Possible Internal ArmStartTrigger Sources for 6602

[ugip]

Hi,

I am using a PCI-6602 card in my application and I am using all 8 counter input channels for counting edges of PWM signals.

Everything works fine except for one thing. It is essential that the counting of all 8 channels starts simultaneously.

I know that I have to use the "ArmStartTrigger" property of the respective channels to achieve that. But I don't know what would be the best "Source" for it.

As the measurement system is already at the customer's site, it will be difficult to change/add hardware. I.e. a software only solution is preferred.

The manual of the 6602 reads: "The Arm Start Trigger may be an internal or external signal".

What internal signals are available on the 6602?

Can any of that internal signals solve my problem?

I know e.g. that a 6250 card can utilize "ai/StartTrigger" as trigger source to synchronize analog input tasks with other tasks. Is there something similar for the 6602?

Regards,

Udo

[Kevin_Price]

If I recall correctly the DIO_0 pin doubles as PFI_0 which can be used as an arm start trigger source.

1. Create a simple on-demand DO task for DO_0.   Write a "F" to it to set it Low.

2. Configure all your counters to use a rising edge on PFI_0 as an Arm Start trigger, and start them.

3. Write a "T" to the DO task to create the rising edge.  (I would then write a "F" before stopping the task.  I just figure it's a good habit to make both edges explicitly so if I decide in the future to react to a falling edge, it's one less thing to have to go back and change.)

-Kevin P

[ugip]

Thank you for the fast reply.

I didn't come to the idea to use a PFI-line as start trigger (which is then an input for the counter tasks) and then write to that PFI-line as digital output. Still sounds strange, but if it works

Just to summarize (in C#, easier to write in a message)

I will configure all counter tasks with PFI0 as ArmStartTrigger (Rising):

TaskPWM1.Triggers.ArmStartTrigger.ConfigureDigitalEdgeTrigger(PWMDev + "PFI0", DigitalEdgeArmStartTriggerEdge.Rising);

TaskPWM2.Triggers.ArmStartTrigger.ConfigureDigitalEdgeTrigger(PWMDev + "PFI0", DigitalEdgeArmStartTriggerEdge.Rising);

:

After starting all counter tasks, they are waiting for the trigger to actually start counting. Now I will do exactly that in a seperate thread:

Task StartTrigger = new Task("StartTrigger");

StartTrigger.DOChannels.CreateChannel(PWMDev + "port0/line0", "", ChannelLineGrouping.OneChannelForEachLine);

DigitalSingleChannelWriter StartTriggerWriter = new DigitalSingleChannelWriter(StartTrigger.Stream);

StartTrigger.Control(TaskAction.Verify);

StartTriggerWriter.WriteSingleSampleSingleLine(true, false);

StartTriggerWriter.WriteSingleSampleSingleLine(true, true);

StartTriggerWriter.WriteSingleSampleSingleLine(true, false);

StartTrigger.Dispose();

StartTrigger = null;

That should work, isn't it? Do you think I need a waiting time in between the 'F', 'T', 'F' writings?

Regards,

Udo

[Kevin_Price · Accepted solution]

The basic idea looks right.  I can't vouch for the syntax on C# calls to DAQmx because I'm strictly a LabVIEW guy, but I don't see anything that looks out of place.  I doubt you need any waiting time during the F-T-F sequence.  The board hardware will be triggering off a transition edge and software calls through the driver to change the digital state will probably each take a few microsec or more.

-Kevin P