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How to control the Parallax servo controller? — Parallax Forums

How to control the Parallax servo controller?

DominatorDominator Posts: 1
edited 2005-04-02 06:59 in Robotics
Hello!

I´d like to be able to control servos using the Parallax servo controller using my·PC´s RS-232 serial port.
The goal is to have a VisualBasic program controlling the servos.
Will it work if i simply connect it to th PC ?
As I understand it, the servocontroller has a single bi-directional serial port.

I´d appreciate any help here!

Best regards

/// Martin ///
·

Comments

  • Paul BakerPaul Baker Posts: 6,351
    edited 2005-03-21 14:10
    My understanding is that Parallax is in the process of developing a servo controller board that they are currently writing a PC interface for (they have posted interim screenshots). Though they will not provide an exact realese date for it, it appears to be quite far along in its development cycle so it shouldn't be too much longer (on the order of a few months at most)
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-03-21 14:44
    We have USB version of the PSC that will be aviable shortly, and we will include directions for connecting the other PSC to a PC (serial port) as well.

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    Jon Williams
    Applications Engineer, Parallax
    Dallas, TX· USA
  • SnowZeroSnowZero Posts: 2
    edited 2005-04-02 04:52
    JW: By that last bit I'm assuming you mean it is possible to connect the PSC to a computer. Could you maybe enlighten us with a hint or two on how we might get this working?

    I bought a PSC a few days ago, assuming that since I had logic level serial available, I'd be able to send to it. However that seems to not be the case. All I can do now get the serial LED to blink, but it doesn't seem to get any of the commands. Most notably I've tried 2400N1 and 2400N2 so far with no success. At this point I'm wishing I'd bought a a Mini SSC-II, but I hope I'm eventually wrong.

    P.S. I'd have waited for the USB version but my robot has to compete in two weeks...
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-04-02 05:40
    SnowZero,

    ·· Are you having trouble sending commands to the PSC via the PC, or the BS2?· What power supply do you have going into the PSC?· The logic side will get it's power from the BOE if connected to one via the servo cable.· But the servos require power through the screw terminals on the PSC.· Just curious what you have connected there.



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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • SnowZeroSnowZero Posts: 2
    edited 2005-04-02 06:52
    Wow that was quick [noparse]:)[/noparse]

    I have a rough circuit diagram attached (sorry for no pin#'s, it's from memory). Things appear to all be working except for setting any commands. The PSC is indicating power and drives all the servos to neutral as expected. When I send serial the green LED blinks. The PSC's circuit diagram shows that the green LED indicates 0 for the TTL serial (I think), which matches what you would expect when sending all 00 or all FF in hex. So I think everything is fine except my translation of the serial interface; I'm pretty certain the command message is correct, but I couldn't find what the serial paramaters should be exactly. It looks like 2400,8N1 from the docs, but that doesn't seem to work. Maybe it expects an inverted signal (0=5V,1=0V)?
    circuit.png
    512 x 373 - 17K
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-04-02 06:59
    SnowZero,

    ·· Actually, as per the docs, the device defaults to 2400bps, no parity, eight data bits, two stop bits, true data open drain (driven low, pulled high).· You must use the AppMod protocol to talk to the device.· I would suggest downloading the most updated datasheet for this device from our website.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
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