Add basic building instructions

README.md

@@ -1 +1,27 @@
 # Prusa-Firmware-MMU-Private
+
+## How to prepare build env and tools
+Use tools from the Buddy FW and a separate Atmel AVR GCC 5.4.
+
+Extract the AVR-GCC to some dir, e.g. `/home/user/AVRToolchainMMU/avr8-gnu-toolchain-5.4.0`
+
+```
+mkdir .dependencies
+cd .dependencies
+ln -s ../../STM32Toolchain/clang-format-9.0.0-noext
+ln -s ../../STM32Toolchain/cmake-3.15.5
+ln -s ../../STM32Toolchain/ninja-1.9.0
+ln -s ../../AVRToolchainMMU/avr8-gnu-toolchain-5.4.0
+```
+
+## How to build the preliminary project so far:
+Please make sure you have your `cmake`, `clang-format` and `ninja` in path
+
+```
+mkdir build
+cd build
+cmake .. -G Ninja -DCMAKE_TOOLCHAIN_FILE=../../cmake/AnyAvrGcc.cmake
+ninja
+```
+
+Should produce a firmware.hex file