Garmin G5 Serial Data Question

The G5 has one RS232 bi-directional interface with one receive pin and one transmit pin (RX1, TX1). Each of these can be configured under different formats. For example TX1 can be used to send pressure altitude to a transponder while RX1 can take data navigation input from a GPS.

I have this very configuration currently using an aera 660 to feed the G5. However, I just added a GNC 355 WAAS navigator to the panel to replace the aera. So the 355 will now talk to the G5 via the RS232 input channel. Now the GNC 355 manual has me set RX1 to "MapMx" instead of NEMA or the like. But that's where things get wonky. When I change the G5 RX1 input to MapMx it causes the TX1 output to gray out and no longer provide for altitude encoding out. On any other input mode other than MapMx the output pin can be used for altitude.

Is this a limitation of the MapMx data format? If so I guess I will have to buy a stand-alone altitude encoder, something unexpected and not described in the marketing.

Jim

In your situation I would just use 'Aviation In' from the 355 and continue to use the G5 as alt data, MAPMX has more data but mainly when talking to a PFD/MFD type display I believe, and yes when setting 232 ports certain ones, like MAPMX, will only allow both RX/TX set to the same setting.

MapMX - Receives flight plan and navigation data from a Garmin IFR GPS navigator, and optionally
outputs frequency tuning data and receives radio status data for on-screen radio display. The preferred
data source when interfacing with an external navigator, and is only available from Garmin units with a
WAAS GPS receiver. When MapMX data is received, the G3X display can show more accurate
information about the external navigator flight plan (e.g. DME, arcs, and holding patterns).

G5 Serial Port Settings

You can configure the RS232 input and output of the G5 to different settings, but they must match in baud rate. In this case, the encoder output, and MAPMX input do not match, so they cannot be selected at the same time. The Aviation Input from the navigator provides less detailed GPS information than MAPMX, and this impacts the ability of the GPS Navigator to aid the AHRS in the G5. You would want to enable the internal GPS receiver in the G5 and add a GA 26C antenna to the G5, if you use the Aviation output from the Navigator.

Thanks,

Justin