I am trying to match an Analog Probe output (NI-9219) to a quadrature encoder position (NI-9411) using FPGA targets. The encoder position is a 16 bit while the probe output is 24 bit. These need to be joined into a FIFO for use in a Host VI. I have found a sample code using the FPGA wizard for the encoder position but I dont know how to "clock" the data aquisition from the probe to the position of the encoder.The end goal is to be able to display the probe reading in relation to the encoder position. I know that the integration time of the 9219 needs to be much larger than that of the 9411 due to the difference in resolution. Any ideas? I attached a block diagram of the rough idea I am trying to accomplish.
If I understand you correctly you are trying to figure out how to grap one sample from each to match together. One solution would be to place the two measurments inside of the same while loop. This would cause that both measurements were taken and placed in the fifo before the next measurements could begin.
You are correct, but the two signals have different integration times, as in it takes longer for the 24 bit signal to be measured than the 16 bit encoder signal. How do you match two signals together when one takes longer to capture than the other?
Obviously the value is changing on both devices during the time of measuring. There is no way to predict with perfect accuracy where the values would truly match. As long as you start the captures at the same time then you are going to be close. If you like you could then adjust one of the values programatically based on your own thoughts and experimentation. Think of it this way ... you can only be as accurate as your least accurate device. Therefore the 24 bit value would have multiple 16-bit values that it could correlate to. One pair of matches would not necessarily be better than another pair of matches. Note: Be aware that when set to High SPeed the 9219 takes 10mS to capture but when set to High Resoltuoin it takes 500 mS.
