Introduction to Lab 2

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1 Introduction to Lab 2 Programming in RTOS using LEGO Mindstorms Martin Stigge <martin.stigge@it.uu.se> 9. November 2009 Martin Stigge <martin.stigge@it.uu.se> Lab 2: LEGO 9. November / 20

2 Lab 2: Programming in RTOS using LEGO Mindstorms Lab goals: Basic programming on an embedded device Using the API of an RTOS for current tasks Lab preparation: Form groups: 3 students each Possibly refresh your C knowledge Make sure your Windows login works! Lab will be done on Fri, and in rooms 1312D and 1313D Have a look at the lab homepage Lab report: C code to all 5 parts Answers to the questions To my mailbox, building 1, floor 4; Deadline: Mon, at 10:00 Further: Demonstrate a working vehicle, participate in car race on Return all hardware you get Martin Stigge <martin.stigge@it.uu.se> Lab 2: LEGO 9. November / 20

3 LEGO Mindstorms Programmable LEGO brick with sensors and motors Comes in two generations: RCX generation (1998) NXT generation (2006) We will use the RCX platform Martin Stigge Lab 2: LEGO 9. November / 20

4 LEGO Mindstorms: Components Package contents: RCX unit: LCD display, 5 digits 4 Buttons Sensor inputs 1, 2, 3 Motor outputs A, B, C Infrared (IR) port Can store 8 programs Two touch sensors One light sensor Two motors RCX Internals: Hitatchi H8/3292, 32k RAM, 16k ROM, 8/16-bit architecture, 16MHz clock Martin Stigge <martin.stigge@it.uu.se> Lab 2: LEGO 9. November / 20

5 RTOS: LegOS (BrickOS) We don t use the standard firmware Instead: LegOS (nowadays BrickOS ) (Soft) Real-time operating system Multitasking OS core Provides C/C++ development environment Support for threads, priorities, semaphores, event handling Comprehensive API for low-level I/O accesses Rest of this introduction: How to Upload the firmware Compile/upload programs Write programs/use LegOS API Martin Stigge <martin.stigge@it.uu.se> Lab 2: LEGO 9. November / 20

6 LegOS: Firmware Upload 1 Start Cygwin (see lab homepage) 2 Compile firmware uploader if necessary (see lab homepage) 3 Upload firmware: (i) Power up RCX unit (six AA batteries, On/Off button) (ii) Power up IR transceiver (one 9V block battery) (iii) Connect IR transceiver to COM port (iv) Run firmdl: Example Run: Firmware upload $ cd / legos $ util / firmdl -s boot / legos. srec Transferring " boot / legos. srec " to RCX % $ Martin Stigge <martin.stigge@it.uu.se> Lab 2: LEGO 9. November / 20

7 LegOS: Program Compile/Upload 1 Compile program using make 2 Upload program using util/dll RCX and IR transceiver need to be running (and idle) Example Run: Program compile/upload $ cd / legos / demo $ make... $ cd.. $ util / dll demo / helloworld.lx $ To compile own programs: Edit demo/makefile and add newprogram.lx to PROGRAMS= row Martin Stigge <martin.stigge@it.uu.se> Lab 2: LEGO 9. November / 20

8 Remark: Working At Home You can do all this at home (using Windows/Linux/Mac) Some hints at lab homepage Biggest issue: IR transceiver needs COM port (RS-232) Only few boxes with USB RS-232 port Martin Stigge Lab 2: LEGO 9. November / 20

9 Programming For LegOS Ordinary C programs Have a look at demo/ directory! Listing: helloworld.c 1 # include <conio.h> // cputs (), cls () 2 # include < unistd.h > // sleep () 3 4 int main ( int argc, char ** argv ) { 5 6 cputs (" hello "); 7 sleep (1) ; 8 cputs (" world "); 9 sleep (1) ; 10 cls (); return 0; 13 } Martin Stigge <martin.stigge@it.uu.se> Lab 2: LEGO 9. November / 20

h > // sleep () 3 4 int main ( int argc, char ** argv ) { 5 6 cputs (" hello "); 7 sleep (1) ; 8

10 Programming For LegOS Ordinary C programs Have a look at demo/ directory! Listing: helloworld.c 1 # include <conio.h> // cputs (), cls () 2 # include < unistd.h > // sleep () 3 4 int main ( int argc, char ** argv ) { 5 6 cputs (" hello "); 7 sleep (1) ; 8 cputs (" world "); 9 sleep (1) ; 10 cls (); return 0; 13 } Martin Stigge <martin.stigge@it.uu.se> Lab 2: LEGO 9. November / 20

11 LegOS API LegOS C programs can t use standard C library But API offers a lot, including Input/Output (on LCD) Reading sensors (light/touch) Controlling motors Time functions (delay) Random numbers Multithreading (forking, semaphores) Wakeup on events Will do a short walk-through now See LEGO Command Reference! (Include corresponding header files!) Martin Stigge <martin.stigge@it.uu.se> Lab 2: LEGO 9. November / 20

12 LegOS API: I/O Input via buttons Input via sensors (see next slide) Output via LCD: Strings, integers and sound Example: User Input/Output 1 // Input via buttons 2 if ( getchar () == KEY_ VIEW ) { // Blocking call! } 5 6 // Output 7 cls (); // Clears LCD 8 cputs (" Foo "); // String Output 9 lcd_int (42) ; // Integer Output dsound_ system ( DSOUND_ BEEP ); // Short " beep " Martin Stigge <martin.stigge@it.uu.se> Lab 2: LEGO 9. November / 20

13 LegOS API: Sensors Touch/light sensors on inputs 1, 2 and 3 Read values from boolean/integer variables TOUCH 1, TOUCH 2, TOUCH 3: Touch sensors (boolean) LIGHT 1, LIGHT 2, LIGHT 3: Light sensors (integer) Active/passive mode Example: Sensor input 1 # define DARK_ THRESHOLD ds_ active (& SENSOR_ 1 ); // Set 1 st sensor to active mode if ( LIGHT_1 < DARK_ THRESHOLD ) { 7 // Handle darkness 8 } Martin Stigge <martin.stigge@it.uu.se> Lab 2: LEGO 9. November / 20

14 LegOS API: Motors Motors can go forward/backward.. at a certain speed (between MIN SPEED and MAX SPEED) Can also brake (block movements) Example: Motor Control 1 // Motor A full speed forward 2 motor_a_dir ( fwd ); 3 motor_a_speed ( MAX_SPEED ); 4 5 // Everything full stop 6 motor_a_dir ( brake ); 7 motor_b_dir ( brake ); 8 motor_c_dir ( brake ); Martin Stigge <martin.stigge@it.uu.se> Lab 2: LEGO 9. November / 20

15 LegOS API: Time and Randomness Delay execution: sleep() (seconds) and msleep() (milliseconds) Busy waiting: delay() Generate random number: random() and srandom() (set seed) Example: Time and randomness 1 sleep (23) ; // Sleep for 23 seconds 2 3 long int x = sys_ time ; // Read current time in ms 4 x += 1234; // Set x to time point 1234 ms later sleep ( x - sys_ time ); // Wait until time point x 7 8 srandom ( sys_ time ); // Initialize random seed with systime 9 if ( random () % 42 == 23) { // Execute this with ( not too ) low probability 11 } Martin Stigge <martin.stigge@it.uu.se> Lab 2: LEGO 9. November / 20

16 LegOS API: Creating Threads Create new thread from a function: execi() pid_t execi(&process_func, int argc, char *argv[], priority_t priority, size_t stack_size); PROCESS FUNC is function for new thread Two arguments: int and char** Returns an int Pass arguments via global variables or argc/argv Priorities: Between PRIO LOWEST (1) and PRIO HIGHEST (20) Example: Creating Threads 1 // Define thread function 2 int foo ( int argc, char * argv []) {... } // Create thread ( starts running immediately!) 5 execi ( foo, 0, NULL, PRIO_NORMAL, DEFAULT_ STACK_ SIZE ); Martin Stigge <martin.stigge@it.uu.se> Lab 2: LEGO 9. November / 20

17 LegOS API: Events Suspend thread until wake-up event: wait event() wakeup_t wait_event(wakeup_t(*wakeup) (wakeup_t), wakeup_t data); wakeup is function for event check Argument and return type: wakeup t (i.e., integer) Is called by OS every 20ms, releases thread if non-zero return value Example: Event Waiting 1 // Define wake - up function 2 wakeup_t sensor_ press_ wakeup ( wakeup_t data ) { 3 return TOUCH_1 TOUCH_3 ; 4 } // Wait for event 7 wait_ event ( sensor_ press_ wakeup, NULL ); 8 // Sensor pressed! Note: sleep() is implemented like this. (Exercise: How?) Martin Stigge <martin.stigge@it.uu.se> Lab 2: LEGO 9. November / 20

18 LegOS API: Semaphores Used for signalling between threads, e.g., locking Type: sem t Init: sem init(sem t *sem, int pshared, unsigned int value) Blocking Wait: sem wait(sem t *sem) Non-blocking Wait: sem trywait(sem t *sem) Release: sem post(sem t *sem) See also: API reference Example: Locking Using A Semaphore 1 int A; 2 sem_t Asem ; 3 sem_ init (& Asem, 0, 1); // Semaphore gets initial value sem_ wait (& Asem ); // Aquire lock for A 6 A = 42; // Change A 7 sem_ post (& Asem ); // Release lock for A Martin Stigge <martin.stigge@it.uu.se> Lab 2: LEGO 9. November / 20

19 Lab Assignment Part 1: Simple Light Detector Attach only light sensor Write simple Geiger counter : More Light = Faster Beeping Nothing fancy, just to get a soft start Part 2: Static Cyclic Scheduling Build a car from LEGO bricks, with motors and collision detectors Write four tasks to control it and a cyclic scheduler for them Part 3: Adding a watchdog task Add a watchdog task to Part 2 Part 4: Multitasking in BrickOS Restructure program to use multiple threads (one for each task) Add light sensor and line tracking Part 5: LEGO Car Race Tune car so that it can follow a track as fast as possible Martin Stigge <martin.stigge@it.uu.se> Lab 2: LEGO 9. November / 20

20 LEGO Car Race Track looks roughly like this: Competition takes place on Fri, Fastest team wins! (Prize award included) Timeout is 5 minutes (if more: assignment failed, fix car) Keep in mind: Demo conditions might differ (different light etc.) Some hints: Build a physically robust car It should not break by itself! No hard-coding of light thresholds Calibrate at program start! Martin Stigge <martin.stigge@it.uu.se> Lab 2: LEGO 9. November / 20

21 The End Questions? (Now: Get LEGO boxes in groups of 3.) Martin Stigge Lab 2: LEGO 9. November / 20

Introduction to Lab 2

Introduction to Lab 2 Programming in RTOS on LEGO Mindstorms Martin Stigge 15. September 2010 Martin Stigge Lab 2: LEGO 15. September 2010 1 / 20 Lab 2: