Working on a new concept. Was inspired by a Eurorack design that I saw online… Basically, the original idea was a modular MIDI synth. It grew a little, but that’s still the basic concept.
It starts with the case, constructed from sheet metal and 8th inch plywood, 18”x8”x3”, with a 5” trough (I know it’s not Eurorack standard: I did say inspired by, not a copy). Modules are 6 inches tall. Power supply is a 12v wall wart, splitting off to +12v, -12, +5, +3.3, and ground. Completing the 10 conductor bus will be 4 pins carrying 2 UARTs at TTL level, that it will pick up from the Core Module.
Power supply connects to the Core Module, a limited MBNG box with SCS and built over 3 “blades” using a so called “black pill”. Anything I needed I included, which honestly wasn’t much.
Advantages of the uC include: low cost (about half the cost of a DISC board or even less), same chip as the Discovery, exposing just enough pins for it to do what I want it to, and more. Disadvantages: MIOS32 cannot use SDIO, I could not find a way to disconnect VBUS from the USB (figured out a workaround, see below), fewer pins than the discovery I guess, you have to use a cheap ST Link to program it… otherwise, it’s fine.
Stuff I’m using:
UARTs: we have Four native to the Core: the first two UARTs are external 5 pin, the other 2 are internal to the case. Additional UARTs are through iic MIDI boards: TK’s solution works fine I’m sure, but I decided to use Arduino clones of various make and model, mainly because I have these boards laying around, and why not?
USB MIDI: I did mention the workaround for the USB thing? I decided to ignore the built in USB port on the black pill, and I programmed an Arduino Pro Micro to act as the new USB MIDI bridge. Works just like the iic MIDI modules, but for USB.
Iic: running two IIC ports; First is for an IIC LCD, 4x20. The other is basically an IIC daisy chain for IIC MIDI modules and other IIC devices. Instead of the jumpers on the IIC MIdi modules, I’m using 4 position DIP switches for the iic address system, giving 16 different addresses.
SPI: SD card.
The circuit boards for the modules will be mounted vertically and broken up into interconnected “blades”, which will be mounted on L brackets directly to the steel of the module faceplate. The modules then slide into the case and are mounted to the steel of the case using m3 screws. Modules that generate sound or that otherwise transmit or receive Data are fitted with 4 position DIP switches for MIDI channel selection.
First planned modules will be the Statler Pressure cooker ( an ESP32 based clone of the Waldorf Microwave), two RP2040 based step sequencer, a drum module, and a mixer. Analog synths and such are on the table for later.