Trill/bar-visual/render.cpp

Trill Bar GUI

This is an example of how to communicate with the Trill Bar sensor using the Trill library. We also visualise position of each touch in real time via the integrated Bela p5.js GUI.

The Trill sensor is scanned in an AuxiliaryTask running in parallel with the audio thread and the number of active touches, their position and size are stored in global variables.

Click the GUI button to see a visualisation of the sensor. Up to 5 touches position with touch size are displayed in the sketch.

/*
 ____  _____ _        _
| __ )| ____| |      / \
|  _ \|  _| | |     / _ \
| |_) | |___| |___ / ___ \
|____/|_____|_____/_/   \_\
http://bela.io
*/
#include <Bela.h>
#include <cmath>
#include <libraries/Trill/Trill.h>
#include <libraries/Gui/Gui.h>

#define NUM_TOUCH 5 // Number of touches on Trill sensor

// Gui object declaration
Gui gui;

// Trill object declaration
Trill touchSensor;

// Location of touches on Trill Bar
float gTouchLocation[NUM_TOUCH] = { 0.0, 0.0, 0.0, 0.0, 0.0 };
// Size of touches on Trill bar
float gTouchSize[NUM_TOUCH] = { 0.0, 0.0, 0.0, 0.0, 0.0 };
// Number of active touches
int gNumActiveTouches = 0;

// Sleep time for auxiliary task
unsigned int gTaskSleepTime = 12000; // microseconds
// Time period (in seconds) after which data will be sent to the GUI
float gTimePeriod = 0.015;

/*
* Function to be run on an auxiliary task that reads data from the Trill sensor.
* Here, a loop is defined so that the task runs recurrently for as long as the
* audio thread is running.
*/
void loop(void*)
{
        while(!Bela_stopRequested())
        {
                // Read locations from Trill sensor
                touchSensor.readI2C();
                gNumActiveTouches = touchSensor.getNumTouches();
                for(unsigned int i = 0; i < gNumActiveTouches; i++) {
                        gTouchLocation[i] = touchSensor.touchLocation(i);
                        gTouchSize[i] = touchSensor.touchSize(i);
                }
                // For all inactive touches, set location and size to 0
                for(unsigned int i = gNumActiveTouches; i < NUM_TOUCH; i++) {
                        gTouchLocation[i] = 0.0;
                        gTouchSize[i] = 0.0;
                }
                usleep(gTaskSleepTime);
        }
}

bool setup(BelaContext *context, void *userData)
{

        // Setup a Trill Bar sensor on i2c bus 1, using the default mode and address
        if(touchSensor.setup(1, Trill::BAR) != 0) {
                fprintf(stderr, "Unable to initialise Trill Bar\n");
                return false;
        }
        touchSensor.printDetails();
        // noise may cause some spurious touches with very small size to be
        // detected. Silence them here
        touchSensor.setMinimumTouchSize(0.1);
        usleep(10000);

        // Set and schedule auxiliary task for reading sensor data from the I2C bus
        Bela_runAuxiliaryTask(loop);

        // Setup GUI
        gui.setup(context->projectName);
        return true;
}

void render(BelaContext *context, void *userData)
{
        static unsigned int count = 0;
        for(unsigned int n = 0; n < context->audioFrames; n++) {
                // Send number of touches, touch location and size to the GUI
                // after some time has elapsed.
                if(count >= gTimePeriod*context->audioSampleRate)
                {
                        gui.sendBuffer(0, gNumActiveTouches);
                        gui.sendBuffer(1, gTouchLocation);
                        gui.sendBuffer(2, gTouchSize);
                        count = 0;
                }
                count++;
        }
}

void cleanup(BelaContext *context, void *userData)
{}