Cumae is a tiny software layer in plain C that is meant to act as a realtime OS for AVR-based devices.
SBuCa (Smart Business Card) is powered by Cumae; SBuCa makes use of a G2 controller that drives a 1.44" EPD display. As you may expect the whole thing is based around an AVR.
Cumae is a self-contained project that includes the whole gcc-avr toolchain, along with avr-libc and avrdude.
The usual one-liner for Ubuntu 16.04 is the following
sudo apt install build-essentials git texinfo flex bison libgmp-dev libmpfr-dev libmpc-dev libusb-dev libusb-1.0-0-dev libelf-dev libftdi-dev libftdi1-dev
The first thing is to clone this repository; do that by cloning the repository with git clone https://github.com/michelangelo/Cumae.git --recursive.
If you have already cloned the repository without appending the --recursive parameter, you can update all the submodules by running:
git submodule init
Followed by
git submodule update
Now that you have all the submodules nice and ready, you can build them all with:
tools/build/build-toolchain.sh
This is gonna take a while but if everything goes well you'll have all the tools in the out/ directory.
To build the main Cumae app just cd src/main and run make. Everything should build smoothly.
Pay attention to the file Makefile.in in the root of the repository for all the information about the target MCU and clock settings. The project default is for an atmega328p with a clock of 12MHz driven by a full swing crystal. An Atmel ICE is used as flasher (SPI).
Anyway, in order to flash your MCU you'll just need to issue make flash from the directory src/main.
You can add your own app on top of Cumae by simply creating a new sub-directory under src/. A Makefile needs to be present in every directory; by doing so you'll be reusing all the rules Cumae provides, such as the one to flash your MCU. Your Makefile only needs to define one target. Check the example in src/blink.