Image Formats - Basics

By admin | May 20, 2007

    There are a lot of image formats and hundreds of software programmes capable of converting image formats from one to another. Sometimes individual graphic (image) format is native for some graphic application and may be as an export option in another graphic application (or may be not). In that case may arise a need to convert specific image into native format of that graphic application. Here is a list of some graphic applications and their native image formats:

    Besides, there are a number of image formats that are considered as standard. A standard image format is one that is cross-platform compatible and supported by the majority of graphics applications.

    The most common standard bitmap-based image formats are TIFF (Tagged Image File Format), JPG (Joint Photographic [Experts] Group), GIF (Graphics Interchange Format), and PNG (Portable Network Graphics). On the Windows platform BMP (Bit Mapped Pictures) is a standard format and PICT is a standard bitmap format on the Macintosh. Photoshop’s PSD format is supported to some degree by most graphics applications, but you should take into account that transferring PSD between non-Adobe applications may give unexpected results.

    The most common standard vector-based formats are EPS (Encapsulated PostScript) and AI. On the Windows platform, most vector-based software also supports WMF (Windows Metafile Format) and EMF (Microsoft Enhanced Metafile Format) formats.

    While sending files over the Internet or transporting them between graphics applications, it is recommended to use one of these standard formats, or the results may be unexpected. When sending graphic images via email and the Web, it is best to use JPEG or GIF format, which can be displayed by any Web browser on any computer. If in doubt, ask the recipient of your files which image formats they can accept.

Sources: http://graphicssoft.about.com/od/aboutgraphics/a/convertgraphics.htm, http://graphicssoft.about.com/od/glossary/g/nativeformat.htm, http://graphicssoft.about.com/library/glossary/bldefstandardformat.htm

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Flash Drives Versus Other Storage Devices

By admin | May 20, 2007

Source: http://www.usbflashdrive.org/usbfd_vs.html#

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Flash Drives - Components

By admin | May 20, 2007

The device is fitted on one end with a single male type-A USB connector. Inside the plastic casing is a small printed circuit board. Mounted on this board is some simple power circuitry and a small number of surface-mounted integrated circuits (ICs). Typically, one of these ICs provides an interface to the USB port, another drives the onboard memory, and the other is the flash memory.

Essential components:

There are typically three parts to a flash drive:

Additional components:

The typical device may also include:

Internals Of A Typical Flash Drive
Internals Of A Typical Flash Drive

1 USB connector
2 USB mass storage controller device
3 Test points
4 Flash Memory chip
5 Crystal oscillator
6 LED
7 Write-Protect Switch
8 Space for second flash memory chip

Source: http://en.wikipedia.org/wiki/Flash%5Fdrive

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Flash Drives - Overview And Characteristics

By admin | May 19, 2007

    A small, portable NAND-type flash memory card that plugs into a computer’s USB port and functions as a portable hard drive. USB flash drives are compact and easy-to-use devices that are similar in use to your computer hard drive. Memory capacity typically ranges from 8 megabytes up to 64 gigabytes, limited only by current flash memory densities, although cost per megabyte increases rapidly at higher capacities due to the expensive components. USB flash drives are touted as being easy-to-use as they are small enough to be carried in a pocket or conveniently around your neck or on a keychain, and can plug into any computer with a USB drive. They are really ultimate portable storage. USB flash drives have less storage capacity than an external hard drive, but they are smaller and more durable because they do not contain any internal moving parts. USB flash drives finally fulfill the real promise of the digital age: complete freedom and mobility.
    Despite the different brands and names you’ve heard for USB flash drives – JumpDrives™, Pocket drives™, Pen drives™, and Thumb drives™ – they all pretty much operate the same way. The difference is mostly in price, capacity, design, functions and features (for example, some have built-in MP3 players).
    USB flash drives have several advantages over other portable storage devices, particularly the floppy disk. They are generally faster, hold more data, and are considered more reliable (due to their lack of moving parts) than floppy disks. These types of drives use the USB mass storage standard, supported natively by modern operating systems such as Linux, Mac OS X, and Windows XP.
    A flash drive consists of a small printed circuit board encased in a robust plastic or metal casing, making the drive sturdy enough to be carried about in a pocket, as a keyfob, or on a lanyard. Only the USB connector protrudes from this protection, and is usually covered by a removable cap. Most flash drives use a standard type - A USB connection allowing them to be connected directly to a port on a personal computer.
    Most flash drives are active only when powered by a USB computer connection, and require no other external power source or battery power source; they are powered using the limited supply afforded by the USB connection. To access the data stored in a flash drive, the flash drive must be connected to a computer, either by direct connection to the computer’s USB port or via a USB hub.

Sources: http://www.webopedia.com/TERM/U/USB_flash_drive.html, http://www.usbflashdrive.org/usbfd_overview.html, http://www.usbflashdrive.org/usbfd_overview.html, http://en.wikipedia.org/wiki/Flash%5Fdrive

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USB - Version History

By admin | May 19, 2007

USB Version History

USB logoOriginal USB logo

USB On-The-Go Supplement

Wireless USB

Source: http://en.wikipedia.org/wiki/Usb

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USB and FireWire

By admin | May 18, 2007

FireWire

USB was originally seen as a complement to FireWire (IEEE 1394), which was designed as a high-speed serial bus which could efficiently interconnect peripherals such as hard disks, audio interfaces, and video equipment. USB originally operated at a far lower data rate and used much simpler hardware, and was suitable for small peripherals such as keyboards and mice.

However, Intel was not interested in paying the near-dollar license fee to add an IEEE 1394 subsystem to their board. The fee was reduced to a flat 25 cents, but Intel prefered to push for its own USB 2.0 standard. As a result, they were rarely provided as standard equipment on computers other than Apple Macintosh computers (Apple owns rights to the FireWire standard), and peripheral manufacturers offered many more USB devices. Moreover, USB 2.0 Hi-Speed reached a performance level sufficient for consumer equipment while retaining compatibility with older devices. An example of how the popularity of USB displaced FireWire in a commercial device is the Apple iPod. It was originally released with a FireWire connector, which was eventually modified to allow for both USB and FireWire connections when the product was released for Windows. The iPod now relies solely on USB for data and only allows a FireWire connection to charge the battery.

Today, USB Hi-Speed is rapidly replacing FireWire in consumer products. FireWire retains its popularity in many professional settings, where it is used for audio and video transfer, and data storage.

Technical differences
The most significant technical differences between FireWire and USB include the following:

These and other differences reflect the differing design goals of the two buses: USB was designed for simplicity and low cost, while FireWire was designed for high performance, particularly in time-sensitive applications such as audio and video.

USB 2.0 Hi-Speed vs FireWire

The signaling rate of USB 2.0 Hi-Speed mode is 480 megabits per second, while the signaling rate of FireWire 400 (IEEE 1394a) is 393.216 Mbit/s [6]. USB requires more host processing power than FireWire due to the need for the host to provide the arbitration and scheduling of transactions. USB transfer rates are theoretically higher than FireWire due to the need for FireWire devices to arbitrate for bus access. A single FireWire device may achieve a transfer rate for FireWire 400 as high as 41 MB/s, while for USB 2.0 the rate can theoretically be 55 MB/s (for a single device). In a multi-device environment FireWire rapidly loses ground to USB: FireWire’s mixed speed networks and long connection chains dramatically affect its performance.

The peer-to-peer nature of FireWire requires devices to arbitrate, which means a FireWire bus must wait until a given signal has propagated to all devices on the bus. The more devices on the bus, the lower is its peak performance. Conversely, for USB the maximum timing model is fixed and is limited only by the host-device branch (not the entire network). Furthermore, the host-centric nature of USB allows the host to allocate more bandwidth to high priority devices instead of forcing them to compete for bandwidth as in Firewire.

Despite all this and despite USB’s theoretically higher speed, in real life benchmarks the actual speed of FireWire hard drives nearly always beats USB 2 hard drives by a significant margin (for example[7]). In addition to this some operating systems take a conservative approach to scheduling transactions and limit the number of transfers per frame, reducing the maximum transfers from, say, the theoretical 13 per frame to 10 or 9.

However, on Bare Feats, the Mac only USB 2.0 vs. FireWire speed comparison, the poster notes the measured PC speed of USB 2.0 instead of Mac “The Windows PC implementation of USB 2.0 puts the Mac to shame. Today we tested the same USB 2.0 drive/enclosure on a Windows PC (3GHz Pentium 4) with built-in USB 2.0 on the motherboard, similar to Apple’s approach. We measured 33MB/s READ and 27MB/s WRITE.”

In 2003, FireWire was updated with the IEEE 1394b specification. This provides a new mode called S800, which operates at 786.432 Mbit/s. S800 requires a new physical layer, but S800 nodes can be connected to existing FireWire 1394a ports, just as USB Hi-Speed nodes will operate with older full-speed hosts. However, unlike USB Hi-Speed systems, which can change the speeds on each branch, a 1394a device on a 1394b system requires all devices to fall to 1394a speeds. IEEE 1394b also provides rates up to approximately 3.2 Gbit/s; however, the higher rates use special physical layers which are incompatible with 1394a devices.

Source: http://en.wikipedia.org/wiki/Usb

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Off-Road Navigation with GPS Fugawi Global Navigator 3.3.1(9)

By admin | May 18, 2007

Off-Road Navigation with GPS Fugawi Global Navigator 3.3.1

(ending)

Documentation
Help is available within the PPC application but is limited to short descriptions of the main features available.

fugawi-help.gifFigure 19: Help function within Global Navigator. A little light, but it covers the basics to get you going.

Better documentation is available in the PC application but there is definitely an assumption that you understand the basics of mapping such as scale, waypoints and layers.

Conclusions
For those looking to trek off the roadways, the PDA version of Global Navigator provides the basic functionality needed to navigate terrain. While other programs, such as GPSTuner can work with generally available maps such as Google Earth, Global Navigator is one of the few products which provides topographic and marine products for Canada. With the addition of some trip computer functionality to the PDA version and more modern topographic and street overlays, this could become the ultimate off-road companion.

Source: pocketpcthoughts.com

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USB - Device Classes

By admin | May 16, 2007

Devices that attach to the bus can be full-custom devices requiring a full-custom device driver to be used, or may belong to a device class. These classes define an expected behavior in terms of device and interface descriptors so that the same device driver may be used for any device that claims to be a member of a certain class. An operating system is supposed to implement all device classes so as to provide generic drivers for any USB device.

Device classes are decided upon by the Device Working Group of the USB Implementers Forum. If the class is to be set for the entire device, the number is assigned to the bDeviceClass field of the device descriptor, and if it is to be set for a single interface on a device, it is assigned to the bInterfaceClass field of the interface descriptor. Both of these are a single byte each, so a maximum of 254 different device classes are possible (values 0×00 and 0xFF are reserved). If bDeviceClass is set to 0×00, the operating system will look at bInterfaceClass of each interface to determine the device class. Each class also optionally supports a SubClass and Protocol subdefinition. These can be used as the main device classes are continuously revised.

The most used device classes (grouped by assigned class ID) are:

Source: http://en.wikipedia.org/wiki/Usb

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USB - Power Supply

By admin | May 16, 2007

Standard

The USB specification provides a 5 V (volts) supply on a single wire from which connected USB devices may draw power. The specification provides for no more than 5.25 V and no less than 4.35 V between the +ve and -ve bus power lines.
Initially a device is only allowed to draw 100 mA. It may request more current from the upstream device in units of 100 mA up to a maximum of 500 mA. In practice, most ports will deliver the full 500 mA or more before shutting down power, even if the device hasn’t requested it or even identified itself, but any device that behaves in this way is, by definition, not a USB device. If a (compliant) device requires more power than is available, then it cannot operate until the user changes the network (either by rearranging USB connections or by adding external power) to supply the power required.
If a bus-powered hub is used, the devices downstream may only use a total of four units — 400 mA — of current. This limits compliant bus-powered hubs to 4 ports, among other things. Equipment requiring more than 500 mA, hubs with more than 4 ports and hubs with downstream devices using more than four 100 mA units total must provide their own power. The host operating system typically keeps track of the power requirements of the USB network and may warn the computer’s operator when a given segment requires more power than is available.

Non-standard

A number of devices use this power supply without participating in a proper USB network. The typical example is a USB-powered reading light; fans, battery chargers (particularly for mobile telephones) and even miniature vacuum cleaners are also available. In most cases, these items contain no electronic circuitry, and thus are not proper USB devices at all. This can cause problems with some computers—the USB specification requires that devices connect in a low-power mode (100 mA maximum) and state how much current they need, before switching, with the host’s permission, into high-power mode.
Some USB devices draw more power than is permitted by the specification for a single port. This is a common requirement of external hard and optical disc drives and other devices with motors or lamps. Such devices can be used with an external power supply of adequate rating; some external hubs may, in practice, supply sufficient power. For portable devices where external power is not available, but not more than 1 A is required at 5 V, devices may have connectors to allow the use of two USB cables, doubling available power but reducing the number of USB ports available to other devices. Amongst others, a number of peripherals for IBM laptops (now made by Lenovo) are designed to use dual USB connections.
USB-powered devices attempting to draw large currents without requesting the power will not work with certain USB controllers, and will either disrupt other devices on the bus or fail to work themselves (or both).

Source: http://en.wikipedia.org/wiki/Usb

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Off-Road Navigation with GPS Fugawi Global Navigator 3.3.1(8)

By admin | May 15, 2007

Off-Road Navigation with GPS Fugawi Global Navigator 3.3.1

(continuation)

fugawi-newrouteb.gifFigure 15: Creating the route by adding existing waypoints.

Global Navigator then creates a route by connecting the waypoints.

fugawi-rtepic.gifFigure 16: A route created from 6 waypoints.

To navigate the route, you select it from the menu and then select ‘Navigate’.

fugawi-rteinfo.gifFigure 17: Selecting a route for navigation

Fugawi starts you from the closest waypoint along the route, then points to the next waypoint, along with the compass direction and distance.

fugawi-rtetrack.gifFigure 18: Which way to the next waypoint? (In the example shown, the car wasn’t actually on the route, so ETA and heading for the next waypoint aren’t shown).

If it has current speed info from previous movement, it will also show approximate ETA at the next waypoint. Order of the waypoints (and hence direction of travel) is defined by the order in which they are added, but they can be re-ordered with the route.

…to be continued…

Source: pocketpcthoughts.com

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