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Simone Seagle

Simone Seagle

Independent Web and Educational Software Developer

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Fall Ball Updates
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Fall Ball Updates

April 25, 2016 Simone Seagle

I've gotten my Fall-Ball project to the point where it's plotting the data in real time!

For some time now I've had the KL46Z successfully broadcasting its accelerometer data out using a Bluetooth dongle. The code to do that was pretty simple, and it also shows how the data was formatted.

int main()
{
    init();
    while (true) {
        if (timer.read() > UPDATETIME) {

            // Read the acceleration on all three axes
            float accData[3];
            accelerometer.getAccAllAxis(accData);

            bluetooth.printf("x:%f y:%f z:%f\n\r", accData[0], accData[1], accData[2]);

            // Just show the x acceleration on the LCD screen for debugging purposes
            sprintf (lcdData,"%4.2f", accData[0]);  

            LCDMessNoDwell(lcdData);

            timer.reset();
        }
    }
}

I used Node.js for the server so I could read the Bluetooth serial port. There's a sweet little serial library that you can install with npm that works really nicely. My first implementation of the program used Python, which was kind of a pain because there's no timer built in AND the python serial library doesn't have events. I wanted this program to be event-driven so that the end-user would have a better experience.

The code to parse the data from the serial port is also fairly simple:

// When the serial port gets data, parse it and send it out to the clients as an object with properties for x, y, and z
fallBallPort.on('data', function(data) {

    var x_acc, y_acc, z_acc;
    var acc = data.split(' ');

    if (acc.length != 3) return;
    x_acc = acc[0].substring(3, acc[0].length);
    y_acc = acc[1].substring(2, acc[1].length);
    z_acc = acc[2].substring(2, acc[2].length);

    console.log("x:"+x_acc+", y:"+y_acc+", z:"+z_acc);
    io.sockets.emit('data', {x:x_acc, y:y_acc, z:z_acc});
});

I use the Node.js socket.io library to send data out to all the clients. Right now I'm running in on my computer, but shortly I will be installing all this on a Raspberry Pi.