Error 50400 on FPGA to Host DMA FIFO

[asper]

I Folk,I am using a DMA FIFO to
transfer data between the target (FPGA, PXI 7813R) and the host
(Windows, PXI-8106, LabView 8.5.1) and when the FIFO is empty I
receive the following error:
    Error - 50400 occurred
at nirio_DMARead.vi:1    Possible reason(s)    The transfer did
not complete within the timeout period or within the specified number
of retries.



I have set:    Number of Elements: 1    Timeout (ms): 0





The Windows routine read
recursively (every 100 ms) the FIFO to get the FPGA analysis results.Because of different
conditions, the FPGA routine write or not data on the DMA FIFO and
can happen that the DMA FIFO is empty.A longer timeout do not
make sans because the FIFO can be empty for a very long while and,
furthermore, no data in a loop time it is a result too.
How can I fix this
problem?




Thanks,Asper

[Chuck_81]

Hi Asper,
the timeout error -50400 you receive from FIFO Read method is expected, because of the parameters you set (timeout = 0) for the given function and the behaviour of the FPGA you described (FIFO write operation happening only in certain conditions).
What I suggest is to filter this error code -50400 by using a simple unbundle function for the error cluster wire and comparing the "code" value with -50400; then you can filter it with the Clear Errors.vi function or changing the error into a warning by negating the "status" element of the error cluster.
Hope this helps,
Fabio 

[asper]

Hi Fabio,the workaround you suggest
is fine.



I have further worked and
have found a different way.First I use a
Read-FPGA-Interface method to read the number of elements available
in the FIFO, followed by a second Read-FPGA-Interface method to
actually read the elements.This approach works fine
if the FIFO is empty too.



The first
Read-FPGA-Interface method is set:    Number of Elements: 0    Timeout (ms): 0



The second
Read-FPGA-Interface method is set:    Number of Elements:
connected to the "Elements Remaining" from the first
Read-FPGA-Interface method    Timeout (ms): 0


Many thanks,Asper