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communication protocol with name resembling 1335?

M

Mike Noone

Jan 1, 1970
0
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
 
J

Jim Thompson

Jan 1, 1970
0
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
 
M

Mike Noone

Jan 1, 1970
0
Jim said:
Probably MIL-STD-1553, used primarily in aircraft.

...Jim Thompson


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
 
J

Jim Thompson

Jan 1, 1970
0
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
 
J

John Larkin

Jan 1, 1970
0
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

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
 
N

neil

Jan 1, 1970
0
John Larkin said:
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
Neil
 
G

Gerhard Hoffmann

Jan 1, 1970
0
....

and it has guaranteed response time, unlike Ethernet CSMA/CD

Is there anything in CAN that would make it unsuitable for small aircraft?

Gerhard
 
J

Jim Thompson

Jan 1, 1970
0
...

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
 
J

Joerg

Jan 1, 1970
0
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.
Depends on the electrical noise level. What is the voltage swing in
CAN?


Regular logic levels. This shows the ranges for unipolar and
differential modes, scroll down to "CAN bus interface ICs":

http://www.interfacebus.com/Design_Connector_CAN.html
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.

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.
 
G

Gerhard Hoffmann

Jan 1, 1970
0
Depends on the electrical noise level. What is the voltage swing in
CAN?

probably less than 5V, differential. I'll look it up.
one source:
<http://www.semiconductors.bosch.de/en/20/can/index.asp>

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.

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.

Was there a reason not to go optical?

Gerhard
 
J

Jim Thompson

Jan 1, 1970
0
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":

http://www.interfacebus.com/Design_Connector_CAN.html


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.

I don't know. I just design to the spec I'm told. I'm just a dooby
;-)

...Jim Thompson
 
J

Joerg

Jan 1, 1970
0
Hello Jim,
I don't know. I just design to the spec I'm told. I'm just a dooby
;-)

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.
 
J

Joerg

Jan 1, 1970
0
Hello Gerhard,
probably less than 5V, differential. I'll look it up.
one source:
<http://www.semiconductors.bosch.de/en/20/can/index.asp>

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.

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.
 
G

Gerhard Hoffmann

Jan 1, 1970
0
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.

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.
Probably that's why so much old stuff is found in aeronautics.

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
 
J

Joerg

Jan 1, 1970
0
Hello Gerhard,
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.

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:
http://www.cameronparkkitfox.com/pictures/craig800.jpg

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.
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..

Well, the heavier a sector is regulated the longer it takes for new
things to take hold.
or the effort it took to pave the way for newfangled things like BPSK
in mode S transponder uplinks.

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.
 
J

Jim Thompson

Jan 1, 1970
0
Hello Gerhard,
[snip]

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.
[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
 
T

Tim Wescott

Jan 1, 1970
0
Mike said:
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
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
 
R

Robert

Jan 1, 1970
0
Gerhard Hoffmann said:
...

and it has guaranteed response time, unlike Ethernet CSMA/CD

Is there anything in CAN that would make it unsuitable for small aircraft?

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.

http://archive.chipcenter.com/circuitcellar/may01/c0501gn7.htm

Aeroflex makes transceivers and there seems to be a chipset from National.

http://www.maxt.com/Product_IPM_ARINC_629_BP_overview.asp

Robert
 
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