Arduino to Unity Project Part 6: From zones to direction vectors

In my previous implementation of the Arduino directional input to Unity I divided the scales of the Y and X-axis ranges and gave each zone a number 0-8. This way I only needed to send that number over Serial to Unity. But that also meant that I only could input 8 directions(+ 0 for standing still). After doing some state of the art research I decided that this was not enough. I wanted to be able to input any direction(360 degrees).

To do this we can picture the the analog stick in a coordinate system where the rested position of the thumbstick is in the origo(x1, y1). If I then move the thumbstick in any direction that is going to change the potentiometers value so that I get an x2, y2 position.

v = x2-x1, y2-y1 then then gives me a vector which goes from origo to the new position of the controller. And if I normalize that vector I get a directional vector which is vector of length one that describes a direction. I could then use Unitys tranform.Translate()-function to move an object in that direction in real time, following the user input of X and Y values over the serial port.


Setting up a coordinate system.

First I had to reverse the range of the X-axis from the thumbsticks horizontal potentiometer. For some reason it was made so that the vertical scale was growing upwards but the horizontal scale was growing to the left. To get this to work as a conventional coordinate-system I needed to reverse it so that the X-axis was growing to the right.

For some reason the horizontal scale grows to the left?

Next I calculated the delta X and delta Y. Now the axis range from -510  to  510 with 0 in the middle.

Sending data over serial

Previously I only needed to continuously send number over the serial port to Unity. I could do that with Serial.write() in the Arduino IDE and read it with ReadByte() in Unity. So I was sending one byte with each package. However, 1 byte can only hold a value 0-255. My values where between -510 and 510 and both for the X and Y axis which meant it would no longer fit inside a byte. From reading online it seems possible to send multiple bytes with the Serial.write()-function, however I am not sure how I would receive that without knowing the exact number of bytes sent. I could also try to split the data up into several packages but that would require some algoritm to check when all the parts of a package has been received. Instead I used the Serial.print()-function which prints "Prints data to the serial port as human-readable ASCII text." as it says in the Arduino documentation. I sent the X and the Y value seperated by a "," and then I could use ReadLine() in Unity and then split and parse to get the values. This certainly does not seem like the most elegant method of sending numerical data(converting int to string, converting back to int) but I am yet to find a better way nor anyone else who have done it. Truth is that information on Arduino to Unity Serial communication is quite limited online.

I wrote a C#-script in Unity to read the serial data, split and parse it to X and Y valuebles. Then I created a Vector3(X,0, Y) and normalised it to get a directional vector to describe the direction that I wanted to move the character (in this case the Unity FPScamera). This scrips seemed to work fine. However I had some problems with the serial communication. It seemed that there was a sync problem between the arduino sending code and the unity receiving. My theory is that ReadLine() takes longer than ReadByte() which is why the serial connection are not as direct (write -> read). This causes a async problem. I had to play around with delay(ms) on the Arduino side and ReadTimeout() on the Unity side to make them sync a little bit better. However, if the delays where too high that would gravely affect frame rate in my Unity scene. I finally found out that 4ms delay in arduino and 5ms ReadTimeout() in Unity seemed to work OK. I also had problems with Unity sometimes not parsing correctly and I have a lot of different exceptions when running. I need to optimize the code. But this is the version I have at this point:

Arduino to Unity: Thumbstick X, Y coordinates to calculate exact direction vector from Evert Lagerberg on Vimeo.

It works OK. Framerate is about 60 FPS and acceptable. It is now possible to move in any direction instead of just 8.