PLEASE, TEST FIRST IF IT WILL WORK FOR YOU BY USING THE COMPANION GPS PROTOCOLS APP - https://play.google.com/store/apps/details?id=com.michalbures.garmin.protocols
IF THE APP CAN'T CONNECT TO YOUR GPS please check with USB Device Info app (https://play.google.com/store/apps/details?id=aws.apps.usbDeviceEnumerator) if your Android device can see the GPS connected. If yes, then please send contents of the app log (top right menu button) to email@example.com, so I can try to figure out what is the problem.
GPS External Signal allows you receive GPS location from your Garmin GPS in any app on your Android device.
One example where this can be useful is boats, where you can take a dedicated Garmin GPS with good reception and connect it to your table and there you can use the myriad of map apps. Another example are Garmins OEM sensors or other display-less GPS devices. With this app you can get the position data on your shiny and large tablet.
To find out if GPS External Signal is compatible with your devices please use the companion app GPS Protocols - https://play.google.com/store/apps/details?id=com.michalbures.garmin.protocols
You can also use USB Device Info app (https://play.google.com/store/apps/details?id=aws.apps.usbDeviceEnumerator) to check if your Android device can see the connected GPS.
For further information see http://bures.io/products/android/gps-external-signal/
In order to log received locations to gpx file
In order to provide received locations to Android