ISR driven UART is missing characters (even at 9600bps... same prob at 230400)

Any ideas on what I'm missing here that is causing me to miss characters?

I'm interfacing to a device that shoots out RS232 packets (up to 200 per second if the bps can handle itI can select the BPS, but it is always N-8-1). Right now, I have the device running (and the UART) at 9600bps and locked to 5 packets per second... although, this problem happens at 115200, 230400, and is terrible at 460800bps(which is where I need to get).

The UART seems to be missing characters, especially towards the end of the 'packets' which are around 100bytes in length. towards the front of the packet I seem to get everything and towards the 'rear' it starts to miss them... the 'ISR' itself generally takes 500ns to execute, but that doesn't include the call latency... but I can't see that being a problem at 9600bps... Also the ring-buffer is 4k in size. I have set a breakpoint so that I can debug after it gets 1024 characters and the ring-buffer is missing them... so it can't be a wrapping/overflow problem.... grrrr.

Here's how I'm setting up my code in main to test this problem:

alt_irq_init (ALT_IRQ_BASE);

alt_sys_init();

unsigned char ch;

unsigned int baudrate=9600;

UsartInit(baudrate);

UsartInit_2(baudrate);

//register the ISR handler for UART 0)

alt_ic_isr_register(UART0_IRQ_INTERRUPT_CONTROLLER_ID,

UART0_IRQ,

IsrUsart,0,0);

//register the ISR handler for UART 1

alt_ic_isr_register(UART1_IRQ_INTERRUPT_CONTROLLER_ID,

UART1_IRQ,

IsrUsart_2,0,0);

//enable Interrupts for UART 0

alt_ic_irq_enable(UART0_IRQ_INTERRUPT_CONTROLLER_ID,

UART0_IRQ);

//enable Interrupts for UART 1

alt_ic_irq_enable(UART1_IRQ_INTERRUPT_CONTROLLER_ID,

UART1_IRQ);

There there's the big 'while(1)'in main():

while (1)

{ //update heartbeat on JP5 header

jp5tracker ^= 0x01;//D0 on L.A.

IOWR_ALTERA_AVALON_PIO_DATA(JP5_BASE, jp5tracker);

while(!UsartIsEmpty_2())

{ //toggle LEDG1 when characters are processed from VN100 plugged into the HSMC-ICB

greenLEDtracker ^= 0x02;

IOWR_ALTERA_AVALON_PIO_DATA ( GLED_BASE , greenLEDtracker );

ch=GetUsart_2();

jp5tracker ^= 0x02;//D1 on L.A.

IOWR_ALTERA_AVALON_PIO_DATA(JP5_BASE, jp5tracker);

i++;//counter to set a breakpoint with

}

here's the ISR handler and some helpers for the ring buffer.

void UsartInit_2(unsigned int BaudRate_2)

{

unsigned int divisor_2;

divisor_2 = (ALT_CPU_FREQ/BaudRate_2)+1;

IOWR_ALTERA_AVALON_UART_DIVISOR(UART1_BASE, divisor_2);

IOWR_ALTERA_AVALON_UART_CONTROL(UART1_BASE, ALTERA_AVALON_UART_CONTROL_RRDY_MSK);

}

void IsrUsart_2(void* context_2, unsigned int id_2)

{

IOWR_ALTERA_AVALON_PIO_DATA(JP5_BASE, 0xFF);//inserted to time/track this routine

//grab data byte and save it

USART_RX_buffer_2[USART_RX_hd_2++] = IORD_ALTERA_AVALON_UART_RXDATA(UART1_BASE);

//move/wrap buffer pointer

if (USART_RX_buffer_2 == '*')

z_2==1;

if (USART_RX_hd_2 == USART_BUFFER_SIZE_2) USART_RX_hd_2 = 0;

USART_RX_full_2 = (USART_RX_hd_2==USART_RX_tl_2);

IOWR_ALTERA_AVALON_PIO_DATA(JP5_BASE, 0x00);//inserted to time/track this routine

}

unsigned char UsartIsEmpty_2()

{

return ((!USART_RX_full_2) && (USART_RX_hd_2==USART_RX_tl_2));

}

//this grabs a single character from the RX circular buffer.

unsigned char GetUsart_2(void)

{

unsigned char rxChar_2;

//should never call this w/o checkign status, but it may happen. this keeps

//the ring buffer sane during that sort of abuse.

if (((!USART_RX_full_2) && (USART_RX_hd_2==USART_RX_tl_2)))

return 0x00;

else

{

rxChar_2=USART_RX_buffer_2[USART_RX_tl_2++];

if (USART_RX_tl_2 == (USART_BUFFER_SIZE_2))

USART_RX_tl_2=0;

USART_RX_full_2=0;

return rxChar_2;

}

}

Anyway... if I write some debug code on a PC to send data... as long as I insert some 'sleeps' in it between characters... never misses a character... Also, I can watch the ISR's debug 'flip' of JP5 and the ISR does get called, and the circular buffer does get populated... it is just missing characters. I have verified (with a PC's serial port) that the packets are being sent properly and contain all the data.

Here's what I'm using:

DE2-115 development board(cyclone IV) with HSMC-ICB (Altera's INK)

Quartus13.0 SP1 with EDS, the UART is:

UART (RS-232 Serial Port)

Name altera_avalon_uart

Version 13.0.1.99.2

Some BSP settings:

enable_small_c_library-'checked'.... 'nocheck' for enable_gprof, enable_reduced_device_drivers, or enable_sim_optimize

'none' for sys_clk_timer, and timestamp_timer