CH32-V003-based Stylophone

Features

• 20-tone keyboard and octave-shift button
• Easily customizable, digitally synthesized sound
• USB bootloader from rv003usb
• Easy and cheap to build
• Powered by cnlohr's ch32fun environment

Note: Current schematic has an amplifier that doesn't work well. Despite being usable, it is rather quiet and inefficient, so I highly recommend designing your own (either with two mosfets and a driver like TC428 or a 20kHz low-pass plus a linear audio amplifier (like MD8002).

First time use

To build the firmware, you should firstly follow the instructions at ch32fun wiki to install the toolchain. You will also need to install cmake (alternatively, you can try to somehow integrate the project into the make ecosystem of ch32fun).

Prebuilt binaries for the bootloader, bootloader configuration utility and minichlink are available in bin folder for convenience. You can build them from source, but you'll need to apply the patch in bin/rv003usb.patch to the rv003usb repository at commit 4674694672937776d9196526dcf2af6adc5523bc (feel free to use a newer version, but you'll have to transfer the changes manually). The patch contains hardware-specific configuration.

To flash and configure the bootloader, firstly connect the WCH-linkE to the stylophone. (Note for people who got their boards from LSTME: the programming header is located directly above the microcontroller. The pinout goes from left to right as follows: 3v3, GND, SWDIO) Then, run the following command: Linux:

./bin/minichlink -a -w bin/configurebootloader.bin flash -w bin/bootloader.bin bootloader -b

Windows:

.\bin\minichlink.exe -a -w bin\configurebootloader.bin flash -w bin\bootloader.bin bootloader -b

After this is done, unplug the stylophone and the programmer, then proceed to the next section.

Build and flash

To enter the programming mode, connect the stylus and press F (the ninth key including semitones) on the stylophone keyboard. While this is pressed, connect the stylophone to your computer with a USB cable (do not connect a WCH-LinkE). You should now see a new USB device (on Linux, you should see it with lsusb. On Windows, it'll appear in device manager).

To build and flash the project, use the following commands (both Windows and Linux):

mkdir build
cd build
cmake ..
cmake --build . --target flash

This builds the project and flashes it using the USB bootloader, then immediately starts running the uploaded code.