The Lego Programming Assignment

1
The Lego Programming Assignment

• Programmable microcomputer (Hitatchi H8/3932)
• Sensors and actuators
• Battery driven
• IR-transceiver

2
LegOS

• Small OS to be downloaded on the RCX unit
• Runs on Linux and Windows 95/98/NT
• Source code is freely available
• Not a hard real-time operating system

• LegOS supports
• Preemptive multitasking
• Dynamic memory management
• POSIX semaphores
• LegOS gives access to
• LCD-display
• Buttons
• IR communication
• Motors
• Sensors

3
LegOS System Calls

• LCD-display (5 chars)
• void lcd_int (int i)
• void cputs (char s)
• Memory management
• free(void ptr)
• malloc(size_t size)
• strcmp(char s1, char s2)
• strlen(const char s1)
• LNP LegOS Networking Protocol
• lnp_integrity_send(data,length)
• lnp_integrity_set_handler(func)
• lnp_logical_range(int)

• Semaphores
• sem_wait()
• sem_post()
• RCX Button Input
• getchar()
• wakeup_t dkey_pressed()
• Sound
• void sound_system(SOUND)
• void dsound_play(const note_t )
• Motor control
• motor_a_dir(enum MotorDir)
• motor_b_speed(int speed)

4
LegOS System Calls

• Sensors
• TOUCH_1, TOUCH_2, TOUCH_3
• LIGHT_1, LIGHT_2, LIGHT_3
• ROTATION_1, ROTATION_2, ..
• void ds_activate (SENSOR)
• BATTERY
• Task Management
• int execi(PROCESS_NAME, int argc, char argv,
  priority_t prio, size_t
  stack_size)
• exit(int code)
• kill(int PID)
• yield()
• wakeup_t wait_event(wakeup_t(wakeup)(wakeup_t),
  wakeup_t data)

• Miscellaneous
• sleep(int sec)
• msleep(int msec)
• random()
• srandom(int seed)
• long int sys_time

5
Programming Example

• include ltconio.hgt
• include ltunistd.hgt
• int main(int argc, char argv)
• cputs("hello")
• sleep(1)
• cputs("world")
• sleep(1)
• cls(" ")
• return 0

6
Programming Example

• int main(int argc, char argv)
• ds_active(LIGHTSENS)
• locate_line()
• follow_line()
• return 0

static void locate_line() motor_a_speed(NORMAL
_SPEED) motor_c_speed(NORMAL_SPEED)
motor_a_dir(fwd) motor_c_dir(fwd)
wait_event(dark_found,DARK_THRESH)
static wakeup_t dark_found(wakeup_t data)
return LIGHT(LIGHTSENS)lt(unsigned short)data
7
Assignments

• Assignment 1, Light detector Make a Geiger
  counter for light
• Assignment 2, Static Cyclic Schedule Construct
  a vehicle. Run a single thread that calls
  procedures corresponding to tasks in your system.
  The procedures should be called at regular time
  intervals. Tasks are engine_control,
  forward_run, direction_change and
  obstacle_handling

8
Assignments

• Assignment 3, Watch dog Add a task to you
  static schedule that checks that no procedure are
  going over its time budget.
• Assignment 4, Multi-threading - Implement the
  tasks in your system as concurrent execution
  threads scheduled by LegOS. Add task
  border_handling

9
Assignments

• Assignment 5, Game playing Let the vehicles
  communicate using the LegOS Network Protocol.
• The vehicle should be able to play
• tag when a vehicle hits another vehicle, it
  gets a point and the the other vehicle must be
  idle for a while
• catch one vehicle has the tag. When it succeeds
  to hit another vehicle the tag will be
  transferred to this vehicle.

10
Notes

• Labs are scheduled in rooms 1312 and 1313 on
  Thursday. The rooms are booked both Thursday and
  Friday.
• Come by room 1221 on Wednesday 4/4 to get the
  Lego Mindstorms Kit and to sign receipt.
• Assignment deadline 16 May 2001