In the words of Shakespeare, "if music be the food of love, play on."
For our final project, we will be recreating a harmonica using the FRDM-KL46Z board. Similar to a physical
harmonica, musical notes can be played through continuous movement and pressure. However, unlike the
harmonica where you use your mouth and breath to play the notes, the digital harmonica is played on the
FRDM-KL46Z board by sliding one's finger over the capacitive touch sensor. The respective notes can then be
viewed through the terminal of your device and heard through the connected device’s speaker system. The
motivation for this project stems from the cultural relevance of creating music. It can become the
inspiration to creative inventions by providing another means of access to young enjoyers of music all
around. Furthermore, the project gave us the opportunity to really explore the course materials and experience
that we've gained this semester with its various labs and deliverables. Applying this understanding to a similar
environment/setup, we were able to be creative with its possibilities and make a project that connected to our own
musical interests.
Our project demo video is shown below to explain the project's design and usage. Created with Vimeo video editing software,
please enjoy our group's narration of the project design process and implementation!
Our first step of action was to work on the touch capacitor slider (TSI) and ensure that the
placement of the user's finger will give a correspondence to the note we hope to play. The TSI was configured using various
resources from the board's software support as well as external open-source projects oneline. To examine and fine-tune the accuracy of
this step, we first display the note on the liquid crystal display (LCD). The necessary set-up and configuration
for this implementation was done with provided course resources and further edited for our specific setup. Once we were sure that the
correspondence to the touch capacitor is in working as expected, we continue on working with playing the audio
corresponding to the note inputs. We accomplish this by making use of the serial port and the UART functions.
This configuration was also complex to implement, as the board's serial data had to be connected and communicating between
the two platforms - MCUXpresso and the Python script. However, we were able to link the two through the board's serial
identity and provide a one-way communication channel for the slider's data to be sent over and processed for sound output
via the Python terminal. Furthermore, we could expand on the sound settings and options while in the Python environment
due to the external sound libraries available on its platform.
Such that given the input of the touch capacitor from the FRDM-KL46Z board, we will be able to transmit the
data to our Python implementation and make use of it to play the audio provided the PyGame library. To ensure
the data is being transmitted between both implementations, we print the data we received in the terminal of
our Python implementation. Once we observe that the note inputs are received correctly, we are assured that
our system is in working condition with accurate positional data.
When all of the above testing is complete, we further refined the final system by
better developing the intervals of the touch capacitor such that there will be a more accurate one to one
correspondence to that of a physical harmonica. We also switched the LCD to a virtual terminal setup due to sensor
conflicts - the serial port and LCD pins are connected, so it was simple enough to modify our output display values.
However, this ended up giving us additional control over what was displayed due to the increased scope of the virtual terminal-
not only does it have more space for displaying messages (which is beneficial for debugging), but it's also more dynamic with
testing and implementing various output. Finalizing the testing for each of the aforementioned sensors and systems, we could continue
adding in additional capabilities eg. different sounds and usages. With a robust testing platform through the two displays and physical
controls, it was simple to add in various sounds and abilities. The benefits of a robust platform mean that continued iteration and
design are possible ie. adding in LED output or additional sensors. While we didn't implement these due to timing constraints, having
a stable set-up meant that we could easily build on our existing platform if wanted.
Work Distribution
We were able to collaborate by working together on different aspects of the
project and meeting later to elaborate on our progress.
The project started off with Sophia working on the touch capacitor and ensuring
that there is a correspondence between the touch capacitor and the note we would like to play. In this step of
our project, we proved the accuracy of the implementation by using the liquid crystal display (LCD). Such that
we were hoping that the LCD can then be used in our final system to display the note input. The next step was
then followed by Jia Ying who worked on the audio given the touch capacitor input. To transmit the data
between implementations, the serial port and the UART functions were used. Once the data can be received, The
PyGame library is then used to play the sounds we want corresponding to each individual note. It was at around
this point we realized there was a pin conflict between the UART functions and the LCD functions. We find
going around this will be challenging and given that the Python terminal can also display the notes, we
abandoned the idea of using the LCD. Instead we made better use of our time to work on refining our
implementation to ensure our system was accurate.
Whenever one partner had a pressing concern, the other partner was quick to
respond with possible solutions. Our expectations of each other were very clearly outlined throughout our
collaboration of the project and each step was facilitated readily.
