c - MicroChip dsPic33, UART RX interrupt is not being called -

good afternoon,

i've configured rx interrupt using following simple function.

char c; void __attribute__((interrupt, no_auto_psv)) _u1rxinterrupt( void )  {      ifs0bits.u1rxif = 0; // clear rx interrupt flag      c = u1rxreg; }  

the problem is, uart transmits fine, interrupt service routine never entered when gets sent character. can trace scope character sent without issues, interrupt not triggered.

the device used communication ttl-232r-3v3. device running @ 3.3v actual model number of dspic33 p33fj128mc802 programming environment mplab 8 , compiled xc16

is there missing setting perhaps enable interrupt? missing?

thanks, here uart initialization code.

u1modebits.uarten = 0;  // bit15 tx, rx disabled, enable @ end of func u1modebits.usidl = 0;   // bit13 continue in idle u1modebits.iren = 0;    // bit12 no ir translation u1modebits.rtsmd = 0;   // bit11 simplex mode u1modebits.uen = 0;     // bits8,9 tx,rx enabled, cts,rts not u1modebits.wake = 0;    // bit7 no wake (since don't sleep here) u1modebits.lpback = 0;  // bit6 no loop u1modebits.abaud = 0;   // bit5 no autobaud (would require sending '55') u1modebits.urxinv = 0;  // bit4 idlestate = 1  (for dspic) u1modebits.brgh = 0;    // bit3 16 clocks per bit period u1modebits.pdsel = 0;   // bits1,2 8bit, no parity u1modebits.stsel = 0;   // bit0 1 stop bit  //  u1brg = (fcy / (16 * baudrate)) - 1 //  u1brg = (36850000 / (16 * 9600)) - 1 //  u1brg = 238.908854 //round 239  u1brg = 239;  u1stabits.utxisel1 = 0; //bit15 int when char transferred (1/2 config!) u1stabits.utxinv = 0;   //bit14 n/a, irda config u1stabits.utxisel0 = 0; //bit13 other half of bit15 u1stabits.utxbrk = 0;   //bit11 disabled u1stabits.utxen = 0;    //bit10 tx pins controlled periph u1stabits.utxbf = 0;    //bit9 *read bit* u1stabits.trmt = 0; //bit8 *read bit* u1stabits.urxisel = 0;  //bits6,7 int. on character recieved u1stabits.adden = 0;    //bit5 address detect disabled u1stabits.ridle = 0;    //bit4 *read bit* u1stabits.perr = 0;     //bit3 *read bit* u1stabits.ferr = 0;     //bit2 *read bit* u1stabits.oerr = 0;     //bit1 *read bit* u1stabits.urxda = 0;    //bit0 *read bit*  rpinr18bits.u1rxr = 0b00010;//7; //rx pin rp2 rpor1bits.rp3r = 0b00011;   //tx pin rp3  u1modebits.uarten = 1;  // , turn peripheral on u1stabits.utxen = 1; 

check if pin has additional functionality. typically ad (analog pin). make sure turn off analog, via adp or ansel registers (type , number varies depending on exact chip) e.g. have routine (i use both 33f , 33e , high , low pincount 1 of both, hence ifdefs)

void analogoff(void){ #if defined(__dspic33f__)     adpcfg  =0xffff;     ad1pcfgh=0xffff;     ad1pcfgl=0xffff; #endif #if defined(__dspic33e__) #if !defined(__dspic33ep256mu806__)     ansela=0; #endif     anselb=0;     anselc=0;     anseld=0;     ansele=0;      anselg=0; #endif } 

also, make absolutely sure oscillator , part's speed correct, though if tx has correct baudrate (scope!) ok.

my uart1 init:

u1brg  = brgval; u1mode = 0x8000;        // reset uart 8-n-1, alt pins, , enable lowspeed (=bit 3) u1modebits.usidl =0;    // disable module when device idle. u1modebits.iren  =0;    // irda disable u1modebits.rtsmd =0;    // flow control mode (1= simplex mode) u1modebits.uen   =0;    // rts en cts controlled portlatches u1modebits.wake  =0;    // no wakeup enabled; u1modebits.lpback=0;    // loopback disabled u1modebits.abaud =0;    // no autobaud #if !defined(__pic24f__) u1modebits.urxinv =0;   // rxinv inversion rx. (0= idle = '1') #endif u1modebits.brgh  =1;    // high speed. u1modebits.pdsel =0;    // 8 bit no parity u1modebits.stsel =0;    // 1 stopbit.                   u1sta  = 0x0440;  u1stabits.urxisel0=0;// reset status register , enable tx & rx.  u1stabits.urxisel1=0;   // rx interrupt on char.  _u1rxif=0;               // clear uart rx interrupt flag _u1rxie = 1;             // interruption active pour la reception _u1rxip=2; _u1txip=2; _u1txif=0; _u1txie=0;             // enabled when sending u1modebits.uarten=1;