S series DMA

Question

Hi,
I try to use PCI-6143 card under Qnx. I download  DDK files. In the driver of the PCI 6143 , polling read implementation has been done. but i want to use DMA.
For this purpose, i add following function to the shipping polling read example.When i debugging, all functions return kNoError  status but when i try to read i see no data.
Please help, what's wrong
 tDMAError status = kNoError;  
    // Specify DMA and user buffer sizes
    const u32 dmaSizeInSamples = 100;
    const u32 dmaSizeInBytes   = dmaSizeInSamples * sizeof(i32);
    const u32 userSizeInSamples = 10;
    const u32 userSizeInBytes   = userSizeInSamples * sizeof(i32);
    // DMA objects
    tAddressSpace bar0;
    tMITE       *mite;
    tDMAChannel *dma;
    bar0 = bus->createAddressSpace(kPCI_BAR0);
    mite = new tMITE(bar0);
    mite->setAddressOffset(0x600);  
    dma = new tDMAChannel(bus, mite);
    // Configure DMA on the device  
    board->ScarabDMASelect.set(tSSeries::tScarabDMASelect::kChannel1);
    board->ScarabDMASelect.flush ();
    // Configure and start DMA Channel
    status = dma->config (0, tDMAChannel::kRing, tDMAChannel::kIn, dmaSizeInBytes, tDMAChannel::k32bit);
     if (status != kNoError)
         printf ("Error: dma configuration (%d)\n", status);
    status = dma->start();
     if ( kNoError != status )
         printf ("Error: dma start (%d)\n", status);
     else
         // No error - arm and start AI engine
        aiArm(theSTC); 
     aiStart(theSTC); // start acqusition
    // DMA Read

Answer 1

Hi eesen-
The ScarabDMASelect() bitfield is used to determine which DMA channel to use while downloading the large scarab image on scarab-based boards.  It does not apply to AI operations.  The AIAO_select bitfield is indeed the correct entry to indicate the AI DMA channel in use.  Possible values for AIAO_select are as follow (from the E Series RLP manual):
AI AO Select Register
The AI AO Select Register contains 8 bits that control the logical DMA selection for the
analog input and analog output resources. The contents of this register are cleared upon power
up and after a reset condition.
<...>
3–0 Input <D..A> Analog Input Logical Channel D through A—These four
bits select the logical channels to be used by the analog
input. You can only set one of these bits at a time.
In order to achieve a circular buffered DMA operation you should use Ring mode; it is the easiest to work with and works well with the MHDDK DMA library.  I don't have an example specific to the 6143, but the M Series example should be quite similar in terms of the steps to setup buffers and the actual access into the MHDDK DMA library.  Check out aiex3 from the M Series DDK as an example.
Hopefully this helps
Tom W
National Instruments