer Postscaler (1:32,768)
#pragma config WDTPRE = PR128           // WDT Prescaler (Prescaler ratio of 1:128)
#pragma config PLLKEN = ON              // PLL Lock Enable (Clock switch to PLL source will wait until the PLL lock signal is valid.)
#pragma config WINDIS = OFF             // Watchdog Timer Window (Watchdog Timer in Non-Window mode)
#pragma config FWDTEN = OFF             // Watchdog Timer Enable (Watchdog timer enabled/disabled by user software)
#pragma config ICS = PGD3               // Comm Channel Select (Communicate on PGEC3/PGED3)
#pragma config HPOL = ON                // Motor Control PWM High Side Polarity bit (PWM module high side output pins have active-high output polarity)
#pragma config GWRP = ON                // General Code Segment Write Protect (Writes to program memory are disabled)
#pragma config GCP = OFF                // General Segment Code Protection (General Segment Code protect is disabled)

char t1ctr = 0;
unsigned short PAin     = 0;
unsigned short PAout    = 0;
unsigned short PBin     = 0;
unsigned short PBout    = 0;

void __attribute__((__interrupt__, __auto_psv__)) _T1Interrupt(void){
    t1ctr++;
    if(t1ctr==40){              //after 1 second
        t1ctr = 0;
        LATAbits.LATA1 ^= 1;    //toggle the LED
    }

    IFS0bits.T1IF = 0;
}

void __attribute__((__interrupt__, __auto_psv__)) _CNInterrupt(void){
    PBin = PORTB;       //Read the port
    PBin &= 0x0007;     //get only the inputs
    PBout = PBin << 7;  //move them out to the outputs
    LATB = PBout;       
    IFS1bits.CNIF = 0;
}

void main(void){

//OSCILLATOR CONFIGS
    CLKDIVbits.ROI      = 0;
    CLKDIVbits.FRCDIV   = 0b001; //3.68MHz
    CLKDIVbits.DOZEN    = 0;
    OSCTUNbits.TUN      = 0b00000;
    OSCCONbits.CLKLOCK  = 1;

//PERIPHERAL CONFIGS
    //enable only Timer 1, PWM, and ADC
    PMD1bits.T5MD       = 1;
    PMD1bits.T4MD       = 1;
    PMD1bits.T3MD       = 1;
    PMD1bits.T2MD       = 1;
    PMD1bits.T1MD       = 0;
    PMD1bits.PWM1MD     = 0;
    PMD1bits.I2C1MD     = 1;
    PMD1bits.U1MD       = 1;
    PMD1bits.SPI1MD     = 1;
    PMD1bits.AD1MD      = 0;

    //disable Input Capture/Output Compare
    PMD2bits.IC3MD      = 1;
    PMD2bits.IC2MD      = 1;
    PMD2bits.IC1MD      = 1;
    PMD2bits.OC2MD      = 1;
    PMD2bits.OC1MD      = 1;

    //disable comparator and RTCC
    PMD3bits.CMPMD      = 1;
    PMD3bits.RTCCMD     = 1;

    //disable CTMU
    PMD4bits.CTMUMD     = 1;

//PORT CONFIGS
    //disable open drains on Port A, B
    ODCA                = 0x0000;
    ODCB                = 0x0000;

    //Enable AN0 only; digital I/O on all other pins
    AD1PCFGL            = 0x0001;
    TRISA               = 0x0001;   //AN0 must be input for ADC to work right

    //Port B
    TRISB               = 0x0007;   //In on 0,1,2
    LATB                = 0x0000;
    //IFS3bits.FLTA1IF    = 0;        //must be pulled up externally  
    //IFS4bits.FLTB1IF    = 0;

    //Clear outputs
    LATA                = 0x0000;
    //LATB already clear

    //Enable CN4,5,6 (PortB) and corresponding interrupts
    CNEN1bits.CN4IE     = 1;
    CNEN1bits.CN5IE     = 1;
    CNEN1bits.CN6IE     = 1; //pullups are disabled on reset
    IEC1bits.CNIE       = 1; 

    IPC4bits.CNIP       = 0b010; // Change on bus is priority 6 of 7

    //Set UART input to RP8 (17), output ot RP9 (18)
    /*
    RPINR18bits.U1RXR   = 0b01000;
    RPOR4bits.RP9R      = 0b00011;
    */


//TIMER CONFIGS
    //setup Timer1
    T1CONbits.TCS       = 0;        //Use internal clock
    T1CONbits.TCKPS     = 00;       //Prescale 1; ticks at 1.843200MHz
    T1CONbits.TSIDL     = 1;        //Disable during idle
    PR1                 = 46080;    //46080 ticks = 25ms to ovf
    T1CONbits.TGATE     = 0;        //dunno if this should be 0 or 1.
    IPC0bits.T1IP       = 0b001;    //Lowest priority interrupt
    IEC0bits.T1IE       = 1;        //Enable interrupts
    T1CONbits.TON       = 1;        //Turn on

    LATB = 0x0380;
    while(1){
    }
}