This little box from PAS-Thru Products Inc of Florida is a very neat solution to the tangle that I see on many DIY boat installations – including mine try as I might to keep it clean and simple.
There are three pairs of clip in connectors and jumper between each pair on each of 14 rows.
This means that you can simply strip a wire and slip it into the spring connectors just like a HiFi speaker connection.
You can also connect any one input to up to 5 other devices.
Plus – its all neat and tidy inside the box!
On top of this simple box the people at PAS-Thru also provide a nice spreadsheet that you can download to document what connects to what…this spreadsheet is worth using on your installation in any case even of you dont use the PAS-Thru box.
After a recent correspondence via this blog, I thought it would be useful to publish the interface information for this connection.
The Philips MK8 has two cables both with shields BUT the shields will only be connected at one end – this is the clue. So at the MK8 end there is a D-SUB 9 pin connector – open it up and have a look at the wiring….it is wired as follows:
SIGNAL OUTBOUND FROM MK8
Pin 3 – Red – NMEA OUT (to a listener)
Pin 8 – Black – NMEA OUT (to a listener)
Shield – connected to MK8 shield
(DO NOT connect the shield at your Listener end)
SIGNAL INBOUND TO MK8
Pin 2 – Red – NMEA IN (from a Talker)
Pin 7 – Black – NMEA IN (from a Talker)
Shield – NOT connected to MK8 shield
(DO connect the shield at your Talker end)
AT THE MT-500 DSC/VHF END
Connect to Phillips Mk8
1 Brown – INPUT DC + <<<<———- signal from Pin3 RED wire on MK8
2 Red – INPUT DC – <<<<———- signal from Pin8 BLACK wire on MK8
Connect to PC – Serial cable
3 Orange NMEA OUTPUT +
4 Shield NMEA OUTPUT –
Connect to Flash programmer
5 Green – Clock
6 Blue – Reset
7 Grey – PDI
8 Purple – PDO
Now to the NMEA Protocol
If you have done any research you will have realised by now that the NMEA protocol is really a very poorly implemented “standard” . What you have discovered about the wiring carries on into the programming of the chips that send the data. This standard is the NMEA 0183 protocol – now replaced by NMEA 2000 – which is also badly implemented. Just in case you are asking why – it is because manufacturers have used this confusion to protect market share and make their equipment incompatible on purpose.
NMEA 0183 version 2.0 sentences for GPS all start with $GP and then a 3 letter acronym.
$GP*** Sentence Titles APA: Autopilot Sentence “A”
APB: Autopilot Sentence “B”
BOD: Bearing, Origin to Destination
BWC: Bearing and Distance to Waypoint, Great Circle
GGA: GPS Fix Data GLL: Geographic Position, Lat/Long GSA: GPS DOP and Active Satellites
GSV: GPS Satellites in view RMA: Recommend minimum Specific Loran-C Data
RMB: Recommend Minimum Navigation Information
RMC: Recommend Minimum Specific GPS/TRANSIT Data ROO: Waypoints in Active Route (not in standard)
RTE: Waypoints in Active Route or GOTO
VTG: Track Made Good and Ground Speed
WCV: Waypoint Closure Velocity
WPL: Waypoint Location
XTE: Cross-Track Error, Measured
ZTG: UTC & Time to Destination Waypoint
So you can see that when the MT-500 DSC manual says $GPRMC / GGA they mean that the two sentences above must be being sent by the Phillips MK8.
The Phillips MK8 does comply with NMEA 0183 version 2.0 (January 1992 standard)
It will transmit RMC (Time, date, position, course, and speed data) every 2 seconds.
BUT it will also transmit GGA – Global Positioning System Fix data (Time, position, fix) if you have the MK8 with differential software. This was issued as a software upgrade after the MK8 started shipping.
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