I learned more about how the SR22’s avionics are wired and I’ll describe this after a request for all SR22 owners with the engine monitoring package:
Let me know who you are. I think there are four of us SR22/EMM-35 owners. I would like to know if your Sandel has a “WX” with a red line through it in the upper right corner of the Sandel.
Now for some information on the avionics:
The Stormscope emits its information on an RS-232 channel and receives commands via this same channel. The Stormscope has other interfaces, but the RS-232 port is the only one used in the SR22.
Before the addition of the EMM-35 (the box added for engine monitoring), the Stormscope was connected directly to the ICDS-2000, which both receives SS data and sends commands to the Stormscope over their RS-232 link. There aren’t any commands that have to be sent to do normal operations. The only commands I know of have to do with diagnostics. Putting the Stormscope into cell or strike mode or turning it off don’t really affect the SS, they just change what the ICDS (or Sandel) do with the data stream from the SS.
After the EMM-35 is installed, it sits between the ICDS-2000 and the SS. I.e., the EMM-35 has two RS-232 channels, one to talk to the SS and one to the ICDS-2000. The EMM-35 receives the SS data stream, adds all the engine monitoring data, and spits out the combined data stream to the ICDS-2000. One implication of this is that if you pull the engine monitoring CB, you’ll loose SS data. The EMM-35 will also take commands destined for the SS from the ICDS-2000 and forward them to the SS.
The Sandel takes the same SS (or SS+Engine) data that the ICDS-2000 takes. It does this by simply listening in, so to speak, to the data stream. I.e., it is a passive RS-232 receiver of data on this channel and has no way to send commands to the Stormscope. This is why the stormscope diagnostic command in the Sandel has no effect – the Sandel’s RS-232 channel with the SS is in just one direction: to the Sandel.
One theory that the Sandel support guy and I have is that the EMM-35’s output, to which the Sandel listens, confuses the Sandel and so the Sandel gives up and puts the red line through the “WX”. The Sandel guy said that if the EMM-35 adheres to the standard protocol and extends it in a compatible way to add the engine monitoring information to the SS data stream, all should be well. But since the EMM-35 was made by Arnav and it requires a simultaneous update the the ICDS-2000, we can guess that those two boxes are speaking to each other in a format that suits them, but not the Sandel.
More wiring information: the RS-232 signal that comes from the EMM-35, to the ICDS-2000, and then goes to the Sandel, goes through a standard stereo 1/4" jack that is mounted just above the pilot’s right theigh just before it gets to the Sandel. This jack allows one to plug in a laptop (or other) computer to the plane in order to update the Sandel’s database. I saw the avionics guy at Cirrus do this just before I got my plane. So when there is plug in this jack, the data stream from the SS/EMM-35/ICDS-2000 is disconnected from the Sandel. No big deal, who needs lightning info when you’re updating the Sandel database? But it means that there is a convenient places to watch the RS-232 channel with SS data going to the Sandel. I put a meter on it today and saw characteristic voltages of an active RS-232 line. Given how close this connector is physically to the Sandel, and that there is just one connector between it and the Sandel, my guess is that the Sandel is receiving the data stream. And since the Sandel has the “WX” with red line, my guess is that it doesn’t like what it sees.
What would help me a lot is to hear from the other SR22 owners who have the EMM-35 and to find out if any have stormscopes and if so, whether they have the same problem as I do.