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Something like FT245BM for USB 2.0 ? Parallel -> USB with real USB 2.0 bandwidth ?

Discussion in 'Embedded' started by Martin Maurer, Mar 4, 2004.

  1. Hello,

    is there a chip, in functionality like a FT245BM for USB 2.0 ?
    I found on websites mentioning the FT245BM compatible for USB 2.0,
    but i think they don't use USB 2.0, because transfer rate is "only" 1
    MByte/s, which looks like high speed USB.

    Is there a faster parallel USB chip, which achieves more than 1 MByte / s ?
    I think with USB 2.0 there must be at least a factor of 10 to this speed ?


    Martin Maurer, Mar 4, 2004
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  2. Martin Maurer

    Al Clark Guest

    The FT245BM is a USB 2.0 device that can operate at 12 Mb/s (USB full

    Cypress has a high speed part that is functionally similar called the
    SX2. Evidently, they have some drivers that are similar to the DLL that
    FTDI distributes. I am looking into this part for a project, but I don't
    know very many details yet.

    Al Clark
    Danville Signal Processing, Inc.
    Al Clark, Mar 4, 2004
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  3. Martin Maurer

    Max Guest

    I think it's referred to as "full speed" - the fastest USB1.1 could
    Cypress and NetChip have working devices apparently, but I haven't
    used them.
    USB 2.0 goes to 450Mbps, or around 50+MB/sec.

    Be aware that support for high-speed USB 2.0 is somewhat patchy in
    current OSs. Microsoft have released EHCI drivers for XP, and I
    understand that drivers for Linux also exist, but that's about it so
    far as I know.

    Some links and further info here:
    Max, Mar 4, 2004
  4. Martin Maurer

    Glen Atkins Guest

    Stay away from Cypress - we've had nothing but hassles with both the devices
    and the company. NetChip has been great to work with though.
    Wrong, USB 2.0 High Speed is 480 Mbps.

    For whatever reason, USB.org has dropped reference to USB 1.1 for the slower
    devices. All are included in the USB2.0 specification. So, the end user
    and developer has to read deeper than just the spec number in the reference.
    USB High Speed is 480- MBps, Full Speed is 12 MBps, low speed is 1.5 Mbps.
    We have high speed USB devices working in VxWorks as well as Win-XP, and
    Win-2K. There are drivers available for Linux for the NetChip devices as
    Glen Atkins, Mar 4, 2004
  5. The FT245BM is a USB 2.0 device that can operate at 12 Mb/s (USB full
    12 MBit/s was already possible with USB 1.1, for this i don't need USB 2.0
    USB 2.0 supports 480 MBit/s, which should give much more than 1 MByte/s...
    I will have a look on this !


    Martin Maurer, Mar 4, 2004
  6. Martin Maurer

    rickman Guest

    Perhaps someone who designs USB devices can explain this. I have been
    told by the chip companies that USB 2.0 full speed devices are not the
    same as USB 1.1 full speed. I have been told that there are operational
    differences, or enhancements I guess is a better term, that a USB 1.1
    full speed device is not automatically a USB 2.0 full speed device. Is
    that correct? Does USB 2.0 require new features or modes?


    Rick "rickman" Collins

    Ignore the reply address. To email me use the above address with the XY

    Arius - A Signal Processing Solutions Company
    Specializing in DSP and FPGA design URL http://www.arius.com
    4 King Ave 301-682-7772 Voice
    Frederick, MD 21701-3110 301-682-7666 FAX
    rickman, Mar 4, 2004
  7. Perhaps someone who designs USB devices can explain this. I have been
    Could it have something to do with the following:

    1) USB 1.1 with full speed occupies the line (around 100 %) with 12 MBit /
    2) When a USB 2.0 device is used with 12 MBit / s (which is also full
    speed), than only around 12 / 480 is used.

    Only speculation...


    Martin Maurer, Mar 4, 2004
  8. Cypress and NetChip have working devices apparently, but I haven't
    I'm just looking for an USB 2.0 high speed peripheral right now, and of
    course the SX2 was high on the list.
    I saw Netchip devices, but thought that Cypress "visibility" would have make
    the FX2/SX2 family reliable for being widely used.

    Our distributor looks good for Cypress... but what about the devices ?

    Please, could you share with us your bad experiences ?
    Antonio Pasini, Mar 4, 2004
  9. Martin Maurer

    Glen Atkins Guest

    Cypress has proven to be significantly less than reliable as a supplier.
    They have not been responsive to repeated phone calls and emails for support
    that was agreed to while in the hardware design phase.

    The SX2 & FX2 do NOT satisfy USB compliance tests for back drive voltage
    without the addition of obscure hardware & a specific software mechanism.

    NetChip, on the other hand, actually acted like they wanted our business and
    valued us as a customer. They were extremely responsive to ALL issues as
    they came up. Their devices satisfy ALL USB compliance testing without
    extra design caveats.
    Glen Atkins, Mar 4, 2004
  10. Martin Maurer

    Andy Peters Guest

    In the past, Cypress have had no problem lying to your face: "Yes, we
    have no intention of obsoleting these parts."

    That is, until you go into production and actually order the parts,
    and your distributor says they're going away.

    Cygnal's 8051-based USB microcontrollers are USB 2.0 full-speed
    compliant (which means that they only run at 12 Mbps), their
    development kits are pretty cheap, and the chips have in-system debug
    capability (gotta love that). I'm going to use one on my next USB

    Andy Peters, Mar 5, 2004
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