Hello, this is just another update on our keyboard project. I feel we got a *LOT* done since the last time I posted. The project is now going very smoothly, and we feel we are meeting our schedule very well. I feel like we are around 80% done. Anyway, I wanted to share with you the following recording:
Okay, I guess that’s not my best recording yet, but after a few frustrating days of trying to get our ATSAM2195 Atmel synthesizer chip to work, we finally were able to produce sound output. This note was our first recording of the sound output off the chip.
Our final project circuitry actually fits on only one breadboard. We have a pic microcontroller, which has the task of reading all the key states, and generating NOTE ON and NOTE OFF commands to the synthesizer chip whenever a key changes value. The commands are then converted to MIDI messages, and sent to the ATSAM2195 synth chip.
Final project layout
In the image above, you can see our entire final project, minus the Arduino and LCD display, and minus the audio amplifier my lab partner built for this occasion. We decided to switch to parallel mode communication with the synthesizer chip, simply because we felt it was a bit easier to get going. Anyway, here is a quick and dirty c file we wrote for the PIC18LF4525, with which we were able to communicate with the synth chip:
Next we need to integrate all the code for the keyboard controller, so actual key events on the keyboard trigger MIDI commands.
What I spent most of my time on lately was creating drivers for the Crystalfontz CFA533-YYH-KL LCD screen, which is a 2-row 16-character LCD display with 6 navigation buttons. We’re having an Ardueno Duemilanove control the LCD through a RS-232 connection. The navigation menu allows configuration of various things such as instrument, master volume levels, reverb, and chorus. We uploaded a list of the 128 different instrument sounds incorporated on the synthesizer chip.
We also incorporated commands to save current settings into the Arduino’s EEPROM, and restore to default settings. The settings are coordinated with the keyboard controller via I²C connection.
Testbench for LCD display controller
The I²C communication ended up not being straight forward, since I had trouble getting the Wire.h Arduino library to trigger interrupts in the PIC controller when the Arduino is asking for a byte of data. I ended up writing my own Master I²C drivers, which pretty much bit-bang the SCL and SDA signals. Using my library, I was able to get the Arduino talking quite nicely with the PIC controller.
Our current code files for the LCD display and menu drivers are as follows:
- arduino_module.pde – Arduino project main file
- common.h – Shared constants between keyboard controller and LCD driver
- menu_items.h – List of items in the LCD menu
As of now, the LCD driver is mostly complete, besides some later proof-reading. Also, I can think of a few more features I would like to incorporate if I find the time such as transposition, and I want to change some things about how the menu is displayed.
Anyway, next time I post, the project might be completely done, perhaps just over the 3-day weekend. I have just one more week to work on this project, during which time I’ll be finishing the final project, preparing a 20-minute presentation on the project, writing one of Dr. Peckol’s typically long lab reports, and conducting a demo of our design.