Camera-based touchscreen input via an FPGA

piano-hero-uses-camera-based-touch-input

[Chonggang Li] wrote in to share a link to the final project he and [Ran Hu] built for their embedded systems class. It’s called Piano Hero and uses an FPGA to implement a camera-based touch screen system.

All of the hardware used in the project is shown above. The monitor acts as the keyboard, using an image produced by the FPGA board to mark the locations of each virtual key. It uses a regular VGA monitor so they needed to find some way to monitor touch inputs. The solution uses a camera mounted above the screen at an obtuse angle. That is to say, the screen is tilted back just a bit which allows the images on it to be seen by the camera. The FPGA board processes the incoming image, registering a key press when your finger passes between the monitor and the camera. This technique limits the input to just a single row of keys.

This should be much simpler than using a CCD scanner sensor, but that one can track two-dimensions of touch input.

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MSP430 touchscreen piano

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[Rohit Gupta] wrote in to share this touchscreen piano project he built around the TI Launchpad. It provided a way for him to explore using a resistive digitizer found on a lot of mobile devices. These are simply stuck to the top of LCD screens and replacements are inexpensive, but salvaging one from old hardware is an option as well.

The first thing he did was to test the four outputs of the digitizer with his multimeter. Logging the changing resistance will help make sure you’re reading the correct wires and are able to zero in the settings before you start coding. [Rohit] uses the ADC on the MSP430 chip to read from the screen. He went with the algorithm from one of TI’s app notes to convert the readings in to X and Y coordinates.

He separated the screen into seven columns, each generating a different tone. Touching higher or lower on that column will alter the pitch of the note produced. You can hear an example of this in the demo after the jump.

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ASETNIOP chorded typing with a piano keyboard

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We don’t know if typing your Facebook updates from a piano keyboard counts as practicing or not. But if you want to give it a try here’s how. [Zach] wrote in to our tips line with his latest ASETNIOP hack which uses a MIDI piano keyboard to touch type on a computer.

Last July was when we first heard about ASETNIOP. It’s a chorded typing system which at the time was aimed at, but not limited to, touch screen devices. This version gives a pretty good idea of how the system actually works. Your fingers and thumbs are each assigned a key and they never move away from it. To type more than just the ten letters, combinations of keys are assigned the rest of the alphabet. You can see the piano example of the system after the break. But better yet would be hooking your own MIDI keyboard up to the computer and trying it in a browser.

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Pair of musical hacks use sensor arrays as keyboards

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This pair of musical keyboard hacks both use light to detect inputs. The pair of tips came in on the same day, which sparks talk of consipiracy theory here at Hackaday. Something in the weather must influence what types of projects people take on because we frequently see trends like this one. Video of both projects is embedded after the jump.

On the left is a light-sensitive keyboard which [Kaziem] is showing off. In this image he’s rolling a marble around on the surface. As it passes over the Cadmium Sulfide sensors (which are arranged in the pattern of white and black keys from a piano keyboard) the instrument plays pitches based on the changing light levels. [Thanks Michael via Make]

To the right is [Lex's] proximity sensor keyboard. It uses a half-dozen Infrared proximity sensor which pick up reflected light. He calls it a ‘quantised theremin’ and after seeing it in action we understand why. The overclocked Raspberry Pi playing the tones reacts differently based on distance from the keyboard itself, and hand alignment with the different sensors.

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Fruit piano uses a different circuit than the Makey Makey

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[Hasbi Sevinç] is using perishable goods in his electronics project. The orange, tomato, and two apples seen above act as keys for the virtual piano. The concept is the same as the Makey Makey which is often demonstrated as a banana piano. This implementation uses an Arduino to read the sensors and to connect to the computer running the piano program.

You can see there’s a fair amount of circuitry built on the breadboard. Each piece of fruit has its own channel to make it into a touch sensor. The signal produced when your finger contacts the food is amplified by transistors connected in a Darlington pair. That circuit drives the low side of a optoisolator transmitter. The receiving side of it is connected the I/O pin of the Arduino. You can see the schematic as well as a demo clip after the break.

This use of hardware frees up a lot of your microcontroller cycles. That’s because projects like this banana piano use the timers to measure RC decay. [Hasbi's] setup provides a digital signal that at most only needs to be debounced.

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Turning toy pianos into MIDI keyboards

Building a MIDI device is always a great microcontroller project, and nearly everyone has an old toy keyboard lying around in the back of a closet or in the basement. [JenShen] decided to take one of these toy keyboards and build a MIDI keyboard.

The keyboard [JenShen] used was a simple Casio keyboard with built-in voices. After tearing out the guts of the keyboard, the only thing that remained is the row of push buttons underneath the keys. These buttons were laid out in a row/column matrix, so [JenShen] needed to decode this matrix before sending the result to an Arduino for processing.

A 74HN595 shift register was used to read the 8 rows of buttons underneath the keys, while the rows were tied to different input pins on the ‘duino. This allowed [JenShen] to scan the keyboard matrix with an Arduino and generate MIDI notes and send them to other synths.

In the video after the break, you can check out [JenShen]‘s circuit and code that allowed him to turn a toy keyboard into a proper 32-note MIDI keyboard. It’s not velocity sensitive, but he says he’ll show everyone how to accomplish that in a future post.

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LED illuminated isomorphic keyboard looks as good as it sounds

Unlike the traditional ebony and ivory found on pianos, isomorphic keyboards arrange buttons on a grid. This makes every chord the same shape, and to transpose a piece it’s simply a matter of moving your fingers a few places to the left or right. [Brett Park] sent in an isomorphic keyboard he built loaded up with LEDs, and we’re thinking it the perfect instrument for musicians looking to move up from playing their MacBook.

The body of [Brett]‘s keyboard is made out of a sheet of acrylic. After drilling 64 holes for each of the clear arcade buttons, [Brett] bent the sides of his hexagonal keyboard into a very sturdy-looking enclosure.

On the hardware side, [Brett] used a 64 button Arduino shield and a Sparkfun MIDI shield. The RGB LEDs behind each button are controlled via MIDI sysex messages generated outside the instrument, making it perfect for a little bit of visual feedback from whatever soft synth you desire.

In the videos after the break, you can check out the light patterns in action along with one of [Brett]‘s improvs. Notice how all the chords are the same shape, and changing the key only requires [Brett] to move his hands slightly to the side.

[Read more...]

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