Susana Passinhas @Fab Academy 2023

The capacitive sensor

So I started by getting back to my board and the mini board I did for the inputs week. I used a capacitive sensor (using my own body) to be the input on the circuit. A capacitive sensor is able to collect and hold a charge of energy. A capacitive circuit changes its charge if a finger touches it because the human body also holds the charge of energy, therefore the capacitive circuit will increase the charge if we touch it.

Getting the input data right

I uploaded the same code I used before, but this time I needed to get only the reading of the energy charge values, so I went ahead and removed the time and the line breaks, and so on until all I got was the value readings separated by line break.

The serial port

Now, before I went into Processing I needed to check the serial port I was using. We can only use a serial port at the time and I needed to access this data coming from the SAMD11 in my board from Processing, therefore I needed to access the serial my SAMD11 was using to send the data8.

Getting data from Arduino IDE in Processing through the serial port

To get the data from serial coming to Processing I first imported the serial library "processing.serial.*", then I defined a Serial variable "Serial myPort;" and then in my setup function, I defined the serial port address and the baud rate in the variable defined before.

Then in the loop function, I said that if the serial port was available to fetch data from it I would then translate it into a number (instead of a string), using teh function "Integer.parseInt()". I also said that the values would be read together until there is a line break (myPort.readStringUntil('\n')).

Visualizing the data

I used an example from the class to test the input with a visualization. I knew that when the capacitive sensor was not being touched when the values were around 380 and when it is touched they are above that. So I adapted the code adding an if condition saying that if the values are above 380 then the color of the rectangle was red.

Visualizing the data using a simple particle system

So, now it was time to do something close to what I could have for my final project, I wanted to have a more ethereal animation that could represent the touching in the sensor, so I used a Processing example, the simple particle system, and changed a few things.

I used the same logic has before using an if condition, but this time what changed was what was happening when touched. When touched the particle system would start, if not touched there was nothing on the screen.

I also added text, envisioning that it could be displayed as an installation inviting people to interact with it. To add the text I check this example.

I also wanted to add my litle eye icon to this project (the same one I have on my website and PCBs), so I folowed this example to add it.

For this code, we use 2 extra files, the particles, and the particle system (class that holds all the particles). In the particle file, some variables are defined so that each particle has a lifespan, velocity, acceleration, and position. Those values will create the movement for each individual particle being created.

There are 3 functions here, one to update the position (because they are always in movement), another function to display the particle (in this case it draws an ellipse), and another one to check if the particle is not viewed anymore so that we can remove it.

In the class ParticleSystem we define it. So we have a function to add particles (the same ones defined before) and position and for how long this system should run (otherwise it keeps on filling the screen with particles).