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iEFIS Lite external GPS and transponder setup issues

Posted: Fri Jan 21, 2022 1:33 am
by sparxfly
iEFIS Lite, TN72, TT21
TN72 connected to Lite RS232 port 2 RX (V16 on RS232 port 1)
TT21 via Trig interface on CAN bus
EFIS configured for GPS: External NMEA 9600 and Transponder: Mode-S on CAN bus.

The system is partially working, but some anomalies to sort out that I can't find in the documenation-
  1. The transponder is not transmitting the entered ICAO ID Octal code.
    The entered octal code is correct and confirmed retained through a power off/on cycle, but the code transmitted remains at some default setting.
    Software issue?
  2. The GPS position received by Airways is showing 'jumpbacks' of up to 500ft.
    In trying to identify the problem, the pop-up GPS status viewer does not show any activity when NMEA is selected, making me suspicious we are not receiving/using external GPS data.
    The serial port allocations for the Lite ports 1 and 2 do not list NMEA as an option- yet I am sure(?) I have seen that as a port 2 option on the Lite before?
    Makes me suspicious that the Lite will not accept external GPS withut an extender to provide Port 6 fixed NMEA, and is defaulting to the internal GPS source?