Hi Peter, I have a question about the Rt Fifos. I aquire with my Card 6 Analog Voltage values and 3 digital inputs. Fot both I have a Sample clock Frequency of 1Mhz, for both analog and digital input. For my time crital loop I have a dt of 20 ms, which means that for every loop I should get 20000 samples from each channel. With the DAQmx Analog 2D DBL Nchannels Nsamples I should get a 2D array of 6 cahnnels x 20000 samples. The same is also with my digital inputs, but for this a have a 1D array, because I selected one channel for all lines . When I looked how big both arrays were, I was surprised because instead of beeing 20000 samples, the array number always changed. Always bigger that 20000. And also for both digital and anlog differently. I thought I might happen, because at my DAQmx I put a number of -1 for number of samples, which means that it reads the complete buffer. But why is there a difference between the digital and analog amount of samples? The programm is made to simultaniously aquire both digital and analog inputs.
Nest question I have: After the aquisition the data is transfered to a shared variable with a RT fIfo with 2000 elements. Because I read that a RT Fifo cann't be a 2D array, I split the 2D array in 1D array, and made so for every channel a shared variable. What means if I have a RT Fifo of 2000 elements? If I have aquired 25000 samples, means that the samples are saved in blocks of 2000 elements, so in this case I would get 12 blocks with 2000 elements and one block with 1000 elements? Is it right?? What happens when I have different amount of samples for the digital and analog inputs? My analog input are coded with the 3 digital inputs. That means that reading my digital values which can be 0 till 7, the values which I get at analog channel 0 comes from 8 diffent stages. So evreything has to be simultanious. If not than I can not assign the right value to the right status.
I also was quite surprised, because I when I aquire samples from all 6 analog channels and split them to get a 1D array for each channel, sometimes later during aquisition the channel switch. So instead of presenting me ch0 I see ch1 and instead of ch1, ch2 and so on!! And in the Fifo ist the same is also saved! And that fatal for my assigment Has someone already had similar problems?? here is also my new vi! I know it not advised to display data in the time crital loop, but I just wanted to see my raw data, before puting it in the fifo. One more question: What is better to use, a RT Fifo or a shared variable with an RT FIFO. I couldn't find any difference!
Best regards, Elh
