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Prop not starting — Parallax Forums

Prop not starting

train nuttrain nut Posts: 70
edited 2010-09-12 21:05 in Propeller 1
I have been using a propeller for about six months now and have been running a 5MHz crystal with the following constants

_clkmode = xtal1 + pll16x
_xinfreq = 5_000_000

just this week it has refused to start with this setup. If I change the clkmode line to

_clkmode = xtal1 + pll8x

it will start as it should

Any ideas why all of a sudden it won't start with pll16x. It will occasionally start if I go back and walk it up from rcfast to pll16x. But that is getting more infrequent. It will work on pll8x but that is too slow for my programming needs. I am not currently at home but I have another prop at home that I can swap out. I also have another 5MHz crystal to try also.

If anyone has any ideas or has seen this phenomenon before please let me know.

Thanks

Ben Stow

Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-09-12 20:22
    What kind of board is the Prop running on?

    -Phil
  • ElectricAyeElectricAye Posts: 4,561
    edited 2010-09-12 20:27
    Any chance this might have something to do with what Mike Green says in the following?:
    http://forums.parallax.com/showthread.php?t=95058&highlight=pllx&page=2

    Would better bypass caps help, perhaps???
  • train nuttrain nut Posts: 70
    edited 2010-09-12 20:43
    The prop and memory are socketed on a Vector prototyping board with the recommended bypass caps. I am using a 7808 reg suppling an LM317 adjustable reg set to 3.3 volts. The 7808 is supplied by a 12volt gel cell. There are other voltages on and around the prop board but these are switched by the the prop through transistor controlled relays (yes the relays have bucking diodes in them). As I said I have been running this setup for about 6 months and this is the first trouble with the pll circuit I have experienced. Thanks for the fast responses. I'll check into it more when I get home where I can switch props and crystals in the meantime I'll look at the power and other leads with scope for noise spikes.

    Thanks again
    Ben
  • Cluso99Cluso99 Posts: 18,069
    edited 2010-09-12 21:05
    FYI... Some of the prop pcbs have xtal sockets so you masy not need to desolder. They are just socket pins and do not look as though the xtals are socketed. I know the Prop ProtoBoard (both the USB and non USB versions) have socketed xtals.
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