An easy-to-use code flow diagramming tool?

Projects Programming
5

I'm talking Arduino Nano C-Code.

I am trying to get a USA public high school teacher and students involved with the code that drives my robotic 1/10 scale radio control car.

See:
Arduino based autonomous radio control model car
http://arduino.cc/forum/index.php/topic,84400.0.html

Reading the code would be much easier with a code flow diagram to reference. My computer does not have VISIO. Logicator seems too specific. I'll give Dia a shot....

Thanks, Ken