Thanks Dave, now im getting clearer about the "standars" on the serial ports.

So, the tweener has just one TTYSx, wich is the console right?? Or is there another tty? I ask this cause, since u said that the tweener had a level-shifter, then I may use this to interface directly some serial devices.
I need to controll over 12 servos, so that is why Im using this servo controller. Since this controller has a TTL "level", the I might be able to connect directly to a port on the gumstix/robostix, right? . Then wich port it is??
If I connect to a ttsy on the robostix, then I´ll have to program the robostix to use this port, or I can access directly from the gumstix, trought /dev/ttySx?

Thanks Dave and Jesse

2006/8/16, Dave Hylands <>:
Hi Miguel,

> > But it's pretty much imposible (maybe not impossible, I'm computer science
> not electrical engineering so maybe there is a hack i don't know about) to
> get RS-232 signals to run on TTL hardware, unless you do some kind of level
> shifting.

Unfortunately, lots of people abuse the terminology. Suffice it to
say, that if you can connect it directly to your PC and it works, then
it needs to go through some type of level conversion before it gets to
the PXA255.

The tweener and waysmall boards have built-in level conversion, but
the robostix or breakout boards don't.

So, if you're going to use the robostix (or any of the breakout
boards), then you'll need some type of level conversion, like what's
described here:

Dave Hylands
Vancouver, BC, Canada

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Miguel Pincheira Caro
Ingeniería (E) Computación e Informática
Universidad del Bío-Bío