Playstation robot controller

Owen

Has anyone built a playstation robot controller from the January 2006 nuts and volts article by John Williams? I'm curiouse if the pull up resistors on the Data and ATT pins are actualy needed? Also I want to use it with the propellar chip so is the pull up resistor on the SERIAL I/O line needed?
www.parallax.com/dl/docs/cols/nv/vol7/col/NV129.pdf

I guess I don't understand why it's needed when both the playstation controller and the sx28 are both 5v devices

Thanks,
Owen

Franklin

Pull up resistors are there to guarentee the pin is in a known state when the stamp is not controlling it. otherwise a line could 'float' and be in an unknown state if it were to be read.

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- Stephen

Owen

why use the external pull up resistor instead of enabling the internal pull up resistors in the SX chip?

Owen

Beau Schwabe

Owen,

The Sony Playstation controller is a bi-directional open collector data device. This means that the bi-directional lines (data and attn) need to have a pull-up
resistor in order to function properly and to avoid accidental power and ground collisions. (i.e. if the Stamp or SX were wanting to make the line HIGH and
the controller wanted to make the line LOW, then there would be a short circuit between power and ground). Signals that are not bi-directional are the Clock
and Cmd... from the Stamp or SX's point of view, they are always configured as outputs.

You could probably use the internal pull-up resistors within the SX, however these are usually considered weak pull-ups (weaker than 4.7K). Weak pull-ups
can limit communication speed causing data failures. This may or may not have an impact with the Sony Playstation controller, I'm not sure myself.

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.