NXT-Spy – A stable connection between the phone and the robot (finally!)

While I was testing the robot in its environment, the Bluetooth connection between the phone and the robot stopped working for a reason I still can’t figure. To solve that, I decided to go find on internet any person who worked with LeJOS NXJ from an Android phone over Bluetooth, and I found the perfect solution on a forum : NXTCommAndroid [source]. This developer actually ported completely all the comm package from the PC LeJOS API to Android. I implemented it and it worked perfectly on the first try! I also figured out that he posted it on the 9th January so less than 1 month ago.

Even further, this portage may allow me in the future to control completely the robot from the phone and avoid having any code other than the Bluetooth receiver on the robot…

NXT-Spy – Fixes on the flag coordinates processing and of the output of the coloured ball processing

In order to get the coordinates of the flag from the flag processing library (zxing), we are using a function called getResultPoints() on the result object outputted. The problem is that this function only outputs three points, from now on I supposed it was the top left, top right and bottom left coordinates of the flag, but actually, I just figured that it is more complicated than that.

In fact, the flag processing only provides us the coordinates of the “target style” points we can find on any QR code in a random order. The problem is that to be able to get precisely the flag position, we need first to find the coordinate of the fourth corner of the flag and then to get the smallest rectangle in which all the points can fit corresponding to the flag’s position.
That’s why today I added to the flag processing process a function that calculates and draw the two rectangle involved in the process as shown on the image below:

Assuming we have a triangle ABC made from the three QR points placed randomly (their order can change if we rotate the flag), the first step is to find the biggest side of the triangle (AC in this example), we then find its centre (D in this example). We then calculate the symmetric point of B centred on D (E in this example), it is the fourth point we were looking for and we can now calculate the coordinates of the red rectangle quite easily thanks to the java.awt.Rectangle add function (a function that adds points to a Rectangle object and outputs the smallest rectangle that includes all the points passed to it).

Now, the flag processing is more accurate and works for any inclination of the flag, an other good thing is that now it outputs a java.awt.Rectangle instead of an array of points.
After done all that on the flag processing, I thought that it could be interesting if the coloured ball processing could also output a Rectangle object instead of ukdave’s BoundingBox object. BoundingBox and java.awt.Rectangle being quite similar, I quickly did the modifications in the coloured ball processing process code and so now everything is more standard: the two image processing coordinates output are a java.awt.Rectangle object.