High Speed Timers

Question

Hi

I'm developping an Data Aquisition Program, to read a bunch of digital sensors.

My problem: the main module, needs to read 32 sensors (I can read a byte at once, so It can be done in 4 steps) in a timebase of about 0,3 to 0,7 ms (miliseconds).

Can it be done in VB.Net Express ? I already saw a post to a 10 ms timer, still ... it takes too long to read all the entries from the Digital Aquisition Board.

Note: the Board is an Advantech PCI-1756 (32 I/O channels), and it has 2 entries that can generate an interrupt if 1 is present. Still, my problem is how to handle the information at such High Speed.

Thank you for your time, and sugestions ...

Best Regards

 

Marco

Answer 1

I would contact Advantech and see if they have a Software Developer's Kit available.  I would think that would be the first place to start and then if they have some dll's etc. that you can work with, you may be able to poll the I/O channels fast enough in VB.

james

aka:Trucker

 

Answer 2

Assuming the board can actually sample at that rate (it doesn't say how fast it is capable of obtaining data - opto isolator rates mean nothing), as trucker says, the SDK will help. You should have something on the CD.

Here's what I would do: write a small C dll which talks to the board and puts the samples into a circular buffer to be read at will, or into a dual buffer with a flag indicating which buffer is available to your program. The buffer size depends on what you are ultimately going to do with the data, and whether your program will use it's own buffer. A HMI response rate needs around 30-40mS, so if you are acquiring at 300uS, your buffer size needs to be at least 200 samples (I'd probably go to about 2000 sample buffer size, perhaps more for such a fast sample rate).