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Differences between MCP3208 and MCP3208 Fast objects — Parallax Forums

Differences between MCP3208 and MCP3208 Fast objects

RobotWorkshopRobotWorkshop Posts: 2,307
edited 2012-01-27 14:02 in Propeller 1
I've have used the MCP3208 object in my current project and was wondering how it compares to the MCP3208 Fast object in the OBEX. Are the two objects completely interchangeable? If you've used both which one works better and is the Fast version that much faster?

Comments

  • Duane DegnDuane Degn Posts: 10,588
    edited 2012-01-27 08:42
    I know I've used them both.

    I think the main difference between the two is one uses Spin and the "Fast" version uses PASM.

    I think I ran some speed tests once but I don't remember the details. I'm pretty sure the fast version is a lot faster but it does cost a cog to have the PASM driver running.

    The Spin version doesn't use an extra cog.

    Edit: I'm not positive about what I just wrote. I'll need to look at the original objects to make sure. I had been looking at objects I had modified.

    Edit Again: I wont delete this post, but it would probably be a good idea to ignore what I wrote above. I have a much slower Spin only version. I think I wrote it myself (I think it's a modified version of a LTC1298 driver I found). I see now the original MCP2308 by Chip uses PASM also.
  • Bobb FwedBobb Fwed Posts: 1,119
    edited 2012-01-27 10:58
    If you need really fast, you should use this one: http://obex.parallax.com/objects/488/ because it continually populates usable variables rather than querying the ADC each time you need a value (it also has a lot of other features the other two don't have). It uses a cog, and isn't a drop in replacement for anything (though it is easy to implement).
  • RobotWorkshopRobotWorkshop Posts: 2,307
    edited 2012-01-27 11:40
    Thank you both for the responses. I believe that the regular MCP3208 object is using s COG so that won't be a problem. I may try the MCP3208 Fast version this weekend since it sounds like it may drop right in place with very little changes. I didn't see that other object but will keep that in mind as well. At the moment I'm just using this to monitor an Audio line which then in turn controls some LED lighting.
  • max72max72 Posts: 1,155
    edited 2012-01-27 14:00
    I had problems with the faster objects and a "loose" setup.
    In my case the slower object was more forgiving, while Bob Fwed's was way too fast for my setup.
    So if you want to go fast be careful with wiring and routing.
    Massimo
  • Bobb FwedBobb Fwed Posts: 1,119
    edited 2012-01-27 14:02
    There's a new "slow" mode setting in my program that slows the communication to the ADC to below datasheet specifications, but still populates the variables.
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