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AppMod-compatible devices? — Parallax Forums

AppMod-compatible devices?

CounterRotatingPropsCounterRotatingProps Posts: 1,132
edited 2008-07-22 01:53 in BASIC Stamp
Greetings!

several N&V articles, for example #144, mention·a "Parallax AppMod-compatible device."

A search here turns up a lot about header pin outs, but not much about a spec. per se. The products pages and catalog don't mention such devices (of course, I could have missed seeing such! shocked.gif).

Could you all describe this, or point to·a link about the concept?

thanks!


·

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2008-07-10 00:27
    The Board of Education has a connector on it known as the AppMod connector. It's a 20 pin female header that provides the 16 I/O pins and power. There are only a few devices that use it. Look at the schematic for the Board of Education for the wiring.
  • CounterRotatingPropsCounterRotatingProps Posts: 1,132
    edited 2008-07-10 00:34
    Wow! thanks much for the quick reply.

    >> Look at the schematic

    thanks, yes I will do that.

    >> only a few devices that use it

    Where might we find these?

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  • Mike GreenMike Green Posts: 23,101
    edited 2008-07-10 00:49
    You find them by browsing the Parallax web store. The EB500 Bluetooth adapter is one. There's a CMUcam that uses it and I think there's still an LCD display. That may be all.
  • CounterRotatingPropsCounterRotatingProps Posts: 1,132
    edited 2008-07-10 01:01
    Ah! there are more items here than the catalog - doh! Thanks for the list - between the schematic at these items, I should be able to figure it out. It's always better not to re-event the ox cart...

    wonder why the app-mod format is not more widely used?

    thanks again for the fast reply!

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  • CounterRotatingPropsCounterRotatingProps Posts: 1,132
    edited 2008-07-13 22:33
    A follow up...

    from what I've read in the mean time,·it seems·that App-Mod is not only a pin out config, as Dr. Green mentioned, but also a Protocol.

    Since Parallax has the header on board, is·the AppMod protocol is a Parallax-defined communication protocol and·is·it documented somewhere here? - it's hard to imagine its proprietary!

    thanks
    -Howard

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  • Mike GreenMike Green Posts: 23,101
    edited 2008-07-13 22:50
    The closest thing to a protocol is the use of an asynchronous serial connection where the commands begin with "!xx" where "xx" is a two letter combination unique to the device, followed by some kind of data, followed by a return character. This is also used with other kinds of devices, like the Parallax Servo Controller.
  • CounterRotatingPropsCounterRotatingProps Posts: 1,132
    edited 2008-07-17 00:28
    Ah ha! very good (and terse [noparse]:)[/noparse] clarification!

    Did Mr. Williams create this idea - he mentions it so frequently in his Nut's and Volts articles (including fairly recent ones) that I assumed this was a widely accepted protocol. Nonetheless, it does seem like a clever solution. I'll be doing a far amount of R&D with RS-485 - it seem natural to adopt any standard already supported.

    thanks,
    -Howard

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  • Mike GreenMike Green Posts: 23,101
    edited 2008-07-17 00:36
    The scheme comes from the desire to start a command with a fairly unique printable character (like "!") which is easy to look for (with a WAIT("!") formatter in a SERIN statement or its equivalent) followed by a unique device identifier (as long as there's only one such device connected). You can follow that with any necessary parameters, usually in printable form (and displayable too), then a return character to end the command line. This is all easy to implement with a Stamp or pretty much any microcontroller and pretty foolproof.

    I have no idea who came up with it first at Parallax. It's not a new or unique idea, just nicely done.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2008-07-18 16:10
    There are actually two components to something being AppMod compatible as far as protocol. Not only do the devices send an identifier which is often !xx but they must use OPEN Baud mode so that the serial line is not driven when idle. This allows multiple devices to exist on the same serial line.

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  • ZootZoot Posts: 2,227
    edited 2008-07-18 19:25
    Robert Doerr also compiled a list of "AppMod" compatible boards and projects. These don't necessarily use the AppMod pin layout for a header, but all use the open serial scheme and ! header prefix. Some of these are home-brew projects, some are Parallax's, etc.

    http://forums.parallax.com/showthread.php?p=716795

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  • Andy FoxAndy Fox Posts: 46
    edited 2008-07-18 23:02
    CounterRotatingProps said...

    from what I've read in the mean time, it seems that App-Mod is not only a pin out config, as Dr. Green mentioned, but also a Protocol.

    Hey, Howard.

    Not quite sure where you read about this protocol but I have both the Modem AppMod and LCD Termianl AppMod and neither of these has any sort of common protocol. In each case you communicate directly with the hardware on the AppMod board according to that hardware's specifications, which don't follow this "AppMod protocol".

    Just wanted to let you know about this--not all AppMod boards out there have this protocol.
  • ZootZoot Posts: 2,227
    edited 2008-07-19 04:22
    Andy, while I wouldn't say that AppMod devices are a "protocol", certainly there is what be called an "traditional standard" as Chris mentioned -- all the AppMod devices (to my knowledge) communicate with the host via an open true serial line, and all commands are addressed using some kind of "!XY" header string.

    The open true (pulled high, driven low) serial line means any number of devices can all share the same serial I/O line, and the addressing schema means you can address any device on the line. It's a pretty simple and effective way of adding lots of peripherals to a project with only a single dedicated host pin.

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  • Andy FoxAndy Fox Posts: 46
    edited 2008-07-20 17:43
    Not debating that some AppMod boards use that wiring, Zoot. I am only stating that the Modem AppMod and LCD Terminal AppMod do not use the "!XY" protocol, and that the LCD AppMod is not a serial interface at all but instead uses a 4-bit parallel interface. I have written programs for both of these AppMod boards. Maybe these are the only two AppMods that don't use the "!XY" protocol. My intention was simply to alert the original poster that not all AppMod boards out there are created equal.
  • CounterRotatingPropsCounterRotatingProps Posts: 1,132
    edited 2008-07-22 01:53
    Thanks Mike, Chris, Zoot, and Andy!

    this is exactly what I wanted to know... and Zoot, the link is much appreciated. Interesting that one poster there mentinos that Parallax discontinued the appmod products some years ago, yet the most recent items are this year. It seems like a good idea at least in the sense that it might make it easier to understand someone else's code than if you were to roll your own, so to speak.

    I'll dig around in that thread a while to learn more.

    thanks again!
    - Howard in Florida

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