User manual

Chapter 4: PowerDAQ Software (SDK)

Method C. Continuous Acquisition using ACB

See SDK Examples Stream2.c

Method C uses the PowerDAQ Advanced Circular Buffer mechanism.

Acquisition runs continuously and each time an event occurs, the

application takes control. You can create separate threads in your

application to run the acquisition process.

Analog input configuration is very similar to Method B, however the

buffer is setup is a different way:

Set up the buffers

• Allocate and register the buffer with the board

# _PdAllocateBuffer(…)

Use as big a buffer as you need. The buffer size is limited

by the amount of memory installed on your PC. You can

specify from two to N frames to use. Frame size (in scans)

notifies the driver when the application wants to receive

eFrameDone events. In the case of two frames per buffer

we’re dealing with the classic double-buffering mechanism.

The larger number of frames makes the operations elastic

and decreases probability of buffer overflow.

• _PdRegisterBuffer(…)

Set dwWrapAround = AIB_BUFFERWRAPPED to use

the circular buffer. The circular buffer mechanism is

explained in Appendix C.

Applications should process events in a different way. Each time it

detects eFrameDone events it means that one or more frames were

filled with data.

Acquisition

• Wait for event notification