Pulsout For Serial protocol servo.

azmax100

Hi

I've purchase an Isobot robot few week ago but yesterday something bad happen. I think because of one servo failure it has damage the main board. I am not sure how. Theres a few 3.3v regulated IC on the board which not functioning. Maybe because of the overload current.

So now I have a 17 DOF Humanoid robot that is waiting seriously for me to do something with it.

According to this blog http://i-sobothacking.blogspot.com/ the servo are driven by serial protocol which I don't even understand.

So how can i do something with BS2 or propeller?

Post Edited (azmax100) : 7/6/2009 8:07:06 PM GMT

Mike Green

First you need to find information in English about the servos. From the 'scope pictures, it seems like it is indeed some kind of serial protocol.

Without more information, it's impossible to tell whether the BS2 is capable of handling this protocol. It may be too fast for the BS2.

The Propeller could certainly handle anything up to 1MBaud.

You may have other damaged servos. If the main board is damaged, that can also damage other servos.

azmax100

Hi Mike,

As usual you are the man.

First of all can you explain in laymen what is serial protocol. I've never experience this before.
I take it positively as I am going to learn new thing. Theres a hex table in the hacking blog which I dont really understand.
Maybe I can do some homework if somebody guide me trough.

I really love this robot but just unlucky.

Timmoore

There are some servos from Dynamixel that use a serial protocol. You could look on their website for the protocol spec and compare to what you are seeing.
There is also project using a prop to drive those servos you could look at. See http://www.crustcrawler.com/motors/RX64/index.php?prod=67

azmax100

Thanks Timmoore.

You really gave me a lot of homework to do. And for sure I will ask a lot of question.

azmax100

From my early observation the different between Dynamixel and Isobot servo is Dynamixel are link by daisy chain while Isobot servo in parallel.

Is that mean anything? I am assuming that theres an ID for each servo. Is it right?

Franklin

www.isobotrobot.com/eng/more/download.html Any help here?

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
- Stephen

azmax100

I found another Japanese hacking site

http://translate.google.com/translate?u=http://robot.watch.impress.co.jp/cda/column/2007/11/08/731.html&langpair=ja|en&hl=en&ie=UTF-8
(translated to english)
that show the hex file to control the servo using uC. The baud rate is set to 2400

Can somebody guide me how to sent this command using BS2 or Propeller.

Example code are very much appreciated.

As there are hundred thousand of Isobot that are going to have faulty controller someday. this would be the beginning
of new humanoid robot using BS2 or Prop.

Franklin maybe you can help me now. BTW thanks for that.

Mike Green

With a BS2, you would use: SEROUT <pin>,396,[noparse][[/noparse]255,5,one,two,three,four,five,5+one+two+three+four+five]

one, two, three, four, five are the names of byte variables that contain the servo position information with 128 being center. That's all I can figure out from your Japanese hacking site. <pin> is the I/O pin number you want to use. I don't know what signal voltage your servo expects, but you might put a 1K resistor between the Stamp I/O pin and the servo control pin in case the servo expects a 3.3V logic level since the Stamp supplies 5V.

You'll need to download and read the Basic Stamp Syntax and Reference Manual for further details on Parallax's Stamp Basic: www.parallax.com/tabid/440/Default.aspx.

azmax100

Thanks mike for showing the way.

I really appreciated for the time you put in reading the blog and explaining to me.
Theres no excuse for me for not doing the experiment now. I will let the forum members know the outcome.

azmax100

I have success in moving the left leg using Pin 8 from BS2 and use the Serout command.

Its a long way to go to make him walk but at least there are possibilities.