Nunchuck and NXT

[Ben Axford]

Hi all,

I am trying to get a project going to connect the NXT directly to a Nintendo Wii nunchuck.

The idea is to build a nice labview created interface for the nunchuck, because the nunchuck has the following features

3d accelerometer

Joystick

at least i Pressure sensitive button.

All this for one connection to the NXT, and hopefully not too much electronics in between.

This is what I have found out about the hardware interface for the nunchuck

I2C protocol - from what i can gather from the internet, it uses a 'Fast' protocol - 400 kbaud or something like that.

not sure about the voltages required at the moment. Current Gameboy connection cables could probably be used to hack a reasonable connector to the nunchuck though.

From what i have been able to work out about the NXT, it too uses i2c - but at 9600 baud. therefore I am guessing that this won't work.

However, it appears that port 4 also supports rs485 - and speeds up to 920kb.

Also in the labview documentation, there is an enumeration for 'sensorType' - and Value 0x0C is 'Highspeed'. anyone experimented here? I imagine that this may be only for port 4, but hope that it could be a highspeed i2c mode.

So i am wondering whether anyone knows how difficult what I am talking about would be?
Has anyone mucked around with Nunchucks directly through I2C, or only through hacking remotes?

How difficult is it to interface i2c as rs485?

Would I need some Ic's or just a few passives?

[BradyDuggan]

I can try and clear up at least one question quickly. The NXT does have the ability to communicate using RS485 protocol through port 4. However, the RS485 protocol interface is not available through the LabVIEW programming language at this time. Since none of the sensors that ship with the kit use RS485, we didn't end up finishing out the API from the LabVIEW level for the MINDSTORMS NXT 1.0 product. The "Highspeed" enum value is unfortunately just a placeholder for now.

Also, you might want to talk to the guy who did this, as he is also trying to interface the NXT with the Wii-mote: http://www.techeblog.com/index.php/tech-gadget/wiimote-controlled-robot

Brady Duggan
National Instruments

[JohannS]

Look at this post on using a wiimote in LabVIEW. It doesn't support the nunchuk yet, but it might be interesting still. Maybe this can help in your search to control the NXT.

Hope this helps,

JohannS