Must the buffer pointed in calls to WFM_DB_Tra​nsfer be at the same address?

Question

We have a need to produce a dynamically changing output signal. Double Buffering looked promising to achieve this.
From trial and error it appears that the address pointed to from WFM_Load must be used in WFM_DB_Transfer. We hoped to have multiple buffers and change the output by pointing to the desired buffer in calls to WFM_DB_Transfer. When this was attempted the first buffer change worked but successive buffer changes had no impact and it continued to output the second buffer.
When we copied the desired buffer to a fixed buffer referenced in WFM_Load and WFM_DB_Transfer than all worked as expected. This has led us to conclude that the buffer address must be fixed. This is dissa
ppointing because otherwise unecessary memory copies are taking place.
Is this correct? If so is the same true of the size specified in WFM_DB_Transfer calls. We want the size to be able to vary because the algorithms used to determine the levels needed for the desired frequencies varies the buffer size in an effort to ensure that buffers can transition at the same phase.
Any help would be appreciated,
Jack

Answer 1

Jack;
You are correct on your considerations. Unfortunately, you need to use the same memory position for both Load and Transfer calls. You will need to make the size don't vary and use the same memory area, if you need to change the waveform on the fly.
I'm attaching a CVI code which uses those same function calls to change the waveform output on the fly. You can use that code as future reference.
Hope this helps.
Filipe
Attachments:
DAQ_Generate_Waveform.zip ‏8 KB