serial port servo control

[boyle5]

So I ordered a mini SSC II (the servo controller), in order to
control some servos from the computer.  I was hoping to use python to
do the control but have two questions...

1) How should I write to the serial port with python? I found the
module "pyserial":
http://pyserial.sourceforge.net/
on the python cheeseshop, and it looks solid but I thought you might
have a better suggestion.

2) To control the servos I have to send the SSC II a string of 3
numbers, 3 bytes long (so 3 numbers in the range 0 - 255, each as a
single byte, one after another).  In C I'd do this by sending 3
char's, as they're only 1 byte, but i'm not exactly sure how to do it
in Python.

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Re: serial port servo control

[Diez B. Roggisch]

[EMAIL PROTECTED] schrieb:
> So I ordered a mini SSC II (the servo controller), in order to
> control some servos from the computer.  I was hoping to use python to
> do the control but have two questions...
> 
> 1) How should I write to the serial port with python? I found the
> module "pyserial":
> http://pyserial.sourceforge.net/
> on the python cheeseshop, and it looks solid but I thought you might
> have a better suggestion.


pyserial is what you need.

> 2) To control the servos I have to send the SSC II a string of 3
> numbers, 3 bytes long (so 3 numbers in the range 0 - 255, each as a
> single byte, one after another).  In C I'd do this by sending 3
> char's, as they're only 1 byte, but i'm not exactly sure how to do it
> in Python.

Strings in python are byte-strings. So you can use them. Additionally, I 
recommend looking into the module struct.

Diez
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Re: serial port servo control

[Richard Brodie]

<[EMAIL PROTECTED]> wrote in message 
news:[EMAIL PROTECTED]

> 1) How should I write to the serial port with python? I found the
> module "pyserial":

I don't think there is any need to hunt for anything better.

> In C I'd do this by sending 3 char's, as they're only 1 byte,
> but i'm not exactly sure how to do it in Python.

Use a string type. output = chr(x) + chr(y) + chr(z)  for example.
There is no restriction on null bytes in strings, so they are
appropriate for binary data. 


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Re: serial port servo control

[Si Ballenger]

On 22 Jun 2006 08:18:08 -0700, [EMAIL PROTECTED] wrote:

>So I ordered a mini SSC II (the servo controller), in order to
>control some servos from the computer.  I was hoping to use python to
>do the control but have two questions...
>
>1) How should I write to the serial port with python? I found the
>module "pyserial":
>http://pyserial.sourceforge.net/
>on the python cheeseshop, and it looks solid but I thought you might
>have a better suggestion.
>
>2) To control the servos I have to send the SSC II a string of 3
>numbers, 3 bytes long (so 3 numbers in the range 0 - 255, each as a
>single byte, one after another).  In C I'd do this by sending 3
>char's, as they're only 1 byte, but i'm not exactly sure how to do it
>in Python.

Maybe a little off topic, but I've got a page below with some mini ssc
control info.

http://www.geocities.com/zoomkat/index.htm

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Re: serial port servo control

[Scott David Daniels]

Several have suggested struct, I'd suggest you look at array:
 import array
 v = array.array('B', [1, 2, 3])
 for i in range(17):
 v[i % 3] *= max(1, i // 3)
 v.tostring()

--Scott David Daniels
[EMAIL PROTECTED]
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