!252-0286-00L
Project Oberon's primary goal...
>was to design and implement an entire system from scratch,
>and to structure it in such a way that it can be described, 
>explained, and understood as a whole.
>
- Niklaus Wirth & Juerg Gutknecht (1992), "Project Oberon", Addison Wesley

ETH Vorlesung Systembau / Lecture System Construction
>Case Study: Custom designed Single-Processor System
>Paul Reed (paulreed@paddedcell.com)
>
- [First Lecture: Custom-designed Single-Processor: the RISC Architecture]
- Second Lecture: Project Oberon on RISC
>
>Review
- building from scratch is achievable and beneficial
- efficiencies from configurable hardware: sw/hw co-design
- simple yet powerful, open and extendable 32-bit RISC architecture
- exercises: simple access to hardware features, existing or new
- familiarity with FPGA tools: Verilog source to bitstream on-board
- taking care to verify design: resources and timing

Motivation for Project Oberon
- existence proof for building from scratch
- "as simple as possible, not simpler" - Einstein
- strictly no "bells and whistles", just the essentials
- clear, extensible design documented in one book
- teaching principles, "rather than only knowledge and skills" - Wirth

Oberon System Features
- fast file system, module loader and garbage-collector
- high-level, type-safe language for applications and implementation
- graphical, tiled window interface
- "Module.Command [params]" execution from any visible text
- self-hosted, yet small and efficient (~200K including compiler)
- built (and documented!) during 1986-1988 by two people part-time
- ideal for resource-constrained systems; reliability; security

Oberon User Interface (demo)
- heavily mouse-oriented, three buttons with "interclicking"
- command (middle button), e.g. execute command Edit.Open
- select (right button), e.g. select parameter (^)
- point (left button), e.g. set caret
- vertical user and system tracks for viewer placement
- non-overlapping viewers, temporary overlays
- "tool" viewers for organising commands
- on-screen diagnostic "LEDs"

Oberon Core Structure
- [handout OberonCore.pdf]
- inner core: memory, files and module loader
- outer core: viewer and task management
- applications: compiler, graphics editor; networking

Oberon Inner Core
- Kernel.Mod: memory allocation and garbage collection, disk sectors
- FileDir.Mod: flat file directory and garbage collection
- Files.Mod: files as byte streams, "riders" for access
- Modules.Mod: (recursively) load object code, execute commands

Oberon Outer Core
- Input.Mod, Display.Mod: drivers for keyboard, mouse and screen
- Viewers.Mod: division of screen into "tracks" and "viewers"
- Fonts.Mod: font file and glyph management
- Texts.Mod: text file manipulation and scanning
- Oberon.Mod: task loop and command execution
- MenuViewers.Mod: viewers with title and menu of commands
- TextFrames.Mod: rendering and editing of text
- System.Mod, Edit.Mod: commands for viewers/system, text editing
- that's it! :)

Applications
- OR[SBGP].Mod: self-hosted Oberon compiler
- recursive-descent, single-pass direct code-generation in 2854 lines
- Graphics.Mod, GraphicFrames.Mod etc.: graphics editor
- Net.Mod, Print*.Mod: optional network and printing system
- (file xfer, mail, instant messaging, time synch, remote printing)
- uses SCC.Mod: twisted-pair network device driver (now 2.4GHz wireless)

Simple Application (Stars)
- [handout Stars.pdf: "MODULE Stars"]
- bounce stars around a menu viewer
- module body: create background task with handler
- Open: create viewer and install into display hierarchy
- Handle: interpret viewer messages
- Step1: broadcast "Step" message to advance viewer display
- Run and Stop: install and remove background task

"Project Oberon" on RISC
- revival of the original system described in the book
- RISC5 processor replaces defunct NS32032
- complete system on 1MB RAM Spartan-3 board+daughterboard (SD-Card)
- simple 2.4GHz Nordic SPI wireless module replaces twisted-pair network 
- new 2013 edition of the Project Oberon book
- all freely available online (projectoberon.com)
- now on compact custom-designed FPGA board

From RISC0 to RISC5
- optional floating-point (FAD/FSB/Flt/Floor, FML, FDV)
- external asynchronous static RAM interface
- enhanced fast SPI for SD-card/flash and network
- PS/2 keyboard & mouse
- 1024x768x1bpp video output via VGA connector
- extra features only ~250-350 more lines of Verilog
- (RISC0 is ~265 lines)

Oberon Memory Map and I/O
- [000000H - 0000FFH] 256 bytes system area incl. module table
- [000100H - 07FFFFH] 512K module block area and stack
- [080000H - 0E7EFFH] 425K heap
- [0E7F00H - 0FFEFFH]  96K video framebuffer
- [0FFFC0H - 0FFFFFH]   64 bytes memory-mapped I/O
- FFFFC0 (-64)  milliseconds (rd) / -- (wr)
- FFFFC4 (-60)   -- / "LEDs" (last line of on-screen diagnostics!)
- FFFFD0 (-48)  SPI data / SPI data (start)
- FFFFD4 (-44)  SPI status / SPI control
- FFFFD8 (-40)  PS2 mouse data, keyboard status / --
- FFFFDC (-36)  keyboard data / --
- FFFFE0/4 (-32/-28) general-purpose I/O data/ctrl

FPGA Board USB DFU "Load-and-go"
- uses standard USB Downloadable Firmware Upgrade (DFU) protocol 1.1
- USB device interface on FPGA board is Microchip PIC16LF1459
- (PICs are simple microcontrollers similar to Atmel AVR in Arduino)
- 8-bit data, 14-bit instruction set, ~40 instructions
- on-chip peripherals including UART, SPI etc, A/D, D/A, timers
- programmed using Wirth's PICL language, DFU handler is 325 lines
- receives bitfile from USB, reverses bits & sends directly into FPGA
- flash upload facility (e.g. to copy Oberon filesystem back to PC)
- RISC program (and/or other data) can be appended to bitfile
- captured by FPGA and written directly to SRAM before startup

Booting/Installing the Oberon System
- 0. bitfile either comes over USB via DFU, or is loaded from start of flash
- 1. FPGA loads appended inner core from DFU, or from fixed area of flash
- (ROM bootloader in Project Oberon no longer needed - simplifies CPU)
- 2. system starts at 000000H, e.g. with jump to inner core init
- 3. initialises Kernel, Files, Modules
- 4. loads Oberon and dependent modules and runs Oberon.Loop
- download INIT.DFU (once!) to initialise new Oberon filesystem
- (files required for booting plus applications - OVERWRITES EVERYTHING!)
- download RUN.DFU anytime to cold-start (reboot)
- reset/ABORT button jumps to 0 (warm-start) to interrupt a crashed task

RISC Tools and Emulators
- emulator straightforward: simplicity of instruction set and I/O
- Peter de Wachter's portable RISC emulator (see projectoberon.com)
- (RS232 emulation for file transfer in and out of virtual machine)
- cross-compiler straightforward: simplicity of language and compiler
- projectoberon.com resources built using scripts and cross-compiler
- upload FPGA board flash (dfu-util -U risc.img) for RISC emulator

Nordic nRF24L01+ 2.4GHz SPI Wireless Network Transceiver
- 1Mb/s wireless to replace low-cost 230kb/s twisted-pair wiring
- nRF24L01 replaces original serial comms controller (SCC)
- simple packet frame format with up to 32 bytes of payload
- straightforward SPI command interface, FIFOs for rx and tx packets
- optional hardware acknowledge and re-transmit of dropped frames
- exercise 2c & 2d: provide network traffic monitor and time updates

Exercise 2: Project Oberon on the FPGA Board

Exercise 2a: Tools and Workflow
- download INIT.DFU once to establish a clean new Oberon flash filesystem
- (WARNING! THIS OVERWRITES EVERYTHING ON THE BOARD FLASH)
- boot system with RUN.DFU
- (this cold-restarts the system and can be done any time)
- Edit.Open Stars.Mod, change interval (e.g. 50mS)
- select MODULE, ORP.Compile @/s and run: Stars.Open, Stars.Run
- (if error: mark source viewer [ctrl-z] and Edit.Locate selected pos)
- System.Free Stars~ to unload when finished or before new version
- when making changes SAVE YOUR WORK (Edit.Store) frequently!
- can block-upload entire FPGA board flash (dfu-util -U risc.img)

Exercise 2b: Develop a Screensaver
- Step 1: modify Blink.Mod to IMPORT Input, Display, Viewers
- look at Input definition to get mouse X, Y and button state
- new global INTEGERs lastX, lastY to detect mouse move in Tick()
- re-employ z to count up on "LEDs" if no movement (and test it)
- (note MUST run Blink.Stop before unloading module - why?)
- Step 2: when z gets to (say) 10, blank screen (ReplConst)
- (and when z is beyond 10, stop counting at some point!)
- if z is 10 or beyond and movement, restore screen - but how?
- Step 3: use an M: Viewers.ViewerMsg to suspend/restore all viewers

Exercise 2c: Develop a Wireless Network Traffic Monitor
- (requires nRF24L01 SPI module)
- Step 1: modify Blink.Mod to add the following consts and procedures:
- CONSTs spiData = -48; spiCtrl = -44; CHANNEL = 5;
- SPI(n: INTEGER) writes n to spiData and waits for spiCtrl bit0=1
- (hint: ... REPEAT UNTIL SYSTEM.BIT(spiCtrl, 0))
- BeginCmd(cmd: INTEGER) sets spiCtrl to 02H (select network) then SPI(cmd)
- EndCmd() sets spiCtrl to 00H; EnableRadio() sets spiCtrl to 08H
- WriteReg(reg, val: INTEGER) BeginCmd(20H + reg MOD 32); SPI(val); EndCmd
- Setup() writes reg 0=7FH, 1&4=0, 5=CHANNEL, 6=07H, EnableRadio
- Step 2: modify Tick() to add local INTEGERs status and carrier
- BeginCmd(9); get status; SPI(0); get carrier; EndCmd
- i.e. SYSTEM.GET(spiData, status); SPI(0); SYSTEM.GET(spiData, carrier)
- display carrier MOD 2 * 80H + status DIV 2 * 2 + z on "LEDs"
- in Run, and at end of Tick, call Setup to reset receiver for next tick

Exercise 2d: Develop a Network Time Client
- Step 1: add proc. WordMode() to set ctrl to 06H;
- in Setup() also write reg 7=70H, 11H=20H, and
- BeginCmd(0E2H); EndCmd; all before enabling radio
- Step 2: in Tick after displaying status but before Setup():
- if ODD(status DIV 40H) then BeginCmd 61H, set WordMode
- SPI(0), get spiData into new variable hdr;
- SPI(0), get spiData into new variable len;
- SPI(0), get spiData into new variable time; EndCmd
- Step 3: if hdr DIV 1000000H = 47H and len=4, then Oberon.SetClock(time)
- import Display and ReplConst(1, 900, 10, 100, 100, 2) when time updated
- (or ReplConst(1, 1013, 744, 4, 4, 2) is more subtle)
- Step 4: run and check time is updated with System.Date

[end of second lecture and exercise]

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