Thanks goes to the kind folks at mindsensors.com for sending me their new PSP-Nx Sony PlayStation 2 controller interface for the LEGO Mindstorms NXT. I wanted to give the interface a spin and post a review, so I put together a simple robotic vehicle that I affectionately call the Tourist (click here for hi-res). Is the PSP-Nx a stud or dud? See the full review after the jump to find out!

I’ve always wanted a way to remotely control my LEGO Mindstorms NXT creations. The most popular option available thus far has been the use of second NXT set to act as a Bluetooth remote. It’s certainly a very cool way to get the job done (and pure in terms of NXT-only parts), but it’s probably not a cost-effective option for folks who have already plunked down the $250 for their first set. Free alternatives include Microsoft Robotics Studio and a few homebrew projects, but they are currently in their infancies and may each have a bit of a learning curve.

The mindsensors.com PSP-Nx is now available and, at a mere 35 bucks, it provides an easy and inexpensive remote control solution for NXT fans on a budget. The interface is said to support any Sony or third-party compatible PS2 controller. I picked up a Pelican 2.4 GHz wireless controller for about $20 at a local game store.

A standard PS2 controller has two analog joysticks and 16 buttons — all of which can be read by the PSP-Nx. I have heard that the two rumble motors within the controller can be programmed to provide force feedback, as well. Speaking of programming, the PSP-Nx is currently only supported by RobotC and NBC. With the imminent release of the LabVIEW toolkit, however, I expect an NXT-G block for the PSP-Nx to shortly follow. In the interim, you can use the ultrasonic sensor block, but functionality will be limited.

The terminal connector of your controller or wireless receiver plugs right into the PSP-Nx, which can then connect to any of the four sensor ports on the NXT intelligent brick. When the interface is turned on, a nifty LED indicator lets you know if you’ve connected your controller terminal improperly. Learn to use this indicator as installing the controller terminal can be tricky at times. The PSP-Nx uses a standard RJ-12 connector accepting a center latch, so a converter cable is provided to connect to the NXT’s proprietary port.

Unfortunately, I can’t say I’m a big fan of how the interface mounts onto the NXT. The PSP-Nx is a raw circuit board with two pairs of mounting holes set three Technic modules apart. First off, the circuit board has the depth of a stud, so you have to use hybrid connectors which don’t really yield a secure mount (I like to crash into things). Secondly, call me anal retentive, but a distance of three modules makes it a little difficult to achieve symmetry along most beams. Hey, don’t let all this scare you, though. The benefits of remote control far outweigh these minor physical issues.

Ready to give the PSP-Nx a shot, I built the Tourist. It’s nothing sophisticated. Rather, it’s a simple vehicle where two motors drive the rear wheels and the third motor controls the front steering wheels (sorry, no rack and pinion). The ultrasonic sensor gives it a jeepy look but could prove to be more awesome if force feedback is sent to my controller when it encounters obstacles.

Programmed in RobotC, the Tourist uses the left and right analog joysticks to control steering and acceleration, respectively. I mapped motor power levels to the values returned from the sticks to take advantage of their full ranges. Thus, movement is not a matter of stop and go, but a gradual increase or decrease in acceleration like it should be. It was easy and worked out well.

Remote control was straightforward. After compiling, I set the Tourist down, ran my program, and enjoyed the freedom of controlling my new creation. The wireless range, although a function of your controller and not the PSP-Nx, was spectacular. The sky’s truly the limit with the PSP-Nx and it’s probably the best addition to any LEGO Mindstorms NXT set.

Good:
Look Ma, no wires! It’s absolute remote bliss at an affordable price.
Supports all 16 buttons and both analog joysticks.

Not so Good:
Does not currently support NXT-G.
Questionable mounting mechanism.

Verdict:
The PSP-Nx is a stud. Despite a few minor issues, it’s a must-have for any NXT fan yearning for remote control.