CS 452/652 Fall 2019 - Lecture 26

TC1 Demo Review

TC1 Components

• sensor tracking
  • independent of path finding, stopping, even calibration
• timed stop
  • simplest version only needs stop distances
• path finding
  • on-loop destination: just change to different loop
  • off-loop destination: need proper path finding
• idle time computation
• interactive user interface
• start/stop robustness

Idle Time Computation

• use Timer1 or 2 at 508 kHz for system timer tick
• use Timer3 at 508 kHz for free-running measurement timer

  idleTime = 0;
  t0 = timer_value();
  for (;;) { // kernel main loop
    t1 = timer_value();
    leave_kernel();
    t2 = timer_value();
    if (idle) idleTime += (t2 - t1);
    idlePercent = ((unsigned long long)idleTime * 100) / (t2 - t0);
    // reset: idleTime = 0; t0 = timer_value();
  }
  

Märklin Controller

• half-duplex communication: do not send commands when sensors report
• non-interleaving: do not send other commands between turnout-set and solenoid-off commands
• other problems? please produce simple/small busy-wait example program (for bounty)

Start/Stop Robustness

• being able to quit your program - and restart
  • without reload
  • without reboot
• good for demos, but also helps development
• initialize BSS
• initialize data
• keep constants for initialization
• always/periodically check for exit key

Path Finding

• Dijkstra algorithm recommended, but feel free to disagree!
• pre-compute some information, but not entire paths!
• Dijktra's previous hop tracing is low-overhead and can be done on-demand