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F28026 - SCI RX FIFO interrupt only receiving every second byte in stream

Harvey Green
Prodigy 20 points

Other Parts Discussed in Thread: TMS320F28026

Hi All,

I'm using the TMS320F28026 piccolo device.

I am receiving serial data via the SCI FIFO RX interrupt, but am seeing the strange behaviour that it receives only every second byte in the data stream.

I've looked at the data with a scope, and it's all there.

The RX FIFO interrupt level is set to SCI_FifoLevel_1_Word  ... so it should interrupt every byte.

baud rate has been set correctly to 31250 - and I'm able to transmit data ok.

Here's my RX interrupt handler function ...

#define RX_BUFFER_SZ  32
unsigned char rx_buffer[RX_BUFFER_SZ];
unsigned char rx_buffer_count;

//
// Receive a character via the SCI interrupt
//
interrupt void sciaRxFifoIsr(void)
{
    uint16_t data = SCI_getData(mySci);

    rx_buffer[rx_buffer_count] = (unsigned char)(data & 0x00FF);
    rx_buffer_count = rx_buffer_count + 1;

    if (rx_buffer_count == RX_BUFFER_SZ) {
        rx_buffer_count = 0;
    }

    // Clear Overflow flag
    SCI_clearRxFifoOvf(mySci);

    // Clear Interrupt flag
    SCI_clearRxFifoInt(mySci);

    // Issue PIE ack
    PIE_clearInt(myPie, PIE_GroupNumber_9);

    return;
}

The byte stream I see on the scope and the one I am expecting is

00 14 0F 9C 80 03 03 00 00 00 00 01 2A 4E 62

The byte stream I receive via the interrupt is

14 9C 03 00 00 01

... which is every second byte of the original stream, and its also short one byte (4E).

Can't work out what could be causing this if anything. Would really appreciate any suggestions or help with this. Have been working on it for a couple of days now without any progress.

Thanks in advance

Harvey

  • 0
    Prodigy 20 points

    FYI, my solution was to use the standard TX and RX interrupts and not use the FIFO.

    I also used the SCIA getData and putData functions to receive/transmit the data one byte at a time.

    I was never able to get the communications working with the FIFO.

  • 0
    Prodigy 30 points

    I'm quite late to reply to this, but hopefully this helps someone else. I found that the code for SCI_setRxFifoIntLevel was broken, and was not setting the bit. So I copied the code from the SCI.c for that function to my code, and it worked!

    The code I replaced "SCI_setRxFifoIntLevel(mySci,SCI_FifoLevel_1_Word);" with was:

    ((SCI_Obj *)mySci)->SCIFFRX &= (~SCI_SCIFFRX_IL_BITS);
((SCI_Obj *)mySci)->SCIFFRX |= SCI_FifoLevel_1_Word;

    This seemed to work for me to get the FIFO interrupt working.