cDAQ Buffered Counter Acquisition

[jgcode]

[cross-post to ni.com]

Hi

I am trying to setup a buffered counter acqusition (correlated) using compact DAQ.

Hardware: cDAQ 9172 chassis

Slot 1: NI 9237 (AI Bridge used as an external timing source only)

Slot 5: NI 9411 (High Speed DI TTL)

I have to use the extra module to export it's clock as I am using the internal counters in slot 5.

1) Is this hardware compatiable?

2) If so, any suggestions on how to get this to work as I am having trouble running it.

I use the following parameters which works fine for an On-Demand sampling - it reads back the expected value from the sensor.

But when I switch to Continuous the I get a timeout error.

However, if I use simulated hardware through MAX I don't get an error and the buffer fills on the screen.

Any ideas?

Regards

JG

[Anu Kalidas]

While using the real hardware, don't you have to set the sampling rate for the 9237 module? Not sure whether without this the ai sample clock will generate pulses. It looks like the acquisition timed out before any sample is acquired. A quick check can be to replace 'cDAQ1Mod1/ai/SampleClock' with 'cDAQ1Mod1/ai/SampleClockTimebase'...

[jgcode]

QUOTE (Kal @ Apr 3 2009, 07:00 PM)

A quick check can be to replace 'cDAQ1Mod1/ai/SampleClock' with 'cDAQ1Mod1/ai/SampleClockTimebase'...

Unfortunately both gave the same results.

Cheers

JG

[Anu Kalidas]

QUOTE (jgcode @ Apr 3 2009, 05:34 PM)

Unfortunately both gave the same results.

Cheers

JG

In one of the example VIs they say that you cannot use internal timebases for clock and should be supplied 'externally'. I guess this means you will have to give the clock signal to one of the PFI lines of 9411. Internal routing (which is the case when you use cDAQ1/ai/SampleClock) may not be supported.

[jgcode]

QUOTE (Kal @ Apr 4 2009, 04:17 PM)

In one of the example VIs they say that you cannot use internal timebases for clock and should be supplied 'externally'. I guess this means you will have to give the clock signal to one of the PFI lines of 9411. Internal routing (which is the case when you use cDAQ1/ai/SampleClock) may not be supported.

Thanks Kal. I was told by NI Support that this configuration is correctly setup to use an external timing source - i.e. the clock is supplied by the NI 9237 module.

Are you saying this is not an external clock?

[Anu Kalidas]

QUOTE (jgcode @ Apr 4 2009, 12:20 PM)

Thanks Kal. I was told by NI Support that this configuration is correctly setup to use an external timing source - i.e. the clock is supplied by the NI 9237 module.

Are you saying this is not an external clock?

JG,

My cDAQ knowledge is very limited, so it is possible that what NI support says is correct.

Till now, I was of the thinking that the cDAQ chassis provides all timing (clocks) to IO modules. Hence I assumed that the ai/SampleClock or timebase is an internal source and not an external source.

One thing I am not sure is, when we specify ai/sampleclock as the clock source, how will it get routed to the 9411 module? There is a direct route between sample clock and mod5 PFI lines, but will NI-DAQ do the routing or do you have to route the clock to a PFI line and then use that PFI line as clock for the position task?