Hi - I was talking to somebody yesterday and they mentioned that they use a really old communication protocol that I think had something like "1335" in the name. I remember him mentioning that it was very power hungry (I think .5-1W/node) and it was on a ring bus. I think he also mentioned it uses a transformer or something like that.
Anybody know what protocol/bus this is? Thanks!
-Mike
Probably MIL-STD-1553, used primarily in aircraft.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
That's it! Do you know, does it have any benefits over some more modern communication protocols, such as CAN? I'm interested mostly in regards to the two protocols operating in very, very noisy environments and which could handle such environments better.
Thanks!
-Mike
Though I've designed maybe a half dozen chips to MIL-STD-1553, I've never used it. But it _is_ a large differential signal... even modern perversions do ±3V... I believe the original flavor was ±10V.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
It is redundant, so is pretty reliable. But it's very old, slow, and fairly primitive, and a more modern protocol could be a lot better. But it's an aircraft standard, and it works.
John
Afaik, it is a transformer coupled dual redundant bus, using double screened twisted pair wire. The voltage at the transmitting end is around 30V, and when received (after going through transformers and series resistors is around 9V. Each bus has a controller which decides who sends what and when. There can be 30 Remote Terminals, each allocated 32 messages of up to 32
16-bit words. Each bit takes 1uS to send, using a Manchester encoded self-clocking waveform. There are four extra clock periods added to each word (start, stop...) so a word takes 20uS. Added to that is the command word time (20uS) plus the post-command response time (up to 10us). So overall it's a very reliable, predictable, noise-immune system that still works if the wire breaks (the controller automatically goes over to the other pair). hth NeilOn Wed, 20 Sep 2006 19:59:50 GMT, "neil" wrote: ...
and it has guaranteed response time, unlike Ethernet CSMA/CD
Is there anything in CAN that would make it unsuitable for small aircraft?
Gerhard
Depends on the electrical noise level. What is the voltage swing in CAN?
I did a chip design for a _very_ high voltage, low impedance signaling bus for the AH-64 Apache helicopter gunship. The problem was _extreme_ electrical noise from the solenoids operating the "Gatling" guns.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Hello Jim,
All this needs to be certified and that takes lots of money and time. If it isn't type certified you usually can't use it, no matter how good. Probably that's why so much old stuff is found in aeronautics.
Regular logic levels. This shows the ranges for unipolar and differential modes, scroll down to "CAN bus interface ICs":
Couldn't they modulate up to a band where the solenoid noise wasn't so loud? That's how we sometimes get around such pollution in medical electronics without resorting to extreme power levels.
-- Regards, Joerg http://www.analogconsultants.com
me:
probably less than 5V, differential. I'll look it up. one source:
at least it avoids CSMA/CD and is good enough for cars.
I was thinking more at planes like C172, C182 or gliders, no Apaches or A380.
Was there a reason not to go optical?
Gerhard
I don't know. I just design to the spec I'm told. I'm just a dooby ;-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
I wasn't the system guy. I'm only the circuit designer dooby ;-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Hello Jim,
In mil they have to segregate tasks and only pass info on a need-to-know basis, for good reason. That's different in medical. You sign an NDA and then all the wraps come off.
The best outcome for a client was when they more or less accidentally called me into a meeting about a system I wasn't tasked to work on. It resulted in ditching all fiber optics, the bulky batteries of an isolated module and >$1k per system in cost reduction. It won me a nice add-on contract but the sales rep for the fiber optics was very miffed.
-- Regards, Joerg http://www.analogconsultants.com
Hello Gerhard,
The 172 and 182 will need type cert. Don't know about gliders but noise fixing such systems in a composite structure is no small feat. I had to do that on a pusher design once. Almost gave me a back pain crawling around in there.
The main concern is avoiding data bus signals to leak into the VHF radio and nav gear. VHF is still the old AM there.
-- Regards, Joerg http://www.analogconsultants.com
There is no way around type certification, that's understood. But someone once said to me: with a system like CSMA/CD you don't even need need to start because there is no guaranteed response time in principle. As if the universe would last long enough to see 5 stations with 10% combined network load to fail a 1 sec. delivery time.
like cooling the cylinder heads with excessively fat mix or feeding the altitude encoder to the transponder with a wire per bit...
You are well known for your cost consciousness, but that hurts even me..
or the effort it took to pave the way for newfangled things like BPSK in mode S transponder uplinks.
regards, Gerhard
Hello Gerhard,
That depends on what's connected. Some things in aircraft need to run almost synchronously. But not all, of course.
Then there are good old aircraft that need no stinkin' bus, like this one at our airport:
What you can't see in the photo is that in our community you can taxi right from the garage onto the runway. Before we were allowed to buy our house we had to learn and sign off on regulations concerning the common usage of roads by automobiles and aircraft. I thought that was a joke. Until I saw that big DC-3 lumbering up the road.
Well, the heavier a sector is regulated the longer it takes for new things to take hold.
Our local airport is pretty much in non-compliance for night flights. The upgrade project is "going" more than five years now and none of the mandated hilltop lights have been installed where we live. Things can move very sloooowly when it comes to aeronautics.
-- Regards, Joerg http://www.analogconsultants.com
[snip] [snip]
We have communities here in AZ like that, Carefree and Chandler to name a few.
Hugh Downs, the old TV host, has such a place in Carefree.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
If you want to work on a military aircraft you may need it.
Unless it's fallen to the budget ax you could download all the military specs -- I'd just do a web search on "MIL-STD-1553".
-- Tim Wescott Wescott Design Services http://www.wescottdesign.com Posting from Google? See http://cfaj.freeshell.org/google/ "Applied Control Theory for Embedded Systems" came out in April. See details at http://www.wescottdesign.com/actfes/actfes.html
:-)
Gerhard
Boeing was pushing the DATAC system (also known as ARINC 629) as a follow-on to the MIL STD-1553. It **does** have guaranteed response time. As well as the Noise immunity of 1553.
Don't know how well it has been adopted but this reference claims it doesn't have much support.
Aeroflex makes transceivers and there seems to be a chipset from National.
Robert
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