What FAA requirements exist for electronic ignition systems on piston engines?
The ignition requirements are pretty straight-forward:


  §23.1165   Engine ignition systems.  
  
  (a) Each battery ignition system must be supplemented by a generator
  that is automatically available as an alternate source of electrical
  energy to allow continued engine operation if any battery becomes
  depleted.
  
  (b) The capacity of batteries and generators must be large enough to
  meet the simultaneous demands of the engine ignition system and the
  greatest demands of any electrical system components that draw from
  the same source.
  
  (c) The design of the engine ignition system must account for—
  
  (1) The condition of an inoperative generator;
  
  (2) The condition of a completely depleted battery with the generator
  running at its normal operating speed; and
  
  (3) The condition of a completely depleted battery with the generator
  operating at idling speed, if there is only one battery.
  
  (d) There must be means to warn appropriate crewmembers if
  malfunctioning of any part of the electrical system is causing the
  continuous discharge of any battery used for engine ignition.
  
  (e) Each turbine engine ignition system must be independent of any
  electrical circuit that is not used for assisting, controlling, or
  analyzing the operation of that system.
  
  (f) In addition, for commuter category airplanes, each turbine engine
  ignition system must be an essential electrical load.