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Last night I left the hangar a little stumped. The GAD29 (ARINC Interface) was the only CAN bus device on the network, and it was not communicating with the Garmin G5. When I got to the hangar tonight I upgraded the G5 and still no communication. Next I buzzed out the CAN bus impedance and I had a AH-HA moment - 120 Ohms! It should be 60 Ohms!  There are two 120 Ohm resistors on either side of the CAN bus, so the fact I am only reading 120 Ohms means one side is not right, or I have a break somewhere. My termination resistor in the cabin is the Garmin G5, so I decided to pull the cable off of the resistor pack to see what the result would be - and it was zero change! Still 120 ohms! A quick look at the DB9 connector into the G5 showed something amazing - a pin that wasn't fully seated in the DB9 connector! I reseated it and BOOM! 60 ohm magic.  The GAD29 was HAPPY - the green light was flashing meaning CAN bus was UP!  The G5 agreed! CAN BUS IS HAPPY!  No error rate! Now I am happy!  The GAD29 was receiving what it thinks is valid ARINC data from the GAD29.  AFSC - this is new to me.  I wired up the GMU11 magnetometer and turned on the Autopilot servos. This CAN bus is ALIVE!  Going through the menus, I checked out the AP disconnect switch functionality. This is when the switch is not depressed.  When I press the switch, AP DISC goes LOW!  I was about to go home, but the only CAN bus device not on the network is the GMC507, and it's only 4 wires.  The GMC507 is powered by the same switch that powers the autopilots. When I turned it on, it came alive and lit up.  The G5 showed it active on the CAN bus and the Annunciator test switch turned on all of the LED's.  I am getting version information for the GMC507 but now the green checkmark of happiness. Something to look into...  The GMU11 magnetometer is not calibrated, so HDG is X'd.  And also I get this happy error message confirming the G5 X on HDG. What a GREAT NIGHT! So much done in so little time! Excited to get this all more tested and see what functionality this AP provides in flight conditions. I AM SEEING THE LIGHT AT THE END OF THE TUNNEL!!! 
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Last Modified: October 5, 2024 |