How to connect parallax servo controller to PC/PDA?
lunarknight
Posts: 13
Instead of buying a usb servo controller when I have two perfectly good parallax servo controllers... Is there some way I could hook up the servo controller to some sort of usb adapter so I can power/send commands from a PC/PDA?
Comments
The software would then just be opening a com port on Linux or windows using C++ or using the MSCOMM ctrl in vb. I heard the evb and vb.net comm cntrls for PPC suck though, so I'd stick with Linux or EVC at least.
This is all theory...I've used setups broadly similar to this before, but never this situation, with a servo controller at the other end...I have no idea if it would work though I do believe the theory is sound....
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Bricknell
Carpe Noctem
··· Though I haven't drawn the schematic for this yet, you should be able to connect the TX(PC) to the serial I/O connection of the PSC via a single NpN transistor.· To power the PSC and the transistor, you would need to supply a regulated 5VDC.· Of course, the serial commands would· remain the same, so you could use Hyperterminal or any terminal-esque application to send commands to the PSC.
··· When we·release the PSC Interface software, I will post an app-note showing how to use it with the original PSC.
John B.
I just purchased a couple of PSC's and·didn't know that PSC software was being developed, will you give us an idea of when the software will be released?
Thanks,
Tim
We don't give release dates. Why? Well, when our engineering staff are also tasked (and happily so) with supporting customers, it's harder to predict dates. And when those predicted dates are missed, people get disappointed, put pressure on us ... you see where I'm going. When it's ready for public release we will make a very big deal out of it. I've seen what John is working on and it's pretty darned cool.
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Jon Williams
Applications Engineer, Parallax
Dallas, TX· USA
I understand what you are saying and why, and I knew that when I asked the question - I was just hoping for a rough idea of when the release might be.· If it's soon, I'll wait for your product for PC-based servo control, otherwise I'l like to find something simple to use in the mean time.
Tim
·· Don't hold us to it, but I believe we will have everything ready to go early March.· Jon is correct about released dates being a double-edged sword - they can hurt as much as they help, but I'm pretty confident with my estimate.· Here's a sneak preview of the software for forum members only, please do not share it with others.
· There are a few changes left that I must make. For example, I will be changing the word "ramp" to "rate".· I welcome comments and suggestions.· Please email them to: jbarrowman@parallax.com
John B.
Your reply is very generous, thank you very much for all of the information about what is upcoming for your PSC/PC control·interface.· That looks like a bunch of grins to work with and I look forward to it.· Don't worry, I won't hold you to anything and I understand how a release date would be double-edged, but it is nice to have a rough idea of the March timeline.· I'll study the screenshot closely and see if I can offer anything.
Thanks again,
Tim
when you say: "you should be able to connect the TX(PC) to the serial I/O connection of the PSC via a single NpN transistor." It seems to me you must be referring to this section of the schematic from the PBASIC SYNTAX guide that shows one how to make an adapter for the BS1 to the serial port of a PC. I have highlighted the important section that should work just as well for connection to the PSC.
correct yes?
-Steers
A great inferrence on your part. Yes, that should work just fine. The schematic I plan on posting will look similar, but I think you may wish to tweek the resistor values a bit as they may not be optimal for the PSC. Additionally, the receive side still needs supporting for bidirectional comms.
John B.
Well i'm very interested to see your schematic then as I havent got a clue as to how to do bi-directional comm (I better start doing some reading on that point) .
I just got my PSC in the mail on monday and am planning to use it with a laptop running Win95 and programming it with winbatch. http://www.winbatch.com
It will be used to guide very small ( AWG 42) magnet wire onto a transformer bobbin in a winding machine I am building. Hopefully if it all works it will provide me with much better resolution than my last winding machine which I built to use stepper motors to guide the wire.
Let me know if you need any custom wound transformers or coils....
Thanks,
-Steers
Bidirectional comms is not necessary to accomplish what your after, but it is good to have. That way, the controller could get an intelligent response from the servo controller and "know" that it's out there and functional. Within two weeks I will write the AppNote and make a nice drawing depicting just how to do this.
It sounds like you are working on a pretty cool application. I am always interested in hearing about the different ways people use our products.
Re the custom wound transformers - wow, thanks a cool offer! I am working on a couple of new products now that require such devices, but I am not allowed to spill the beans this early. Can you provide a link to a website, or email me a PDF of a catalog? If so, send it to: jbarrowman@parallax.com
Thanks!
John B.
I've ordered the serial version of the servo controller (a few days ago), and I'm planning on using it for a pan/tilt mechanism for a camera, and later as a servo controller for a foam cutting machine.
What I've been doing is using the RXTX open source serial communications library for Java...so far it seems fairly easy to use (compared to C++ serial communications) and allows me to use Java for rapid development. At this point the servo controller hasn't arrived, so I've just been working on a simple controller program that should work, given the relatively simple nature of the communication protocol it uses.
The URL for the RXTX library is RXTX.org.
Regards
George Walker
To let you know I finally did get a chance to build the interface, although i had to substitute 12k resistors in place of the 10k's as i was out of 10k's. It makes a nice 0 to 5v square wave at the input to the PSC out of the +and - 7.88volts that my laptop puts out. So far I am only using the transmit section. But it works flawlessly.
The reaction time even at 2400 bps was very fast and i dont think i'll even need to go to the higher setting.
I'll post some pictures of the winding machine in action as soon as i get the software more developed, along with some source code of winbatch subroutines that i know work to move the servo.
I'd be interested to see the foam cutting machine or the pan tilt mech if you have any pics.
-Steers
I'm currently building a PC interface using a MAX3232 chip, as I want to have bi-directional communication to the controller. I happened to have some 3232s, the MAX232 or similar would also work. Next step is get some 0.1 caps as I will need that to complete the interface.
Regards
George