labview能控制usb接口呀？

同问!
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I got a LabVIEW program for digital camera connected to the PC thru USB. Unfor
tunately it is done by ActiveX. So we cannot see how it works. But at least we
know that LabVIEW does support USB DAQ.
However, during the NIweek in the last week, I asked an AE of NI, he did not k
now how to call USB directly in LV, either.
This article may be useful:
http://zone.ni.com/devzone/devzoneweb.nsf/Opendoc?openagent&5A327F009625594786
256A9D0078BA05
USB delivers an inexpensive yet easy to use and operate connection between dat
a acquisition devices/instruments and PCs. USB provides a step up from convent
ional serial port technology by featuring faster performance, hot-pluggable fu
nctionality, built-in operating system configuration, and multi-drop cabling s
o you can connect multiple devices from the same port.
The USB bus embodies several characteristics that make it easier to use than s
ome of the traditional internal PC buses such as PCI and ISA. Devices that con
nect using USB are hot-pluggable, so they eliminate the need to shut down the
PC to add or remove a device. The bus also has automatic device detection, mea
ning that the user does not have to manually configure his device once he plug
s it in. The operating system software should detect and install the device on
its own.
High-speed data and control applications benefit from the ability of USB to de
liver data through either isochronous or asynchronous data transfers. With iso
chronous transfers, the bus guarantees bandwidth with time-based delivery of d
ata packets. Isochronous transport guarantees that a transmission is completed
within a given amount of time, but it does not guarantee that the transmissio
n is received error-free. The USB protocol guarantees devices that have reques
ted isochronous bandwidth a predetermined number of data packets in each frame
. Data-intensive applications often demand this type of guaranteed bandwidth.
On the other hand, measurement and control systems commonly require the abilit
y to respond to events. USB allows any device to generate an asynchronous even
t. Asynchronous transport guarantees accurate delivery, and devices with urgen
t messages can be given priority over all other devices. Applications for asyn
chronous transport include delivering control messages and changing device par
ameters.

USB 2.0
USB 2.0 devices will have a throughput of 480 Mb/s - 40 times faster than the
current standard, thanks to the new specification. National Instruments will c
losely follow the development of the USB 2.0 standard, which is now finalized.
The primary differences between USB 1.1 and 2.0 that impact test and measurem
ent devices are the addition of lower-latency 480 Mb/s transfers and improved
host software specifications. Because all USB 1.1 devices are compatible with
the USB 2.0 standard, current USB devices will not be obsolete. All of Nationa
l Instruments current and future USB products will be USB 2.0 compatible.
National Instruments offers several different types of USB-based devices inclu
ding a 15 MHz digital oscilloscope (NI 5102 for USB), data loggers (NI 4350 fo
r USB), multifunction data acquisition devices (DAQPad-6020E), and digital I/O
devices (DAQPad-6507/8). National Instruments also offers converters for inst
rument connectivity via serial or GPIB. The USB-232 and USB-485 devices offer
up to 4 serial ports per USB connection. The GPIB to USB converter, the GPIB-U
SB-B, allows you to control up to 14 programmable GPIB instruments via a USB p
ort in your computer. You do not need to modify your existing GPIB code to use
the GPIB-USB-B. This controller uses the industry standard NI-488.2 applicati
on programming interface, making the conversion from USB to GPIB transparent t
o the user.
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