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Propeller Proto USB powered by USB? — Parallax Forums

Propeller Proto USB powered by USB?

FranklinFranklin Posts: 4,747
edited 2011-06-05 16:28 in Propeller 1
I do not see a way to power the USB proto board from USB. Am I missing something or was that not thought to be a good idea? It would make my prototyping easier.

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2011-06-04 11:11
    That's right. Without modifications, you can't power the USB ProtoBoard from USB. If you look at the FTDI chip's documentation, you'll see that it does have a +5V output derived from the USB power leads. This is only used for powering the FTDI chip itself and, indirectly, the LEDs attached to it. There are other USB to serial interfaces that make the +5V externally available and you could use those as models for modifications. Look at the Parallax C3 Board schematic for one example. The ASC Board is another one that allows power to be supplied from USB. Remember that there's limited current available, 100mA normally, 500mA in high power mode.
  • jazzedjazzed Posts: 11,803
    edited 2011-06-04 11:21
    Why not just hack the board? Disconnect the 5V regulator and add a wire (prefer an inductor) from the USB power pin to the 3.3V regulator input.
  • Mike GreenMike Green Posts: 23,101
    edited 2011-06-04 11:34
    Correction ... The FTDI chip has a 3.3V output. You would have to tie the USB +5V line to the output terminal of the disconnected 5V regulator as jazzed suggested, preferably through a 500mA resettable fuse (you really don't want to take a chance on damaging your PC's USB port if there's a short circuit on your ProtoBoard).
  • FranklinFranklin Posts: 4,747
    edited 2011-06-04 15:29
    Bummer. Why would Parallax handicap the board like that? It would seem so easy to power the chip from USB.
  • LeonLeon Posts: 7,620
    edited 2011-06-04 15:48
    Because they didn't know what people would be doing with it, and were playing safe. I have some other boards with a USB connection that require a separate supply.
  • Mike GreenMike Green Posts: 23,101
    edited 2011-06-04 16:05
    The problem is that you're not really allowed to just tap into USB power. There are rules and violating them has the potential of damaging the USB host. With more and more devices using USB as a source of power, like for charging batteries, there's been an improvement in USB host controllers, so that's not so much of a problem. Still, the maximum current drawn has to be limited. There are limits to the current prior to the USB client being recognized by the host and a limit of 100mA for standard USB clients or 500mA for high power USB clients once the client has been recognized (enumerated) by the host system.
  • RaymanRayman Posts: 14,996
    edited 2011-06-04 17:04
    It's true that there are strict rules, but it's also true that a lot of items bend/break the rules without repute...

    I moded a demo board to be USB powered and I'm sure you can do the same for a proto board.

    I use a powered USB hub in between it and the computer to give some level of protection in case of short-circuit...
  • jazzedjazzed Posts: 11,803
    edited 2011-06-04 17:15
    Rayman wrote: »
    It's true that there are strict rules, but it's also true that a lot of items bend/break the rules without repute...

    I moded a demo board to be USB powered and I'm sure you can do the same for a proto board.

    I use a powered USB hub in between it and the computer to give some level of protection in case of short-circuit...

    I've had a few shorts :)

    Good computers detect a power surge and shut down the port. No so good computers make that funny carbon smell ... but the port where I had that accident still works perfectly. YMMV. Preventive measures should be used.
  • FranklinFranklin Posts: 4,747
    edited 2011-06-04 19:23
    All your posts make sense but it would still help with prototyping if you could load and run code without adding the need for a second cord connected to the board. I have to find my power supply and an outlet for it when I switch to propeller work and have been pulling the boebot off the shelf for power more than once. Just saying.....
  • RaymanRayman Posts: 14,996
    edited 2011-06-04 19:55
    BTW: There are also USB cables that end in the barrel connector compatible with proto and demo boards... That's another way to supply power. Does the same thing as a jumper wire, but without soldering...
  • PJAllenPJAllen Banned Posts: 5,065
    edited 2011-06-04 19:59
    You know how it is, Franklin: People get carried away ("Oh, that's showing the '+' as the center terminal?..."), you have to cater to the LCDs. The next thing you know they'd try to run motors off the USB 5V and then great wailing and gnashing of teeth would follow (anger, vituperation, "...so is my USB stuffed?").

    If you're big enough to take the hit, run the jumper, like the man said, and go with it.
  • FranklinFranklin Posts: 4,747
    edited 2011-06-04 20:53
    OK, but if I go that way I want my cookie..:lol:
  • Peter KG6LSEPeter KG6LSE Posts: 1,383
    edited 2011-06-04 21:10
    PJ is right . sadly I see these all the time
    http://www.thinkgeek.com/computing/usb-gadgets/cf6d/
    http://www.thinkgeek.com/geektoys/japanfan/9c89/

    The latter one My dad brought back from Japan last year . Oy Vey NOT on my computer !

    I did like Rayman here
    I use a Hub that I know has a Good Over curret protection in it .
    you can buy some VERY NICE Isolators for your computer and Its worth the cost !

    http://www.bb-elec.com/product_family.asp?FamilyId=651
    Now you can do just about any thing you want with USB with out fear ( or as much fear)



    EDIT ( Oh dear now what a 8 trac USB . http://www.thinkgeek.com/electronics/digital-conversion/e6df/ sheese )
    http://www.thinkgeek.com/tshirts-apparel/unisex/generic/a651/

    Peter
  • davidsaundersdavidsaunders Posts: 1,559
    edited 2011-06-05 07:27
    Franklin: If you need power with out USB mods, or an external power supply, use a battery pack with rechargeable batteries, I use both 9v batteries and battery packs with 4 D cells on the Proto board and it works well. Just wire the battery pack to a barrel plug that fits the Proto Board. The Packs using D Cells last a lot longer than the 9V batteries.
  • Cluso99Cluso99 Posts: 18,069
    edited 2011-06-05 16:28
    If you know that you will not be using a lot of power, then modify you protoboard with a 3pin link to use either USB or external power. The 3pin prevents both from supplying power. You could also use a switch instead. I agree, I don't like extra cords, and sometimes you forget the adapter when going mobile. But OTOH Parallax do not know what is to be connected to this pcb and they would not want to be blamed for causing damage to a pc or laptop.
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