This week I focused the majority of my time on the integration of the Raspberry Pi and the Teensy microcontroller. This involved further development of the communication standard between the two devices. Initially, I tried to use the pretty midi python library to aid in the processing and transmission of the midi file. The processing itself included adjusting the timing of the notes played based on the speed the user wished to play the file at, and stripping the file of any unplayed instruments. However, after further inspection, we noticed that the library took too many liberties with the byte representation of the file making it difficult for the teensy to parse its data. So we decided to create our own format for sending the necessary data. We decided on this protocol:
Preamble: first 4 bytes of file, contains length of file including length bytes
Each entry represents a note and is 5 bytes:
First 4 bytes: start time of note in millis
Last byte: bits 0-3 are fret, 4-5 are string
Using these rules, the teensy will be able to parse the data with much less complexity. This method was implemented on the Raspberry Pi using Uart.
This progress on the Uart communication puts me on track for the schedule we decided. For the next week, I want to continue to work on the communication between the pi and the teensy. Now the teensy should send back information to the pi about the user input. In order to implement this, we will need to define another protocol over Uart to send packets of information containing the time the user played a strum and whether the note was correct or not. In the future the Pi will use this data to generate statistics of the user’s playing and display on the website.