ossc/README.md

Open Source Scan Converter
==============

Open Source Scan Converter is a low-latency video digitizer and scan conversion board designed mainly for connecting retro video game consoles and home computers into modern displays. Please check the [wikipage](http://junkerhq.net/xrgb/index.php?title=OSSC) for more detailed description and latest features.

Requirements for building and debugging firmware
---------------------------------------------------
* Hardware
  * OSSC board
  * USB Blaster compatible JTAG debugger, e.g. Terasic Blaster (for FW installation and debugging)
  * micro SD/SDHC card (for FW update via SD card)

* Software
  * [Altera Quartus II + Cyclone IV support](http://dl.altera.com/?edition=lite) (v 16.1 or higher - free Lite Edition suffices)
  * GCC (or another C compiler) for host architecture (for building a SD card image)
  * Make
  * [iconv](https://en.wikipedia.org/wiki/Iconv) (for building with JP lang menu)


Architecture
------------------------------
* [Reference board schematics](https://www.niksula.hut.fi/~mhiienka/ossc/diy-v1.5/ossc_v1.5-diy_schematic.pdf)
* [Reference PCB project](https://github.com/marqs85/ossc_pcb)


Building software image
--------------------------
1. Enter BSP directory:
~~~~
cd software/sys_controller_bsp
~~~~
2. (Optionally) edit BSP settings:
~~~~
nios2-bsp-editor
~~~~
3. Generate BSP:
~~~~
nios2-bsp-generate-files --bsp-dir . --settings settings.bsp
~~~~
NOTE: the previous step must be done every time after RTL/bitstream is built
4. Enter software root directory:
~~~~
cd software/sys_controller
~~~~
5. Build SW image for target configuration:
~~~~
make <OPTIONS> mem_init_generate
~~~~
where OPTIONS may include following definitions:
* OSDLANG=JP (Japanese language menu. Run "iconv -f UTF-8 -t SHIFT-JIS ossc/menu.c ossc/menu_sjis.c" before make)
* DIY_AUDIO=y (Includes code for DIY audio board)
6. Optionally test updated SW by programming Nios2 CPU via JTAG (RTL-SW interface in active FW must be compatible new SW BSP configuration)
~~~~
nios2-download -g --accept-bad-sysid sys_controller.elf
~~~~


Building RTL / bitstream
--------------------------
1. Load the project (ossc.qpf) in Quartus
2. Generate the FPGA bitstream (Processing -> Start Compilation). NOTE: make sure software image (software/sys_controller/mem_init/sys_onchip_memory2_0.hex) is up to date before generating bitstream.
3. Ensure that there are no severe timing violations by looking into Timing Analyzer report

If only software image is updated, bitstream can be quickly rebuilt by running "Processing->Update Memory Initialization File" and "Processing->Start->Start Assembler" in Quartus.

Installing the firmware via JTAG
--------------------------
The bitstream can be either directly programmed into FPGA (volatile method, suitable for quick testing), or into serial flash chip where it is automatically loaded every time FPGA is subsequently powered on (nonvolatile method, suitable for long-term use).

To program FPGA, open Programmer in Quartus, select your USB Blaster device, add configuration file (output_files/ossc.sof) and press Start

To program flash, FPGA configuration file must be first converted into JTAG indirect Configuration file (.jic). Open conversion tool ("File->Convert Programming Files") in Quartus, click "Open Conversion Setup Data", select "ossc.cof" and press Generate. Then open Programmer, add generated file (output_files/ossc.jic) and press Start after which flash is programmed. Installed/updated firmware is activated after power-cycling the board.


Debugging
--------------------------
1. Rebuild the software in debug mode:
~~~~
make clean && make APP_CFLAGS_DEFINED_SYMBOLS="-DDEBUG"
~~~~
NOTE: Fw update functionality via SD card is disabled in debug build due to code space limitations
2. Program Nios2 CPU via JTAG and open terminal for UART
~~~~
nios2-download -g --accept-bad-sysid sys_controller.elf && nios2-terminal
~~~~
Remember to close nios2-terminal after debug session, otherwise any JTAG transactions will hang/fail.