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[Low-level] Programming of NXT Robots

Pavel Petrovič Department of Applied Informatics, Faculty of Mathematics, Physics and Informatics ppetrovic@acm.org July 9 th 2008. [Low-level] Programming of NXT Robots. Welcome to world of LEGO. LEGO Geometry. Low-level Programming of NXT robots, July 9 th 2008 .

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[Low-level] Programming of NXT Robots

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  1. Pavel Petrovič Department of Applied Informatics, Faculty of Mathematics, Physics and Informatics ppetrovic@acm.org July 9th 2008 [Low-level] Programming of NXT Robots

  2. Welcome to world of LEGO LEGO Geometry Low-level Programming of NXT robots, July 9th 2008

  3. You can build everything... Low-level Programming of NXT robots, July 9th 2008

  4. Programmable LEGO Manually programmable module in 1990 Low-level Programming of NXT robots, July 9th 2008

  5. Programmable LEGO TECHNIC Control Center 1993 Low-level Programming of NXT robots, July 9th 2008

  6. Programmable LEGO Control Lab Building Set 1995 Low-level Programming of NXT robots, July 9th 2008

  7. Programmable LEGO Code Pilot: programmed by sweeping barcodes (1997)‏ Low-level Programming of NXT robots, July 9th 2008

  8. Programmable LEGO LEGO Mindstorms RCX (1998)‏ 8-bit microcontroller Hitachi H8/300, 32kb RAM AUTONOMOUS Excellent tool for teaching basics of robotics, embedded systems, etc. at all levels Low-level Programming of NXT robots, July 9th 2008

  9. Programming RCX Robotics Invention System – event based, icons, visual, educational RoboLab – educational, visual, flow-chart based NQC – C-like language translated to bytecodes Lejos – Java-like language BrickOS – GNU C/C++ compiler – produces fast binary code, full flexibility of C language Many others... Low-level Programming of NXT robots, July 9th 2008

  10. LEGO Mindstorms NXT (2006)‏ 32-bit ARM7 microcontroller AT91SAM7S256 256 KB Flash 64 KB RAM BlueTooth, USB, I2C, high speed IEC 61158 Type 4/EN 50 170 100 x 64 graphical LCD, better sensors, motors Programmable LEGO Low-level Programming of NXT robots, July 9th 2008

  11. Built-in rotation sensors NXT Motors Low-level Programming of NXT robots, July 9th 2008

  12. Much stronger NXT Motors Low-level Programming of NXT robots, July 9th 2008

  13. Light sensor NXT Sensors Low-level Programming of NXT robots, July 9th 2008

  14. Touch sensor NXT Sensors Low-level Programming of NXT robots, July 9th 2008

  15. Sound sensor NXT Sensors Low-level Programming of NXT robots, July 9th 2008

  16. Ultrasonic distance sensor NXT Sensors Low-level Programming of NXT robots, July 9th 2008

  17. NXT Non-standard sensors: HiTechnic.com • Compass, Accellerometer, Gyroscope, Color, IRSeeker, … Low-level Programming of NXT robots, July 9th 2008

  18. Master-slave: only master initiates communication Master can connect up to 3 slaves Optional acknowledgement, request reply Mailboxes #1-10 Sending: Master: NXTCommBTWrite(slave, mailbox)‏ Slave: NXTMessageWrite(mailbox)‏ Receiving: both sides NXTMessageRead()‏ Unreliable & Quite complex, but does not block NXT BlueTooth Protocol Silvian Toledo: http://www.tau.ac.il/~stoledo/lego/btperformance.html Low-level Programming of NXT robots, July 9th 2008

  19. Programming NXT Low-level Programming of NXT robots, July 9th 2008

  20. Programming NXT Low-level Programming of NXT robots, July 9th 2008

  21. Programming NXT Low-level Programming of NXT robots, July 9th 2008

  22. Standard Software NXT-G Low-level Programming of NXT robots, July 9th 2008

  23. LEGO Digital Designer ldd.lego.com Low-level Programming of NXT robots, July 9th 2008

  24. Not eXactly C (NXC) • Derivative of NQC for RCX by John Hansen • BricX IDE • Excellent tools and features • C-like language with good documentation • http://bricxcc.sourceforge.net/nbc/ • NXT Power Programming book Low-level Programming of NXT robots, July 9th 2008

  25. NXC example: line-following int s; task main()‏ { SetSensorType(S1, SENSOR_TYPE_LIGHT_ACTIVE); SetSensorMode(S1, SENSOR_MODE_PERCENT); ResetSensor(S1); while (1) { if (Sensor(S1) < 48) { OnFwd(OUT_A, 75); Float(OUT_C); } else { OnFwd(OUT_C, 75); Float(OUT_A); } } } Low-level Programming of NXT robots, July 9th 2008

  26. Java programming for NXT • iCommand – direct command mode • Lejos • Object oriented language • Preemptive threads • Arrays, including multi-dimensional • Recursion • Synchronization • Exceptions • Java types including float, long, and String • Most of the java.lang, java.util and java.io classes • A Well-documented Robotics API Low-level Programming of NXT robots, July 9th 2008

  27. NXT Logo • Combines the power of educational programming language Logo with robots • wiki.robotika.sk/index.php/Logo_for_NXT 1. Interactive Imagine Logo project 2. Loadable imagine library (nxt.imt) 3. Interpreter of Logo 4. Stand-alone Low-level Programming of NXT robots, July 9th 2008

  28. NXT Logo example: line-following to "follow [] [ setsensor 3 5 128 motor 0 "onrev 40 while ["true] [ while [ge? sensor 3 59] [] motor 0 "float 0 motor 2 "onrev 40 wait 50 while [lt? sensor 3 60] [] motor 2 "float 0 motor 0 "onrev 40 ] ] Low-level Programming of NXT robots, July 9th 2008

  29. Issues of the standard firmware • Limited multi-tasking • Complex motor model • Simplistic memory management • Not suitable for development of tools • Design your own firmware! • NXT GCC project http://nxtgcc.sourceforge.net/ • Approach: Take the standard firmware and modify it Low-level Programming of NXT robots, July 9th 2008

  30. Architecture of Standard Firmware • Scheduler + modules • Each module: • Init()‏ • Ctrl()‏ • Exit()‏ • Scheduler periodically calls Ctrl() on all the modules • Method1: design a new module • Method2: call your code from Ctrl() function of some module • Programming Concept: STATE MACHINE Low-level Programming of NXT robots, July 9th 2008

  31. Modifying standard firmware • cUiMenuCallFunction(Function,Parameter)is called when user presses button to trigger various functions, set a global flag: if ((Function == 8) && (Parameter == 248)) run_example = 1; • IncCmdCtrl(void), check the global flag: if (run_example) example(); • Implement the example() function as state machine • All standard functions available + direct C coding! Low-level Programming of NXT robots, July 9th 2008

  32. void example()‏ { static int example_state = 0; static ULONG x; if (example_state == 0) { cDebugString2("example", 0, 5); dOutputSetSpeed(1, MOTOR_RUN_STATE_RUNNING, 75, 1); x = dTimerRead(); example_state ++; } else if (example_state == 1) { if (dTimerRead() - x > 1000) example_state = 2; } else if (example_state == 2) { dOutputSetSpeed(0, MOTOR_RUN_STATE_IDLE, 0, 0); cDebugString2("done", 0, 5); example_state = 0; run_example = 0; } } Low-level Programming of NXT robots, July 9th 2008

  33. Sources of Information • LEGO Official documentation http://mindstorms.lego.com/Overview/NXTreme.aspx • NXT Firmware Open Source • Software Developer Kit (SDK) • Hardware Developer Kit (HDK) • Bluetooth Developer Kit (BDK) • HiTechnic.com • LUGNET.com Low-level Programming of NXT robots, July 9th 2008

  34. Workshop • Today & tomorrow afternoon • 7 NXT bricks available • Hands-on creative exercise • Build and program the robot in your favourite environment, preferably modify the firmware • Welcome & Thank you for the attention Low-level Programming of NXT robots, July 9th 2008

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