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Power Problem? — Parallax Forums

Power Problem?

mwkohlermwkohler Posts: 7
edited 2007-09-17 15:51 in General Discussion
I have two sx48 proto boards·both running at 50,000 hz and i am trying to serially send data from one to the other.· I can only get them to communicate when I leave the sx-key on the board (after programing it) that is sending the data.· The boards work great like this.· Otherwise, when I disconnect the sx-key, there is no sign of communication.· I have tried several different Baud rates all the way down to 1200 with no avail.· I have included the programs I am using in case it is something I am doing with the software.· I figure it is a power problem since when the key is connected to the board it probably is boosting the power through the usb port.· I just don't know where to go from here.· Any help is appreciated.

Comments

  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2007-09-16 18:46
    Could it be that you have forgotten to put in a resonator?
    Generally, you remove it to program and the SXKey provides the clock.
    So it must be replaced.

    Alternately, both resonators or just one is hanging up due to the wrong fuse setting. Try to find the setting that requies the least amount of power to properly drive your resonator or crystal.

    It certainly would help to verify one at a time by connecting to a reliable serial port.

    Are you really clocking at 50Khz? [noparse][[/noparse]Your software says 50Mhz]
    At 50Khz, it seems that you are too slow for a resonator. If you are relying on the internal RC circuit or an external RC circuit, it is not stable enough for serial communications. As the temperature rises, it will drift up to 7% and serial needs no more than 3% drift at best.

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  • BeanBean Posts: 8,129
    edited 2007-09-16 19:20
    Try OSCHS2 on the device line.

    Bean

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  • mwkohlermwkohler Posts: 7
    edited 2007-09-17 00:22
    Bean - that did it!· Changing oschs1 to oschs2 fixed the problem.· Any insight as to why?· Is it something to do with how much power is directed the resonator?· Thanks a lot for your help.

    Post Edited (mwkohler) : 9/17/2007 1:07:45 AM GMT
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2007-09-17 15:51
    Bean know more in detail and from experience.

    But for what I can gather, the published resonator settings in relation to frequency and products are merely guidelines. At times they don't reflect reality and some of the older SX publications make conflicting suggestions about which level is appropriate.

    In concept, the settings themselves actually provide stepped increases in driving power for the resonators.

    So it is a matter of finding the minimum driving power that provides a stable clock. I suppose that you could drive at an excessively high level and waste power, but why do so.

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    "Everything in the world is purchased by labour; and our passions are the only causes of labor." -- David·Hume (1711-76)········
    ···················· Tropically,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan
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