DMA FIFO FPGA in CVI or LabVIEW

[SchamWow]

FPGA Target FIFO is configured for 8197 elements

                NiFpga_MergeStatus(&iFpgaStatus, NiFpga_Open(FPGABitFileName,
                                                             NiFpga_RseriesRIO_Signature,
                                                             Address,
                                                             0,
                                                             &hSession));

               
                NiFpga_MergeStatus(&iFpgaStatus,NiFpga_ConfigureFifo(hSession,
                                        NiFpga_RseriesRIO_HostToTargetFifoU8_DMAFIFO,
                                        3000000));
       
               
NiFpga_WriteFifoU8(hSession,NiFpga_RseriesRIO_HostToTargetFifoU8_DMAFIFO,
  uArray,
  20000,NiFpga_InfiniteTimeout,
  &uEmptyElementsRemaining);

uEmptyElementsRemaining  is 2980000   <----------After above call

NiFpga_WriteFifoU8(hSession,
              NiFpga_RseriesRIO_HostToTargetFifoU8_DMAFIFO,
  uArray,
  20000,NiFpga_InfiniteTimeout,
  &uEmptyElementsRemaining);

               uEmptyElementsRemaining  is 2968197   <----------After above call

[Was expecting 2960000 elements remaining in DMA FIFO after second call]

When the same steps are executed on LABVIEW [with labview equivalents of above functions], it produced different result. i.e. When executed with Labview [with same FPGA FIFO size and DMA fifo size] ,

uEmptyElementsRemaining  was 2980000 and 2960080 after first and second write method.

Also when Labview VI was run continuously, uEmptyElementsRemaining   was changing after the second write method but was correct [2980000] after first write method.

[DylanC]

Hi SchamWow,

Are you calling the NiFpga_StartFifo in the same order in your LabVIEW and CVI code?

NiFpga_StartFifo

NiFpga_Status NiFpga_StartFifo(NiFpga_Session session, uint32_t fifo)

Starts a FIFO.

Parameters

Name	Type	Description
session	NiFpga_Session	handle to a currently open session
fifo	uint32_t	the FIFO to start