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MCP2510 Clock Out -> Prop Clock In — Parallax Forums

MCP2510 Clock Out -> Prop Clock In

Chad GeorgeChad George Posts: 138
edited 2009-06-09 01:50 in Propeller 1
So I'm going to be using a MCP2510 CAN bus controller ... mostly because I want a really solid bus and don't want to hassle with writing a S/W implementation right now.

The chip has a clockout with a software controlled divider and its active immediately after reset...

So I'm a little short on board space and was thinking of using this to clock the propeller, but I've never tried this sort of thing before and wanted to know if anyone else has had success with something similar.

As long as it works, the only negative I can see is that resetting the MCP2510 from the prop would result in the prop's clock changing...maybe even glitching out for a while.

I don't know how important resetting the chip might be...I usually connect reset pins to spare I/Os just in case it becomes useful, but sometimes I don't ever end up using them.

heres a link to the datasheet: ww1.microchip.com/downloads/en/DeviceDoc/21291F.pdf
Any words of wisdom?

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2009-06-09 01:30
    The Prop could switch to using its built-in (RCFAST) clock before resetting the MCP2510, then wait for the MCP2510's clock to stabilize before switching back to using it.

    When your program initializes itself, it needs to start with the built-in clock first in case the MCP2510 was just reset.

    Crystals are cheap and don't take much board space.· It would be much simpler to use a separate clock for each or even use the Propeller's clock for the MCP2510.
    ·
  • Chad GeorgeChad George Posts: 138
    edited 2009-06-09 01:40
    Mike,
    the more I think about it...you're right. The prop's crystal just isn't expensive enough to be worth the hassle.

    I might consider clocking the MCP2510 from the propeller though since that would be a lot simpler

    Is there any real difference between the propeller outputting a 20Mhz clock signal and the MCP2510 having its own 20Mhz crystal?
  • LeonLeon Posts: 7,620
    edited 2009-06-09 01:49
    There might be more jitter on the clock generated by the Propeller.

    Leon

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  • Chad GeorgeChad George Posts: 138
    edited 2009-06-09 01:50
    That might not be good for CAN bus...I hear its fickle about bit timings.
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