Hi
I have an application where I want to use some sort of hardware timing
to call a function in C# to calculate feedback gains and send a signal
back to the DAQ to control an actuator. The board I bought for this
application was the USB-6211 but subsequently realised that that I
can't use a "SampleComplete" or "SampleClock" event because of it's USB
interface. I found a 6024E card that we had and managed to get
"SampleComplete" event to work, however I am struggling to read data in
the "SampleCompleteEvent" function at any frequency above 1 hz. I
suspect that I may be doing something incorrect in the way I read the
data. Some of the code (for a 6024E card) I have written follows, as
this may explain what I am trying to do a bit better:
{
// Setup the channel:
AI0_Task.AIChannels.
CreateVoltageChannel(("Dev2/ai0"), null, AITerminalConfiguration.Rse,
USB_6211.AI0_InputRange[0], USB_6211.AI0_InputRange[1], A0VoltageUnits.Volts);
// Setup the sample clock:
double f_s = 1000;
AI0_Task.Timing.ConfigureSampleClock(null, f_s, SampleClockActiveEdge.Rising,
SampleQuantityMode.HardwareTimedSinglePoint, 1);
// Setup the reader
AI0_Data = new AnalogSingleChannelReader(AI0_Task.Stream);
// Setup the control loop function:
AI0_Task.SampleComplete += new SampleCompleteEventHandler(ControlLoopFunction);
}
// Control loop function:
private void ControlLoopFunction(object sender, SampleCompleteEventArgs e)
{
AI0_Data = AI0_Data.ReadSingleSample();
// + More control algorithms
}
Everything
works fine, but if I set "f_s" to anything above 1 hz, it doesn't seem
to read data using "AI0_Data = AI0_Data.ReadSingleSample();", the
application just freezes. I suspect that maybe this is not the way to
get data off the card when using a "hardware timed single point" sample
quantity mode, but can't find any other way of getting the data off the
card in my control loop function. So my question is; "How do you
suggest I get a single data point off the card in the control loop
function?".
A subsequent question I have is: "Is it possible to use one of the
counters on a USB-6211 card to time a control loop?". This would be
better as we actually bought the 6211 card for the application in mind.
However if this is not possible, we can use the 6024E card. I should also state the the control loop does not have to be very fast. The speed I have in mind is between 100 and 200 hz.
Thank you for your help
