Puck.js, Raspberry pi camera

Thank you, this helps
working through the following example
https://www.espruino.com/BLE+Music+Control

setWatch(function(e){
 print(e.time - e.lasTime);
}, BTN, { edge:"falling",repeat:true,debounce:50});

the puck returns "NaN" on press button, the puck is on 2v04