I am using a pic for modbus communications and everything works except the mpg. I feed the tickcount and mpg1 count with the following interrupt code:

defs


   INTCON2bits.INTEDG1 = 0;  //Interrupt on falling edge (INT1)
     INTCON3bits.INT1IP = 1;   //INT1 External Interrupt Priority bit (Set to High)
     INTCON3bits.INT1IF = 0;   //Clear interrupt flag bit
     INTCON3bits.INT1IE = 1;   //Enable the INT1 external interrupt
 
   INTCON2bits.INTEDG2 = 0;  //Interrupt on falling edge (INT2)
     INTCON3bits.INT2IP = 1;   //INT2 External Interrupt Priority bit (Set to High)
     INTCON3bits.INT2IF = 0;   //Clear interrupt flag bit
     INTCON3bits.INT2IE = 1;   //Enable the INT2 external interrupt

     RCONbits.IPEN = 1;    //Enable priority levels on interrupts
    INTCONbits.GIEH = 1; // Enables all unmasked interrupts
   INTCONbits.GIEL = 1; // Enables all unmasked peripheral interrupts



then int code itself
void
handle_high_isr(
  void
) {

   if (INTCON3bits.INT1IF)
    {
      INTCON3bits.INT1IE = 0;
        mpg_count++;
      mpg_tickcount = (unsigned char) ReadTimer0();
      WriteTimer0( 0 );
       INTCON3bits.INT1IF = 0; // clear int flag
      INTCON3bits.INT1IE = 1;
    }

   if (INTCON3bits.INT2IF)
    {
      INTCON3bits.INT2IE = 0;
      mpg_count--;
      mpg_tickcount = (unsigned char) ReadTimer0();
      WriteTimer0( 0 );
       INTCON3bits.INT2IF = 0; // clear int flag
      INTCON3bits.INT2IE = 1;
    }
   // Handle any pending USB tasks
   USBDeviceTasks();
}

If I spin the mpg quickly it always just registers the last movement + or -. If I move it slowly it appears to register movement at random. It is always in the right direction but may not register no matter how slow.

Any ideas?