What mean this error : ' Insufficient DMA Channels available' exactly ?

[Danteei]

Hello,

I have a problem with a VI for send and receive requests.

I have a Compact RIO 9022 with a 9870 module, who permit to connect my host computer to four boxs of gauges (who can give me a pressure).

For that, I have create a FPGA target, because, I don't know why but 9870 module can be added to a project only with it. After that, I have create a VI in the FPGA target with two FIFO (named READ_FIFO and WRITE_FIFO) for send and receive requests. I think this VI is good because I have use a VI find in this site to create this.

But, when I compile the code of this VI, I have a error who say : "There are insufficient DMA channels available on the current target.

                                                                                                   Resource : READ_FIFO (Write Interface).

                                                                                                   Resource : WRITE_FIFO (Read Interface)."

So what's the DMA Channels exactly ? And how can I correct this error ?

I add the two VI's what I use if they can help you.

Thank for your help and sorry for misspelled in this post (English is not my native language).

[Danteei · Accepted solution]

I have find how correct the error,

I have just delete the WRITE_FIFO and replace it by a unsigned 8 bits array in the FPGA.vi and by a method in the (RT)_Test_Module_8.vi. So, the string write in the array and send request via the FPGA.vi to the box of gauge.

I don't know why that work now exactly but if this can help someone, it's a good thing.

++.

[speleato]

Hello Danteei,

Just a quick question, are you using any modules in Scan Mode.  That is, where the modules are added under the chassis and the IO is accessed from RT using variables?  If so, that will use two of the three available DMA channels, which explains the resource error you saw.

If that is the case, another work around would be to move all your modules to the FPGA and do the IO from the FPGA VI.

Sebastian

[Danteei]

Hello speleato,

Yes others modules works in Scan Mode (three 9425, three 9478 and one 9485), and actually I use just one of them to receive information since plate switch in a VI not place in the FPGA target. And this VI send variable to the host computer. So, actually the FPGA.vi work correctly, but if the error come back, I would use your solution by placing modules in the FPGA target.

Thank for your answer.