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Altera_Forum's avatar
Altera_Forum
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15 years ago

DMA transfer inside ISR: Problem

Hi everybody, I think this is a common issue, but I didn't find a solution to my question, so hopefully I will get an answer here: I have a DMA controller which I want to use on an IRQ com...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
15 years ago

Hi,

I hope this will help you. But I am using an ISR for servicing a completed DMA-Transfer. 

Int32 Transmit(Char8 * pTx, Int32 lLength)
{
    //softwarereset
    IOWR_ALTERA_AVALON_DMA_CONTROL(DMA_RS485_BASE, 0x1000);
    IOWR_ALTERA_AVALON_DMA_CONTROL(DMA_RS485_BASE, 0x1000);
    IOWR_ALTERA_AVALON_PIO_DATA    (PIO_RS485_BASE,TRANSMIT); // setting the direction of the transceiver using a PIO
    IORD_ALTERA_AVALON_UART_RXDATA(UART_RS485_BASE); //dummy read to UART
    IOWR_ALTERA_AVALON_DMA_CONTROL(DMA_RS485_BASE,
                                             ALTERA_AVALON_DMA_CONTROL_WCON_MSK|
                                             ALTERA_AVALON_DMA_CONTROL_BYTE_MSK|
                                             ALTERA_AVALON_DMA_CONTROL_LEEN_MSK|
                                             ALTERA_AVALON_DMA_CONTROL_I_EN_MSK); //setzen von WCON
    DmaTransfer                              ((Int32) IOADDR_ALTERA_AVALON_UART_TXDATA(UART_RS485_BASE),
                                            (Int32) pTx, lLength);
    return 0;
}
Int32 Receive(Char8 * pRx, Int32 lLength)
{
    while (!(IORD_ALTERA_AVALON_UART_STATUS(UART_RS485_BASE)
                & ALTERA_AVALON_UART_STATUS_TMT_MSK));
    //softwarereset
    IOWR_ALTERA_AVALON_DMA_CONTROL(DMA_RS485_BASE, 0x1000);
    IOWR_ALTERA_AVALON_DMA_CONTROL(DMA_RS485_BASE, 0x1000);
    IORD_ALTERA_AVALON_UART_RXDATA(UART_RS485_BASE); // dummy read to UART
    IOWR_ALTERA_AVALON_DMA_CONTROL(DMA_RS485_BASE,
                                             ALTERA_AVALON_DMA_CONTROL_RCON_MSK|
                                             ALTERA_AVALON_DMA_CONTROL_BYTE_MSK|
                                             ALTERA_AVALON_DMA_CONTROL_LEEN_MSK|
                                             ALTERA_AVALON_DMA_CONTROL_I_EN_MSK);
    IOWR_ALTERA_AVALON_PIO_DATA    (PIO_RS485_BASE,RECEIVE); // setting the direction of the transceiver using a PIO
    DmaTransfer                            ((Int32)pRx,
                                             (Int32)IOADDR_ALTERA_AVALON_UART_RXDATA(UART_RS485_BASE),
                                             lLength);
    return 0;
}
void DmaTransfer(Int32 lWhere, Int32 lFrom, Int32 lHowMuch)
{
    while ((IORD_ALTERA_AVALON_DMA_STATUS(DMA_RS485_BASE)
             & ALTERA_AVALON_DMA_STATUS_BUSY_MSK));
    IOWR_ALTERA_AVALON_DMA_STATUS        (DMA_RS485_BASE, 0);
    IOWR_ALTERA_AVALON_DMA_RADDRESS    (DMA_RS485_BASE,(Int32) lFrom);
    IOWR_ALTERA_AVALON_DMA_WADDRESS    (DMA_RS485_BASE,(Int32) lWhere);
    IOWR_ALTERA_AVALON_DMA_LENGTH        (DMA_RS485_BASE, lHowMuch);
    IOWR_ALTERA_AVALON_DMA_CONTROL    (DMA_RS485_BASE,
                                                 ALTERA_AVALON_DMA_CONTROL_GO_MSK |
                                                 IORD_ALTERA_AVALON_DMA_CONTROL(DMA_RS485_BASE));
}
Good luck!