New gadget testing

Along with load of keyer circuit board delivered today were some prototypes I had ordered.  I’m working on three different projects for the plane.

  1. Bluetooth stereo interface to the intercom.  This one is a little frustrating.  I have a BT stereo module, and the interface between the headset microphones and the mic input works fine.  I can make a call with my cell, and I sound fine on the other end.  However, the intercom music input is designed for speaker level outputs.  The BT module has line level outputs.  I have another one that will, like many others I see, drive speakers — but it has no mic input and the speaker drive is not suited for common ground.  I don’t want to add a separate stereo amplifier, but I may have to.
  2. The second board will allow switching between the Garmin GPS and a BT serial connection, so I can drive the autopilot from my tablet running Avare or Naviator.  This one needs a little tweaking but will be OK.  I had assumed since the BT serial module has a 3.3V output, that it is non-inverted serial.  Nope.  It’s inverted.  Tomorrow I’ll do some mods to turn the inverting level shifter in a non-inverting level shifter (it’s just a 2N7000 and a couple of resistors).
  3. Have not even assembled the third one yet, it’s a lower priority.  This one will let me add a canopy latch alarm to the Dynon D180 equipped RV-12.  I’ve gotten good about latching the canopy before the run-up, but I’d still like to get this board working.  It piggybacks the canopy latch on the spar pin line, and alarms if the spar pins don’t show as latched (kind of important), OR if the canopy is not fully latched AND the engine is above 3900 RPM.  That way you can start up and taxi with the canopy propped open, but it will alarm during the runup if it’s not latched.  To do that we have to monitor the serial data stream from the D180 to grab the engine RPM.