Garmin 396 496 Data Connector Wiring Standard

I am in the process of wiring a Garmin 496 into my 182, using the
Garmin supplied accessory data cable. After reading about all of the
problems with the 396 496 Data Cable connectors coming apart, I cut the
cable to about a foot, installed a male DB9 connector on the cable, and
the matching DB9 female in the aircraft. This way, future replacement
becomes simple.

This enables you to discard most of the pis*-poor thermoplastic
insulated wires, which are way too small in terms of current carrying
capacity, anyway. This way, all of the wiring under the panel can be
done with proper Tefzel ms aircraft wire, which should make your
inspector happy.

The power leads can be properly sized (24awg), the audio can be
shielded, the RS232 data lines can be shielded, etc. This minimizes the
ground drop along the Garmin Data cable ground wire, so you may not
have to use a "ground-loop-isolator" to get rid of the whine in the
stereo feed, as a lot of folks have had to do.

Also, in the event of a Garmin connector failure, you can make a new
interface cable at home, starting with a new cable from Garmin and a
new DB9 male, without ever having to stick your head under the panel of
the airplane! You can even carry a spare, and change it "on the fly"
(pun intended).

I'm suggesting that this be adopted as a "standard", so all of us that
use Garmin 396/496 portables in our aircraft can be "interoperable".
Here is the wiring that I'm using and proposing:

__________________________________________________ ____

GARMIN 396/496 DATA INTERFACE CONNECTOR WIRING
(Using Garmin 010-10513-00 Power/data cable and
hooded Male DB-9 connector) MGM Oct 24, 2006

Pin#.Color..Description
------------------------------------------
1....Blk....DC input
2....Wht...Alarm (active low)
3....Brn....Voice+ (Bitch in the box)
4....Blu....Port 1 RS232 Out
5....Vio....Port 2 RS232 Out
6....Blk....Common ground
7....Org...Voice- (Bitch in the box)
8....Yel....Port 1 RS232 In
9....Grn....Port 2 RS232 In

Please disseminate this as widely as possible.

Mike Mladejovsky
__________________________________________________ ______

Fixing a typo: the DC input wire (Pin 1) is red!


mikem wrote:
I am in the process of wiring a Garmin 496 into my 182, using the
. . .
__________________________________________________ ____

GARMIN 396/496 DATA INTERFACE CONNECTOR WIRING
(Using Garmin 010-10513-00 Power/data cable and
hooded Male DB-9 connector) MGM Oct 24, 2006

Pin#.Color..Description
------------------------------------------
1....Red....DC input
2....Wht...Alarm (active low)
3....Brn....Voice+ (Bitch in the box)
4....Blu....Port 1 RS232 Out
5....Vio....Port 2 RS232 Out
6....Blk....Common ground
7....Org...Voice- (Bitch in the box)
8....Yel....Port 1 RS232 In
9....Grn....Port 2 RS232 In

Please disseminate this as widely as possible.

Mike Mladejovsky
__________________________________________________ ______

In rec.aviation.owning mikem wrote:
1....Blk....DC input
2....Wht...Alarm (active low)
3....Brn....Voice+ (Bitch in the box)
* 4....Blu....Port 1 RS232 Out
* 5....Vio....Port 2 RS232 Out
6....Blk....Common ground
7....Org...Voice- (Bitch in the box)
* 8....Yel....Port 1 RS232 In
9....Grn....Port 2 RS232 In

I think this is a good idea, but perhaps it should align with the DB9
serial port "standard" as introduced by IBM? This would mean putting
ground on 5 and port 1 RS232 connections on 2 and 3. The others could
go pretty much anywhere. The main goal is to avoid a short - a
situation where the DC power or ground could end up on a pin that the
other box thinks is ground or power, respectively. Connecting an RS232
input to ground or +14 V isn't a big deal; that would read as an
undetermined state or a 0 respectively. Connecting an RS232 output to
ground or +14 V might not be as good, but most RS232 drivers are robust
enough to handle this. Grounding a voice input shouldn't do anything
bad; grounding the voice output might do something bad, depending on the
output amplifier.

The idea here is that if something starts screwing up, you can use a
"normal" 9-pin serial cable to plug a laptop into the modified cable on
the portable GPS OR into the airplane and find out what's going on.
This may not be so important on the portable GPS side, as you could
always unplug the modified cable and use a standard cable from the GPS
manufacturer, but on the airplane it could be handy. Of course if
you're making serial cables anyway, you could make some up that would
adapt your pinout to a "standard" DB9 serial pinout.

Matt Roberds

I did the same thing and also didn't think to make it standard
232 pinage for DB-9. An even better idea.

Bill Hale


wrote:
In rec.aviation.owning mikem wrote:
1....Blk....DC input
2....Wht...Alarm (active low)
3....Brn....Voice+ (Bitch in the box)
* 4....Blu....Port 1 RS232 Out
* 5....Vio....Port 2 RS232 Out
6....Blk....Common ground
7....Org...Voice- (Bitch in the box)
* 8....Yel....Port 1 RS232 In
9....Grn....Port 2 RS232 In

I think this is a good idea, but perhaps it should align with the DB9
serial port "standard" as introduced by IBM? This would mean putting
ground on 5 and port 1 RS232 connections on 2 and 3. The others could
go pretty much anywhere. The main goal is to avoid a short - a
situation where the DC power or ground could end up on a pin that the
other box thinks is ground or power, respectively. Connecting an RS232
input to ground or +14 V isn't a big deal; that would read as an
undetermined state or a 0 respectively. Connecting an RS232 output to
ground or +14 V might not be as good, but most RS232 drivers are robust
enough to handle this. Grounding a voice input shouldn't do anything
bad; grounding the voice output might do something bad, depending on the
output amplifier.

The idea here is that if something starts screwing up, you can use a
"normal" 9-pin serial cable to plug a laptop into the modified cable on
the portable GPS OR into the airplane and find out what's going on.
This may not be so important on the portable GPS side, as you could
always unplug the modified cable and use a standard cable from the GPS
manufacturer, but on the airplane it could be handy. Of course if
you're making serial cables anyway, you could make some up that would
adapt your pinout to a "standard" DB9 serial pinout.

Matt Roberds