I see Quartus project, an RTL folder, an IP folder, Software and Tools.
Can somebody explain the contents of these folders, and the languages which the contents are coded in. It would be useful too if somebody can draw me towards the OSSC software implementations of the various low pass filters etc. The reason I ask if I am planning on studying and extending some of the OSSC capabilities.
Quartus only manages RTL (in Verilog) compilation. Nios2 toolchain (which comes as part of Quartus installation) is required for software (in C) compilation and debugging. Low-pass filters are not implemented in software or FPGA logic, but in the digitizer chip which is controllable via I2C.