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Discussion in 'Electronic Design' started by Jamie, Apr 11, 2013.

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  1. Jamie

    Jamie Guest

    every use this?
    http://www.pololu.com/catalog/product/391

    I need one that supports the DCD and RI inputs.. it seems to
    have it. It also has a on board 3.3v reg output so I could use
    that to drive the little uC and it has the access pin for the
    5 volts from the port.

    I find that at times it's best to buy ready made modules for
    some common off the wall usage's, since this has to work in
    windows. I'll be writing the host software but I want this to
    be a common interface, incase we decide to spread it on other
    platforms.

    Jamie
     
  2. Guest

    I haven't used this part in particular.

    You may already know the following, but here is some generic USB-to-
    serial advice...

    Under Windows, this will get assigned to about COM5 or above. Depending
    on the provided drivers and possibly what version of Windows you have,
    sometimes the COMx number will bump up by one every time you insert and
    remove the device; during development you might manage to run Windows
    out of COMx port names. This isn't usually a problem for end users,
    because they don't plug and unplug as much as you will, but it might
    catch some of them.

    The chip probably has a fixed USB vendor and device ID, so it will
    always show up as something like "SiLabs CP2102 Serial Converter" to
    Windows. If you want it to show up as a "Jamie Niftytron", you need to
    be able to reprogram these IDs; some chips support this and some don't.
    The whole spiel is to get a USB vendor ID from the USB people, program
    that ID into the chip, and then ship a file to tell Windows that vendor
    0x4321 is "Jamie" and device 0x1234 is "Niftytron". Note that if you
    program your Windows application to assume that the first COMx port that
    identifies as a SiLabs CP2102 is your gadget, then your first customer
    will have six other SiLabs CP2102 USB-to-serial converters plugged in to
    their PC. :)

    One trap to watch out for: the USB-to-serial chip and your
    microcontroller have to agree on the serial parameters (bit rate,
    parity, stop bits, etc.) When people started retrofitting USB-to-serial
    chips onto existing devices, sometimes they forgot this, and their
    software would tell the microcontroller to switch to 9600 8N1 while the
    USB-to-serial chip was still on 2400 7O2. The end-user fix was to power
    cycle, sometimes involving dissasembly to disconnect a battery.
    I agree. You probably don't want to write OS-level drivers (for any OS)
    if you don't have to. It depends on the end use, but right now you'd
    plausibly have to support four different versions of Windows (XP, Vista,
    7, 8), at least a couple of different Linux kernel versions (2.6.x and
    something newer, probably 3.x.x), and at least a couple of different
    versions of OS X (probably 10.7 and 10.8).
    For a while, if you wanted it to run on Linux, the standard advice was
    to use the Prolific PL2303 chip. The driver for this has been in the
    kernel for a while and works well. There may be good drivers for
    other chips now; I haven't looked lately.

    The chip vendor will often say they support Linux, but the binary driver
    they provide will always be for an outdated kernel version that nobody
    runs. If the chip vendor provides source for a driver (uncommon), it
    will also only build against an old kernel, and be hard for end-users to
    install. If the driver ships with the kernel from kernel.org, and is
    present on recent versions of well-known distributions (Fedora, Debian,
    Gentoo, SuSE, etc), then it will probably work OK.

    I don't know what the situation on OS X is like. Probably you have to
    trade a $1 chip for a $5 one that comes in a sleek white case, and pay
    Apple to get your software on iTunes, or something. :)

    Matt Roberds
     
  3. Jasen Betts

    Jasen Betts Guest

  4. Jasen Betts

    Jasen Betts Guest

    Not in this case. the driver is open source and works just fine.
    and ever since I first encountered it several years ago.
     
  5. Guest

    Just use one of these:

    http://www.ftdichip.com/Products/Cables/USBTTLSerial.htm
     
  6. This happens if the USB device does not have a serial number
    programmed. Windows does not know if this is a new device or the same
    one, so it plays it safe and assumes it's a new one.
    Getting rid of these stale com ports is easy. Just make Windows show
    nonpresent devices (http://support.microsoft.com/kb/241257), and then
    delete them form Device Manager.
    I have tried both FTDI's FT232R and SiLabs' CP2102 with a plain
    Ubuntu, installed off the CD. Both worked without any user
    intervention at all.

    One thing to note about the Prolific chip: There are counterfeit chips
    on the market. They will not work with Prolific's official drivers if
    you have Windows 7 or later. There are hacked drivers available, but
    they don't work well. In Linux, the fake chips seem to work fine.
     
  7. Jamie

    Jamie Guest

    Iserial.. Ilink, I can see it now :)

    Jamie
     
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