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sx28 proto board stand alone — Parallax Forums

sx28 proto board stand alone

LTAYLO91LTAYLO91 Posts: 8
edited 2008-01-20 05:05 in General Discussion
My sx28 proto board will not run my program without the sx-key attached.
My sx tech board w/sx28 will run just fine on its own. Does the proto board
need a clock sig to run?

The DEVICE and FREQ settings I'm using are

DEVICE SX28, OSC4MHZ, TURBO, STACKX, OPTIONX
FREQ 4_000_000

Thanks guys!
Any help would be greatly appreciated.

Comments

  • PJAllenPJAllen Banned Posts: 5,065
    edited 2008-01-19 17:15
    Yes -- either an oscillator, a crystal, or a resonator.

    Post Edit -- You can also opt to use the internal oscillator if you aren't doing time-critical operations.

    Post Edited (PJ Allen) : 1/19/2008 5:23:25 PM GMT
  • LTAYLO91LTAYLO91 Posts: 8
    edited 2008-01-19 17:36
    I have tried to use a 4Mhz resonator with no luck. In the proto board
    document it says on page 1 ," clock config supported are TTL oscillator
    (dip-8 - clock label), resonator (sip3 - X1 header), crystal (hc/49 - X2 header)".
    I put the resonator in the X1 header and also tried the X2 header with no luck
    on eather. Also, are you saying that the surface-mount sx28 will not run with
    the internal clock but the dip sx28 will?
  • LTAYLO91LTAYLO91 Posts: 8
    edited 2008-01-19 17:44
    Do I need to do any thing different with the proto board
    to use the internal oscillator? Using the internal osc. on
    the sx/tech board works fine.
  • ZootZoot Posts: 2,227
    edited 2008-01-19 17:46
    It should run w/o key and w/o external crystal/resonator if that's how it's configured.

    One thought -- you have OSC4MHZ specified in your device line -- this will run the chip from the internal RC oscillator. If you want to use an external 4mhz clock source, you would want to specify OSCXT1 or OSCXT2.

    Also, when you want to run standalone (w/o key) did you RUN -> PROGRAM?

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  • LTAYLO91LTAYLO91 Posts: 8
    edited 2008-01-19 19:11
    Well, I pulled out a second sx28proto board and downloaded a
    program to make rb.5 high for 500 mS and then low for 500 mS
    with no circuits connected. This works fine with the sx-key removed.
    Must be something with my circuit?? Leds connected w/ 470 ohm
    resisters to pins rb.5,rb6,rb7, and an ir detector on ra.1. One thing
    that is defenetly a problem is, if the sx-key is not pluged into the
    board, the green power led on the board is very dim. When the sx-key
    is pluged in the board works fine , but, the sx-key and voltage reg. on the
    board get pretty hot.
  • ZootZoot Posts: 2,227
    edited 2008-01-19 19:37
    if the sx-key is not pluged into the
    board, the green power led on the board is very dim.

    - this seems unusual

    When the sx-key
    is pluged in the board works fine , but, the sx-key and voltage reg. on the
    board get pretty hot.

    - the Key itself is powered by the board it is plugged into -- so you could expect the regulator to be drawing more current -- but pretty hot seems weird -- what are you using to power the board? I fried the regulator on one proto-board when I used a wall-wart with the board that output way more voltage than it was labeled for (I didn't check it with a meter beforehand -- now I know better).

    - do you have a 220ohm or so resistor between the output pin of the IR detector and the input pin on the SX? You don't want the detector to sink/source too much current through the pin. This will also protect the pin in case you accidentally make it an output and the detector is in the opposite state (short circuit)

    - do you get 5v out of the regulator on that board with nothing else hooked up?

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    When the going gets weird, the weird turn pro. -- HST

    1uffakind.com/robots/povBitMapBuilder.php
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  • LTAYLO91LTAYLO91 Posts: 8
    edited 2008-01-20 04:27
    Good call Zoot. My wall wort is rated for 9v 300ma. Its putting
    out 17v!! WTF. Is this the way they normaly fail? The reg is putting
    out 5v but it is hot. I got the circuit from the sx/b examples in the help menu.
    Im going to rebuild the circuit on another proto board tomorrow
    and use a 9v batt to power it and see how that changes things.

    Post Edited (LTAYLO91) : 1/20/2008 4:34:00 AM GMT
  • ZootZoot Posts: 2,227
    edited 2008-01-20 05:05
    Somebody said...
    My wall wort is rated for 9v 300ma. Its putting
    out 17v!!

    If you do a search around the forums, you'll see there is a *lot* of commentary about this. The short version is that common wall-warts will deliver something like their rated voltage UNDER LOAD. So if you are only drawing 100ma, you're going to get way more voltage. Also they are not regulated, generally, and their actual voltage can vary.

    The finger test is good too -- if it's too hot to press your finger on it and keep it there, it's too hot.

    In my one frying experience, the chip started acting funny and the reg. was very hot. I checked voltage out of the reg. and it was around 5.7 (the SX is rated to 5.5). I didn't fry the SX, but the LDO regulator wouldn't give any kind of stable voltage after that, even when given 6-7 volts in.

    In any case, if you are powering regulators from wall-warts you might want to think about using non-LDO regulators -- they can dissipate more heat, and they expect voltage at least 2-3 volts higher than their rated output (as opposed to LDOs which are good at Vins much closer to their rated output. The LDOs are good for battery power where the battery Vin voltage might only be .5 or 1 volt above the 5v out from the reg.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    When the going gets weird, the weird turn pro. -- HST

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