BrickOS (legOS)

1. BrickOS (legOS) Presentation by Jeff Bargmann

2. Quick Intro: What is it? • Full-out operating system for our Brick! • Allows for running compiled C/C++ on the RCX • As will discuss later: Cross-Compiled with GCC compiler for uploading to RCX • API/reference docs for 3 types of intended users: • C developers (me) • C++ developers (me) • Kernel architects (not me, but could be you!)

3. Quick History • First released in July 2000 • Renamed from ‘legOS’ to ‘BrickOS’ in July 2002, however many documents out there still refer to its previous name. • Last update: v0.9, January 2005

4. BrickOS: The Brick… Operating System • BrickOS: Not just an interpreter, a full Operating System for your RCX! • Programs that are uploaded run natively to the processor (Hitachi H8/3292) onboard the RCX. • BrickOS’s kernel manages the running programs (scheduling, etc) while the OS provides hardware interfacing, runtime environment, etc.

5. The BrickOS Kernel • Capable of managing threads • 32k of memory available, not 32 variables! • Can use doubles and floats • Can store up to 8 programs on the RCX • Can generate random numbers • OS still has control ; run button can be used to control/kill execution, On/Off button always works. • Remote-control compatible. • Installed with ‘firmdl3’ program: • firmdl3 --tty=USB ../boot/brickOS.srec

6. Cross Compilation • Cross Compiling a program means compiling it on one platform for use on another. • Build platform: where the compiling happens • Host platform: where the compiled program runs • Here, that means compiling on Windows / Linux / etc, to object-bytecode that is native for the RCX’s processor

7. Cross Compilation (2) • It’s tricky to setup • On Windows: • Download Cygwin, a Linux-like environment for Windows • In Cygwin, build (or just download) the Hitachi-H8 cross compiler • Install brickOS, then from within Cygwin perform scripted operation to build/config it.

8. Working with BrickOS…the easy way (Windows) Bricx Command Center(+ Cygwin)

9. Coding for BrickOS • Setup for use with C/C++ code. • No fancy tricks! Plain ‘ol C/C++. • (And everything that comes with it ; inheritance, virtual methods, new/delete, etc possible w/ C++) • API reference for utilizing the runtime available for either language. • Library is very robust (…for an RCX…), and even allows for such things as networking.

10. The Display Display functions: • #include <conio.h> //The necessary include • lcd_int( int x ); //Write int to screen • lcd_digit( int d ); //Display digit next to man • lcd_clear(); //Clears entire screen • cls(); //Clears digits from screen • cputs(char *string); //Shows 5-char string

11. Motor Controls, Overview • When working in C: • Basic functions available to control speed, direction. • State accessed via external variables maintained by the OS. • (#include <dmotor.h>) • When working in C++: • Motor() and MotorPair(left, right) classes available • Control single motor, or more complex operations on two. • C++ object-oriented interaction made possible. • (#include<Motor.h>, #include<MotorPair.h>)

12. Motor Controls, Sample

13. Motor Controls, Sample

14. Sensors: Push & Light • Accessed in C by defined macros, that refer to external variables maintained by the OS. • Push sensors • Boolean: 1=pushed, 0=not • TOUCH_1, TOUCH_2, TOUCH_3 • Light sensors • Scaled value between LIGHT_RAW_WHITE (0x5080) and LIGHT_RAW_BLACK (0xffc0). • LIGHT_1, LIGHT_2, LIGHT_3

15. Sensors, etc:Rotation and others • Rotation sensors • ds_active(&SENSOR_1); //required to activate sensor • ds_rotation_on(&SENSOR_1); //turns sensor 1 on • ds_rotation_off(&SENSOR_1); //turns sensor 1 off • ds_rotation_set(&SENSOR_1, pos); //sets sensor value to pos (an int) • Read with: ROTATION_1, ROTATION_2, ROTATION_3 (int) • Battery level • An int, read by the BATTERY macro. • Front buttons • Check for pressed boolean state with macro:PRESSED( dbutton(), BUTTON_VIEW ); //checks the ‘view’ button’s state

16. Sensors, Code

17. Sound • Some sound functions: • dsound_stop(); //stop current sound • dsound_playing(); //query: ‘is playing sound?’ • dsound_finished(); //returns non-zero when sound playback has finished • dsound_set_durration( int length ); //sets length in ms of a 16thnote • dsound_play( note_t *notes ); • Plays a song defined an array of pitches and lengths

18. Sound

19. Advanced BrickOS Features • Threading • Events • Synchronization • Networking

20. Threading • Thread created and executed by the call: tid_t thread = execi( int(int, char**) *funct, int argc, char ** argv, priority_t priority, size_t stack_size); • Example int WatchButton(int argc, char *argv[]); execi(&WatchButton, 0, NULL, 1, DEFAULT_STACK_SIZE); Starts function WatchButton as a thread, with no parameters passed, with the lowest priority (0-20 scale), and with the default stack size (512).

21. Threading • Thread Functions: • void exit( int ret_code ); //exits current thread • void kill( tid_t tid ); //terminates thread tid • void killall( priority_t p ); //kills all threads w/ priority < p • (apparently no built-in ‘join’ available, nor a universal workaround) • void yield( ); //yields control to other threads • int sleep( int sec ); //sleeps for sec seconds • int msleep( int msec ); //sleeps for msec milliseconds

22. Events: ‘wait for this…’ • Events are an integrated part of the BrickOS kernel’s scheduler. • Upon switching context from another it will check ‘should-wake’ status of waiting threads. • You give it a function and a parameter ; your thread resumes when the function returns non-zero. • wakeup_t wait_event (wakeup_t(wakeup_t) *wakeup_func,wakeup_t data); • (wakeup_t is typedef’d as a unsigned long)

23. Events Sample

24. Synchronization • Counting-semaphores are provided by OS; uses classical Dijkstra definition of semaphores. • Along with basic sem_waitand sem_post (signal) operations, sem_trywait, sem_timedwait, and sem_getvalue are also available. • Implemented using events. • First-checked-first-awoken applies in the case of a signal with multiple threads waiting.

25. LNP (LegOS Networking Protocol) • Allows for communication between robot and PC via IR connection • Requires additional tools: • LNPd: deamon that runs on PC • Liblnp: the library required to build applications for the PC to work with the deamon • Documentation on even BrickOS’s own site is…sparse. For a little better luck, try:http://www.cs.brown.edu/courses/cs148/brickOS/ref/lnp.html

26. LNP, Basics • The Process • Create buffer • Transmit buffer, to address or broadcast • Some Functions Broadcasting: • int lnp_logical_write(const void *buf, size_t len); • void lnp_logical_fflush(); To An Address: • int lnp_addressing_write(const void * data, unsigned char length, unsigned char dest_address_and_port, unsigned char src_reply_to_port); Incoming Traffic: • void lnp_addressing_set_handler ( unsigned char port, lnp_addressing_handler_t handler ); • Some sample code at: http://www.ee.adfa.edu.au/staff/hrp/teaching/LegoMindstorm/testlnp.c

27. LNP, Other uses • Using the ‘Message’ buttons on the remote

28. Finally,something else cool • Know C#? • http://www.dcl.hpi.uni-potsdam.de/research/lego.NET/

29. Logo.NET • Research project, a GCC Compiler for C# to compile for use on BrickOS • First release Oct ’04, v1.2 released April ’05, v1.3 “upcoming” • What it can do so far • Floats, doubles, string literals, all your basic types • Delegates • Arrays • Classes, including static/instance attributes, properties, and consts • Control flow operations • What’s not, yet • Strings (advanced), Multi-Deminsional Arrays, Interfaces, Exceptions, Most all pre-defined classes • Are they still working on it? • Maybe?

30. Logo.NET,Sample Program using System; using brickOS; namespace LineTracker { class LineTrackRunner { const short bright = 42; const short dark = 30; static void Main() { // Activate light sensor dsensor.ds_active(dsensor.SENSOR_2); // "3-2-1" Count down for (short i = 0; i < 3; i++) { dsound.dsound_system( dsound.DSOUND_BEEP); unistd.msleep(500); } Go(); //begin! } static void Go() { //Start the dmotor.motor_a_speed( dmotor.MAX_SPEED); dmotor.motor_c_speed( dmotor.MAX_SPEED); // Main loop while (true){ if (dsensor.LIGHT_2 > bright) { dmotor.motor_a_dir(dmotor.rev); dmotor.motor_c_dir(dmotor.fwd); } else if (dsensor.LIGHT_2 < dark) { dmotor.motor_a_dir(dmotor.fwd); dmotor.motor_c_dir(dmotor.rev); } else { dmotor.motor_a_dir(dmotor.fwd); dmotor.motor_c_dir(dmotor.fwd); } } }}

31. Conclusion • BrickOS is a great solution for comfortable C/C++ programmers, and fun for kernel or compiler writers. • Great for those looking to explore the wealth of power and raw ‘experiment-ability’ the RCX offers! • After the painful setup… • Quick development and testing • Stable and predictable • Comfortable language-environment • Powerful. Allows making full use out of the hardware

32. Oh, and… • Char: 1 byte • Int: 2 bytes • Short Int: 2 bytes • Long Int: 4 bytes • Float: 4 bytes • Double: 4 bytes • …and… • Despite best efforts, couldn’t get STL to work. Not much information out there. But maybe you’ll be the first!

33. References / Resources • BrickOS • http://brickos.sourceforge.net/ • BrickOS Windows Installation Guide • http://www2.acae.cuhk.edu.hk/~tliu/LegOS_install/legOS_install.htm • BrickOS Debian/GNU Linux Installation Guide • http://brickos.sourceforge.net/docs/install-Debian.html • logOS How-To • http://legos.sourceforge.net/HOWTO/ • Programming Lego Mindstorms using BrickOS • http://www.it.uu.se/edu/course/homepage/realtid/h05/ass2/

34. References / Resources(Continued) • Quick LNP Reference • http://www.cs.brown.edu/courses/cs148/brickOS/ref/lnp.html • Bricx Command Center (v1.3) • http://bricxcc.sourceforge.net/ • Cygwin: Linux-like environment for windows • http://www.cygwin.com