SL30 - EFIS - EMS - Comm Failure

[drill_and_buck]

I have my EMS D-120 connected to my EFIS D-100 via DSAB  buss and null modem serial cable and can share screens between units.

I have my SL30 connected to pin 22 on my D-100 and I can get the HSI display to appear per specs on my EFIS.

However as soon I connect the EMS D-120 to the EFIS D-100 via the null modem serial connection my SL30 Displays "COMM FAILURE"

I am not sure if the COMM FAILURE message is for the transciever uint or if the COMM FAILURE message refers to problems transmitting serial data to the EFIS.   Either way it is very disturbing to see.

My guess is that it sounds like there is a conflict on the serial EMS interface.

Anyone come across this problem?  

Thanks for any feedback.

Mike
RV-8

 

[drill_and_buck]

Re: SL30 - EFIS - EMS - Comm Failure - update

Last night I upgraded both units to the latest firmware release which allows you to configure the baud rate on the serial ports.

I tried every concievable combination of settins without any luck.

As soon as I bring the EMS online the SL30 will stop communicating with the EFIS unit.  The SL30 displays "COMM FAILURE" on the display and I then lose all the HSI data.

If I bring the EMS online, but disconnect the serial connection between the EMS and EFIS, things look good.   However, this prevents me from displaying EFIS data on my EMS.

Looks like the EMS is stepping on the SL30 serial communications.

Any ideas?

tks,

-Mike

 

[dynonsupport]

With a null modem connected, you have the EMS TX serial wire going to the EFIS RX serial line. Since the SL30 is also going into the EFIS RX line, its output is colliding with the SL30 and backfeeding into it. So it's both breaking the SL30 input, and the SL30 is throwing an error because of the data collision.

If you don't have a GPS hooked up to the EMS pin 19 serial input, move your SL30 over there.

If you do, you basically want to break the connection between pin 2 on the EMS serial connector (EMS serial TX) and pin 3 on the EFIS serial connector (EFIS serial RX). You can either build a new "null modem" type cable minus the above you - you'd need to run one wire between pin 2 on the EFIS 9 pin and pin 3 on the EMS 9 pin, and also, connect pin 5 straight across between the two 9 pins. Or, you could insert a switch in the EMS serial TX line to "break it" on the EMS side during normal use, but still allow you to reconnect it for firmware updates.

 

[drill_and_buck]

Thanks.

This makes sense.

You might want update the sections in the manuals for HSI connections that state...

IF YOU OWN AN EMS AND AN EFIS (NOT FLIGHTDEK-D180)

First, ensure that your EMS and EFIS are connected as described in EFIS and EMS
Intercommunication on page 3-4 and Dynon Smart Avionics Bus (DSAB) Wiring on 3-9.

Mike

 

[lgingell]

drill_and_buck,

I have seen this message before on an SL30. It appeared to be that that NAV part of the unit (from the bigger connector on the back) had powered up, but the DB15 (COM connector) wasn't fully seated, and the SL30 realised that that COM board in the SL30 wasn't powered and connected externally.

Anyway, I reseated the SL30 in its chassis, and it was fine.

I'm 99% sure that COM