Problem in reading data from GPS

[kulks]

Hi,
I'm interfacing a skynav skm53 GPS with an ARM cortex LPC1768 microcontroller on board MCB1700. Here's the small code snippet for initialization of UART
and reading GPS data. I can see the characters coming in but I don't get them in desired sequence i.e NMEA format (starting $GPGGA).

Please let me know if there is anything wrong in my code.

uint32_t UARTInit( uint32_t PortNum, uint32_t baudrate )
{
uint32_t Fdiv;
uint32_t pclkdiv, pclk;

LPC_PINCON->PINSEL4 &= ~0x0000000F;
LPC_PINCON->PINSEL4 |= 0x0000000A; /* Enable RxD1 P2.1, TxD1 P2.0 */


if(PortNum == 1 )
/* By default, the PCLKSELx value is zero, thus, the PCLK for
all the peripherals is 1/4 of the SystemFrequency. */
/* Bit 8,9 are for UART1 */
pclkdiv = (LPC_SC->PCLKSEL0 >> 8) & 0x03;
switch ( pclkdiv )
{
case 0x00:
default:
pclk = SystemFrequency/4;
break;
case 0x01:
pclk = SystemFrequency;
break;
case 0x02:
pclk = SystemFrequency/2;
break;
case 0x03:
pclk = SystemFrequency/8;
break;
}

LPC_UART1->LCR = 0x83; /* 8 bits, no Parity, 1 Stop bit */
Fdiv = ( pclk / 16 ) / baudrate ; /*baud rate */
LPC_UART1->DLM = Fdiv / 256;
LPC_UART1->DLL = Fdiv % 256;
LPC_UART1->LCR = 0x03; /* DLAB = 0 */
LPC_UART1->FCR = 0x07; /* Enable and reset TX and RX FIFO. */

NVIC_EnableIRQ(UART1_IRQn);

LPC_UART1->IER = IER_RBR | IER_THRE | IER_RLS; /* Enable UART1 interrupt */
return (TRUE);
}
return( FALSE );



main.c

int main (void){

/* SystemClockUpdate() updates the SystemFrequency variable */
SystemClockUpdate();
UARTInit(1, 9600); /* baud rate setting */

GLCD_Init(); /* Initialize graphical LCD */

GLCD_Clear(White); /* Clear graphical LCD display */
GLCD_SetBackColor(White);
GLCD_SetTextColor(Blue);

while (1)
{


for(UART1Count=0;UART1Count<200;UART1Count++)
{
if((LPC_UART1->RBR) != '\0')
{
UART1Buffer[UART1Count] = LPC_UART1->RBR ; // IRQ handler is not getting invoked, that's why tried to read characters from RBR
// and found some characters too though not in NMEA format
}
}
for(UART1Count=0;UART1Count<200;UART1Count++)
{
if(UART1Buffer[UART1Count] == '$')
{
UART1Count = UART1Count + 1;
if(UART1Buffer[UART1Count] == 'G')
{
UART1Count = UART1Count + 1;
if(UART1Buffer[UART1Count] == 'P')
{
UART1Count = UART1Count + 1;
if(UART1Buffer[UART1Count] == 'G')
{
UART1Count = UART1Count + 1;
if(UART1Buffer[UART1Count] == 'G')
{
UART1Count = UART1Count + 1;
if(UART1Buffer[UART1Count] == 'A')
{
GLCD_DisplayString(Line2,"Hello World!"); // didn't reach here
}
else continue
}
else continue;
}
else continue;
}
else continue;
}
else continue;
}
}

}
}

IRQ_Handler (Not getting Invoked)

void UART1_IRQHandler (void)
{
uint8_t IIRValue, LSRValue;
uint8_t Dummy = Dummy;

IIRValue = LPC_UART1->IIR;

IIRValue >>= 1; /* skip pending bit in IIR */
IIRValue &= 0x07; /* check bit 1~3, interrupt identification */
if ( IIRValue == IIR_RLS ) /* Receive Line Status */
{
LSRValue = LPC_UART1->LSR;
/* Receive Line Status */
if ( LSRValue & (LSR_OE|LSR_PE|LSR_FE|LSR_RXFE|LSR_BI) )
{
/* There are errors or break interrupt */
/* Read LSR will clear the interrupt */
UART1Status = LSRValue;
Dummy = LPC_UART1->RBR; /* Dummy read on RX to clear
interrupt, then bail out */
return;
}
if ( LSRValue & LSR_RDR ) /* Receive Data Ready */
{
/* If no error on RLS, normal ready, save into the data buffer. */
/* Note: read RBR will clear the interrupt */
UART1Buffer[UART1Count] = LPC_UART1->RBR;
UART1Count++;
if ( UART1Count == BUFSIZE )
{
UART1Count = 0; /* buffer overflow */
}
}
}
else if ( IIRValue == IIR_RDA ) /* Receive Data Available */
{
/* Receive Data Available */
UART1Buffer[UART1Count] = LPC_UART1->RBR;
UART1Count++;
if ( UART1Count == BUFSIZE )
{
UART1Count = 0; /* buffer overflow */
}
}
else if ( IIRValue == IIR_CTI ) /* Character timeout indicator */
{
/* Character Time-out indicator */
UART1Status |= 0x100; /* Bit 9 as the CTI error */
}
else if ( IIRValue == IIR_THRE ) /* THRE, transmit holding register empty */
{
/* THRE interrupt */
LSRValue = LPC_UART1->LSR; /* Check status in the LSR to see if
valid data in U0THR or not */
if ( LSRValue & LSR_THRE )
{
UART1TxEmpty = 1;
}
else
{
UART1TxEmpty = 0;
}
}

}

Please help.