F28027 troubles with keypad interrupt

Hello!

I have C2000 Piccolo LAUNCHXL-F28027 and 4x4 matrix keypad, so I want to connect keypad to the F28027 using GPIO pins but get problems:

1. My counter variable increases by several points after one key interruption(e.g. before one interruption = 0, after one interruption = 3).
2. Sometimes interruptions occurs when I release the key(but I have set "XIntruptRegs.XINT1CR.bit.POLARITY = 2").
3. Sometimes interruptions occurs when I press keys which don't have interruptions.

Here is the code:

#include "DSP28x_Project.h"     // Device Headerfile and Examples Include File

void delay_loop(unsigned long i);
void Gpio_select(void);

interrupt void xint1_isr(void);
int counter;
void main(void)
{
	counter = 0;

	 InitSysCtrl();

	 DINT;

	 InitPieCtrl();

	 IER = 0x0000;
	 IFR = 0x0000;


	 InitPieVectTable();


	 EALLOW;
	 PieVectTable.XINT1 = &xint1_isr;
	 EDIS;


	 PieCtrlRegs.PIECTRL.bit.ENPIE = 1;
	 PieCtrlRegs.PIEIER1.bit.INTx4= 1;

	 IER |= M_INT1;
	 EINT;



	 EALLOW;
	 GpioCtrlRegs.GPAMUX1.bit.GPIO1 = 0;
	 GpioCtrlRegs.GPAPUD.all = 0;
	 GpioCtrlRegs.GPADIR.bit.GPIO1 = 1;
	 EDIS;



	 EALLOW;
	 GpioCtrlRegs.GPAMUX1.bit.GPIO2 = 0;
	 GpioCtrlRegs.GPAPUD.bit.GPIO2 = 0;
	 GpioCtrlRegs.GPADIR.bit.GPIO2 = 0;
	 GpioCtrlRegs.GPAQSEL1.bit.GPIO2 = 2;
	 GpioCtrlRegs.GPACTRL.bit.QUALPRD2 = 0xFF;
	 EDIS;


	 EALLOW;
	 GpioIntRegs.GPIOXINT1SEL.bit.GPIOSEL = 2;
	 EDIS;

	 XIntruptRegs.XINT1CR.bit.POLARITY = 2;

	 XIntruptRegs.XINT1CR.bit.ENABLE = 1;


	 while(1)
	 {

	 }
}


interrupt void xint1_isr(void)
{
	 PieCtrlRegs.PIEACK.all = PIEACK_GROUP1;
	 counter++;
}

How can I fix these problems?