[bobdec]

On my 2015 SX the power for homelink is the yellow/orange wire pin 1 the R11 connecter at the mirror. The power is from the smart junction box and remains on for a period after the ignition is turned off as to allow homelink operation after ign is turned off. . Pin 10 pink wire supplies power to the compass mirror and has power only when ignition is on. Back up signal is pin 9 and ground is pin 8. NOTE my 2015 SX may not match your EX wiring so use caution..

 

[bobdec]

This will give you an idea MirrorTap Power Cord . You have to make your own as they have a male and a female end, DIY with thin gauge solid coper wire, if you have any around.

When I installed my top mounted equipment I ran wires to the smart junction box and used a fuse tap for power. The left front piller cover comes off with one screw. I snaked wires between the top of windshield , down the pillar , then into the fuse box. Be carful the keep wires away from air bag in pillar. Since you are only needing power for homelink the mirror tap procedure may be easier. I would verify all voltages and grounds prior to doing anything as schematics for different models vary considerably.