VISA USB

[Cluo]

While NI-VISA supports three types of USB pipes: control, bulk, and interrupt, Does it means we can develop any USB device driver upon this three types and need not any other low level layer knowledge? For example, if we write some raw data, we just use the bulk mode to write, and then the usb data out would output our written data.

[Intaris]

USB is only a communications protocol.  What happens with the data fter it is transmitted depends entirely ont he hardware attatched.

VISA supports Bulk, Control and Interrupt transfers.  Everything which can be done with these three modes of USB communication can beimplemented with VISA.  No further low-level knowledge is needed, but it's recommended to know a bit about the USB specification.

Refer to my two nuggets listed in my signature.

Regards

Shane

[Cluo]

Thanks for your relay.

I want to confirm that if all the USB devices conform to the three transfer modes(actual four modes).  The transfer mode is defined in the USB protocol? Every USB devices should just conform to the four transfer modes?

[Intaris · Accepted solution]

I don't understand your question.

VISA supports three of maximum 4 allowable different transfer mechanism available for USB.  Isochronous is not supported and is a lossy transfer which is not interesting for test and measurement anyway.  It is meant only for audio and video where a few lost packets are not so bad.

ALL USB devices can support ONLY these four types of transfer.  Note that this not describe WHAT should be transferred using these methods, only HOW the data is transferred.

Each device implements its own mix of commands which can be received either by control transfer (all devices support a certain set of commands on control endpoint zero for configuring the device), Bulk or Interrupt or a mixture of all three.

If a device does something different than is outlined in the USB protocol specification document then it is not USB conform.

Shane.

[cocopa]

Hi Intaris!

I'm using the example that comes with labview 8.5 , VISA USB RAW-Control.vi, to send  requests to my usb device but it doesn't seem to work.I have specified some vendor requests in my code for the usb controller (CyUSB by Cypress) and worked ok with cypress interface.When i try to send these requests through labview,i fill in the fields request type,value etc. ,according to the programmer's reference for CyUSB and although it seems like the request is sent,i don't get the response i'm expecting from my usb device.What could be the problem?Can anyone help?

[Boone301]

Hi all,

I'm study too:

http://forums.ni.com/t5/LabVIEW/How-to-communication-with-chip-after-install-driver-by-Driver/td-p/2...

My SkyPE: boone301,

Br

Boone