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“Do I need a Garmin bridge for my device?” (Single ended vs. differential) RS232 VS RS422

Posted: Tue Jul 24, 2018 8:53 am
by admin
In the world of marine technology there are the NMEA standard protocols. These run from NMEA 0180 to the modern NMEA 2000. These protocols keep all the marine technology on your vessel talking to each other in the same way. However this can be a problem for a consumer who wants to upgrade his system but keep his older equipment.
If we say the system runs NMEA 0183 with a differential connection (rs422) (lots of marine products use this connection) and we want to connect to an older device running NMEA 0183 with a single ended (rs232) (Garmin devices like chart plotter 3000 series). Then we need a bridge to help transfer the information smoothly from one device to another so that they are compatible with each other.


Here at quark-elec our bridge device means you can still keep your new system and have your older hardware working on it. This cost effective solution we offer for currently £15* means that you don’t have to spend more money on very expensive equipment.
The Garmin Bridge is primarily designed for Garmin devices running the NMEA 0183 with a single ended output. It can be very hard to determine whether your Garmin device is using this single ended signal. The best way to find out what signal is being sent out is to read the manual carefully looking for references to NMEA or to call the manufacturer. We often see TX and RX for devices needing the Garmin bridge. This is the single output compared with the differential NMEA OUT-/A and NMEA OUT+/B.
Below is a table to help with the most common setups:-


Generally speaking Garmin devices especially chart plotters on or below the 3000 series are outputting in a single ended capacity. Newer devices like the Garmin 4000 typically use a differential output. The advice is to always ask before buying or to ring the manufacturer up to ask and check. Sometimes a bridge isn’t needed; we know of some companies and what can help when setting up devices. The table below can help:


We here at Quark-elec understand the difficulty of this problem and hope the bridge device will solve lots of our customer’s issues with crossover compatibility. If you have any queries or doubts about our bridge device, then consult our forum for more information or contact us directly and we will try and help.
*current price as of 3/7/18