connect garmin etrex to navico tp-300cx
 

Hello, I'm trying to connect a Garmin eTrex Vista Cx with Tillerpilot-300cx simrad. I'm using a USB-to-serial adapter and connecting pins 5 and 6 (nmea) and the tillerpilot not responding.
The output GPS signal on my laptop works well..
I'm not sure of the correct operative of the tillerpilot. According to the manual, it says just press the "Nav" key but doesn't work.
My final intention is to connect everything to a laptop, but as it does not work, I'm trying this first.
Thanks for your time!
Josefo.