Newbie: 6020E (USB) slow performance with mixed digital and analog input

[Peter D'Hoye]

Hi,

I'm using a 6020E to do analog and digital input, and I'm getting very bad performance.
Please note that doing IO in Labview is new to me!

I have read the post about 6020E slow performance, and it says I should do buffered IO.
Can anybody point me to some DOC or SAMPLE that actually shows or explains how one should do this. I need to read several digital IO lines (which I can combine in one port-read), and several analog inputs.

Seeing how slow the reading on the 6020E is, I am amazed there is only one post that deals with this issue.
I would be satisfied to get the 6020E into some sort of continuous read mode so that whenever I need data, I get the latest reading right away.


thanks,
Peter D'Hoye

[Peter D'Hoye]

Is buffered capturing possible on a 6020E? All the examples (in the NI Example Finder) that mention buffered acquiring do not list the 6020E....

My favorite would have been the 'Continuous CDI with AI (E).vi' which does analog and digital IO in a correlated way, but it only works on 6115 and 6120 devices 😞

Can somebody point me in the right direction?


Peter

[JorisV]

Hi Peter,

Your cannot do buffered digital I/O with your daqpad. It doesn't have that capability. You can only make direct software calls with digital read/write from/to your port. So your digital IO is completely software clocked and not hardware clocked. The example you are trying is only for specific Simultanuous sampling boards or now also for M-series boards that are able to do correlated DIO.

Use the Cont Acq&Graph Voltage-Int Clk.vi example for your analog measurements. (NI Example Finder) For your digital IO you can only use the examples like Read Dig Chan.vi, Read Dig Port,...

There are indeed some slow performance issues with single point I/O Operations, that is correct.

Check the explaination below:

DAQPads are offered for the Universal Serial Bus (USB) and the IEEE 1394 (also known as FireWire). Both of these standards use a high-speed serial communication protocol between the computer and the device with a bandwidth up to 12 MB/s for USB and 400 MB/s for FireWire.

During a single point operation, the DAQ device requires a complete set of configuration commands. This is done through serial communication (USB or FireWire), making the process slower than in a PCI-based board. The speed obtained for single point operation in a DAQPad is system dependent; this means that your computer processor, memory, bus speed, and other factors alter the speed at which you can do single-point operations with a DAQPad.

For example, on the DAQPad-6020E, timed non-buffered analog input operations are limited to about 50 Hz. At higher rates, the software may become unresponsive. On a FireWire device, you can expect stable operation around 3,000 Hz. But again, these figures are system dependent.

Regards.

JV
NI

[Peter D'Hoye]

---

@JorisV wrote:
Use the Cont Acq&Graph Voltage-Int Clk.vi example for your analog measurements. (NI Example Finder) For your digital IO you can only use the examples like Read Dig Chan.vi, Read Dig Port,...

---

Hi Joris,

thanks for making this 100% clear...

I can't seem to find the example you mention. FYI, the 6020E isn't supported by DAQmx and most of the NI examples out there, so I'd rather be sure a certain example supports our DAQPad 6020E.

thanks,
Peter

[Peter D'Hoye]

---

@Peter D'Hoye wrote:

I can't seem to find the example you mention.

---

Addendum...: found the example, it uses DAQmx, but DAQmx doesn't support the 6020E 😞

Peter

[JorisV]

yep, you are right. I was a little bit too fast with my answer. Your device is a bit older so you can only use traditional daq. Basically no buffered acquisition is supported by this device.

You can use the following examples that get installed with the traditional daq driver:

Cont Acq&Chart (hw timed).vi/(immediate) those are the only two continuous examples that support the daqpad 6020E. Check under the E-series folder of the traditional daq folder for the Vi's that support your daqpad. The names of the VIs should be similar for older versions of NI-daq.

Regards.

JV

[Peter D'Hoye]

---

@JorisV wrote:
yep, you are right. I was a little bit too fast with my answer. Your device is a bit older so you can only use traditional daq. Basically no buffered acquisition is supported by this device.

You can use the following examples that get installed with the traditional daq driver:

Cont Acq&Chart (hw timed).vi/(immediate) those are the only two continuous examples that support the daqpad 6020E. Check under the E-series folder of the traditional daq folder for the Vi's that support your daqpad. The names of the VIs should be similar for older versions of NI-daq.

Regards.

JV

---

OK, thanks for the info and your time.


Peter D'Hoye