Example showing how to establish a global direction in a group of blinks

bigjosh · July 11, 2020, 3:19am

Not a terribly difficult problem, but there are some details. Probably the subtlest gotcha is making sure that you will not form a feedback loop on the transition where a center tile stops being the center because the button is lifted or it is moved.

When you start, all blinks show their local north face in blue. Pressing the button on any blinks makes that blink the “center” and causes all other connected blinks to align to its north and show that in green.

Should work with any size group with total propagation time of <250ms (configurable) and be robust to dynamic topology changes.

github.com

bigjosh/Move38-Arduino-Platform/blob/main/libraries/Examples05/TheNorthFace/TheNorthFace.ino

// Demo showing how to coordinate a global compass direction across a group of blinks. 

// Each blink normally shows its own north face (face #0) in blue
// Pressing the button on a blink makes it the "center" and all the other
// connected blinks will sync to its "north" and show that in green.

// Each tile (starting with the center) sends out the compass angle on each face,
// so the center blink would send angle 0 on its face 0. When a tile recieves a 
// compass angle from a parent, it uses it to compute which one of its own faces
// is pointing north, and then uses that to send a correct global angle to its children.
// For example, if a tiel recieves an angle 0 on a face, then it knows the opsite face is 
// pointing north (angle 0). 


void setup() {
  // Function intentionally left blank
}

const byte NO_PARENT_FACE = FACE_COUNT ;   // Signals that we do not currently have a parent

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BGA · July 11, 2020, 7:13pm

Funny enough, this is exactly the heuristic I used in the game I am working on (except I used datagrams for propagation instead of face values). But yes, this is very useful to be able to deal with faces in a consistent way across all connected blinks no matter what they actual physical orientation is.