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non-destructive "expansion" of Propeller Servo Controller USB — Parallax Forums

non-destructive "expansion" of Propeller Servo Controller USB

TinkersALotTinkersALot Posts: 535
edited 2013-01-20 18:42 in Propeller 1
Let's say, just for the sake of discussion, that I have one of these to start with:

http://www.parallax.com/Store/Microcontrollers/PropellerDevelopmentBoards/tabid/514/CategoryID/73/List/0/catpageindex/2/Level/a/ProductID/595/Default.aspx?SortField=ProductName%2cProductName

and I wanted to make use of P16-P23 (which I see on the schematic are not used for anything) so that I could get 8 more I/O lines to use. How would I go about doing this in a way that reduce the odds I would end up with a $40.00 brick?

Thanks

PS I will be loading different firmware into the little beastie as well to take advantage of these "extra pins"

Comments

  • JonnyMacJonnyMac Posts: 9,108
    edited 2013-01-19 11:22
    It doesn't look like those pins are brought out in a way that you can get to them.
  • kwinnkwinn Posts: 8,697
    edited 2013-01-19 11:46
    As JonnyMac says, It doesn't look like those pins are brought out in a way you can get at them. Hard to say for sure without the board layout. You might (with stress on the might) be able to solder a strip of 8 conductor ribbon cable directly to the pins but I would not recommend it or try it myself. Even if you manage to solder the cable on to the pins it would be a pretty fragile assembly.
  • TinkersALotTinkersALot Posts: 535
    edited 2013-01-19 12:45
    well, geez, I wonder why the opted to waste those pins like that...seems so uncharacteristic; and it would have been so easy to just pull them out to a pin header or something...oh well, 16 I/Os it is then. Thanks for the replies.
  • kwinnkwinn Posts: 8,697
    edited 2013-01-19 23:08
    It does seem like a bit of an oversight to leave all those I/O's inaccessible. It might have made the boards useful to a wider audience even if they were only brought out to a row of pads. Oh well, maybe next rev.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2013-01-20 13:45
    TinkersALot wrote: »
    I wonder why the opted to waste those pins like that...seems so uncharacteristic; and it would have been so easy to just pull them out to a pin header or something...

    I concur.

    The Parallax Range Finder has eight unused pins; while these pins aren't brought out to header pins, they are brought out to solder pads. The Propeller Servo Controller would have been much more appealing with access to the other I/O pins.
  • frank freedmanfrank freedman Posts: 1,983
    edited 2013-01-20 18:42
    Perhaps it was less of an oversight and more of meeting a specific size; smallest possible. Looks like it would have taken significant larger board size to both run the 8 traces as well as provide either pads or header.

    That said, there is nothing that says you can not make a harness up and add your own connections. From looking at the large image on the store page, the pins themselves are accessible with a bit of pad extending beyond the chip. Little #30 kynar wrap wire will solder nicely. If like me geezerhood is starting to set in on the eyes, you can always break out the 2.5x surgical loupes used by who else, surgeons or dentists....... Got mine, US Surgical Instruments 2.5x flip up (far better than the embedded ones my dentist uses, his opinion) for $50.00 on ebay from a dental student.

    Frank
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