garmin etrex 20 gps

[fiunary]

Hello, this issue has been touched on quite a bit, with indications that you can use a handheld GPS like the Garmin Etrex to give a GPS position to OPEN CPN on a Mac. I want to setup a backup system based on OPEN CPN and a Macbook Pro and the handheld offers a flexible option - can be used to help with paper chart navigation if the electrics go down.

Some forum members seem to say that you can and others that you need an NMEA compatible device and that the Garmin's USB won't do the job?

Many thanks.