Wireless needs a Brainstorm!

Wireless Design and Protocol Discussion

Moderators: seaton, strogg

Just a thought

Postby Rudeofus » Mon Sep 24, 2007 7:56 pm

We all realize that RF is not going to be easy. An ASK transceiver may be cheaper than PW, but I sure hope nobody expects decent performance from such a design indoors. You have to deal with huge signal fluctuations due to fading, something ASK inherently can't do unless you are allowed to transmit with lots of power (i.e. make sure that you are received much stronger than the noise / interference levels).

Personally I see two options which have realistic chances of succeeding (unless you want to do it purely for the fun value of it and performance doesn't matter):
  • Either we find some decent ready to use FM based system in the 2.4 GHz range which does not require FCC approval any more, basically a ready to use radio modem which allows us to send any data we want at high speeds (100 kBaud is certainly not too much) and with extremely low latency (which excludes Bluetooth, don't know about ZigBee)
  • Or we go the way Canon/Nikon went and use optical data transmission to control the flash. Unlike what I said about RF, with optical you can blast very high amounts of power without fearing the FCC/ETSI/ARIB/... and as long as you don't endanger anyone
In case we go with RF modems (assuming they exist and are affordable) our claim to fame would be that we can do more than any PW customer could ever do with our radio link, since we are free to define the protocol.

In case we do use optical data transmission, we could either reimplement the existing protocols (think: control a Vivitar/Sunpak flash in manual mode through your ST-E2 or whatever we replace it with) or come up with extensions that we find desireable or fun to play with. And if the range of optical doesn't please us, there's hope that if we use a protocol sufficiently similar to E-TTL, that our optical signals can be carried over long distances through the radiopopper device (which will be FCC approved by then, hopefully a european version will also come to light eventually)
Rudeofus
 
Posts: 27
Joined: Sun Sep 23, 2007 11:28 pm

Postby JonSenior » Mon Sep 24, 2007 8:02 pm

chrisb wrote:
FCC compliance is a USA thing agreed, but there are requirements for Europe and Asia, European compliance is mandated by the EMC and RTTE Directive, Asia is regulated by individual countries, Australia - ACMA, Japan - VCCI.


True, but (AFAIK) European compliance requires compliance with the given regulations, not testing on a per-product basis. This means that as long as we don't put more than the specificied levels onto an aerial (i.e. No yagi aerials and inline signal amplifiers) there is no problem with building a new product.

Disclaimers: I can't speak for other regulatory bodies. I am not a lawyer. This was the case when I played with RF around about 3 years ago.

Jon
JonSenior
 
Posts: 60
Joined: Fri Sep 21, 2007 7:27 pm
Location: Paris, France

Postby brittonphotography » Mon Sep 24, 2007 8:03 pm

chrisb wrote:the unit will still need FCC Part 15 testing and you are responsible for testing it even if you provide it as a kit - you are providing a product to an end user.

If the RF transmitter/receiver is already approved, then the process is easier as you don't have to apply for an FCC ID and obtain radio approval for the RF portion.

Regardless of the approval on the RF side, you are still required to get the whole unit tested to FCC Part 15 (this would be a Part 15 Class B device).

-chris


Can you provide a link/ more info /pricing on fcc part 15b testing, and what that would involve for a FCC cleared Xbee module for example?
brittonphotography
 
Posts: 25
Joined: Fri Sep 21, 2007 8:52 pm

Re: Just a thought

Postby MQ » Mon Sep 24, 2007 8:05 pm

Rudeofus wrote:[*]Or we go the way Canon/Nikon went and use optical data
transmission to control the flash. Unlike what I said about RF,
with optical you can blast very high amounts of power without
fearing the FCC/ETSI/ARIB/...


Veto. Especially in high ISO settings with aperture wide open
the control flash will turn visible and ruin the image.

Shooting at ISO 1600 with flash at 1/256 manual power
and aperture wide open is a regular move for me.

With the new Canon Mark III displaying the same noise
at 3200 ISO as the Mark II did at 1600 ISO, this will
increasingly be relevant in daily use.
If you are not part of the solution,
you are part of the problem.
MQ
 
Posts: 26
Joined: Sun Sep 23, 2007 8:32 am
Location: Germany

Postby chrisb » Mon Sep 24, 2007 8:51 pm

JonSenior wrote:True, but (AFAIK) European compliance requires compliance with the given regulations, not testing on a per-product basis. This means that as long as we don't put more than the specificied levels onto an aerial (i.e. No yagi aerials and inline signal amplifiers) there is no problem with building a new product.

Disclaimers: I can't speak for other regulatory bodies. I am not a lawyer. This was the case when I played with RF around about 3 years ago.

Jon


The European EMC directive deals with a concept of "placing on the market", under this definition then anyone building a product for their own use from directions off the internet wouldn't need to test the product. However, the relevant authorities (especially the UK) could consider that you are creating a product using CE marked sub assemblies (the RF unit), and therefore you would be subject to the directives. (This is an area that I haven't had to deal with before so I'm not sure of the exact requirements).

Anyone building the unit for someone else, (even if it's a one off), is required to test it. The same rules apply if you are providing a kit - the EU terms it as a system.

As far as specified output levels for antennas, this is generally covered under the R&TTE directive. Suppliers of RF modules will already have tested their devices for compliance with this directive and as such this portion would not affect a person using the device in a home brewed unit.

-chris
chrisb
 
Posts: 7
Joined: Mon Sep 24, 2007 1:04 pm

Postby chrisb » Mon Sep 24, 2007 8:57 pm

brittonphotography wrote:
chrisb wrote:the unit will still need FCC Part 15 testing and you are responsible for testing it even if you provide it as a kit - you are providing a product to an end user.

If the RF transmitter/receiver is already approved, then the process is easier as you don't have to apply for an FCC ID and obtain radio approval for the RF portion.

Regardless of the approval on the RF side, you are still required to get the whole unit tested to FCC Part 15 (this would be a Part 15 Class B device).

-chris


Can you provide a link/ more info /pricing on fcc part 15b testing, and what that would involve for a FCC cleared Xbee module for example?


You would be looking at between 5 to 10k (US$). The exact cost would depend on a couple of things;
Do you pass the first time?
Do you just want FCC or is Europe and Australia part of the testing.

European testing covers more than the FCC does. The FCC just look at what is being radiated from your unit, i.e., emissions, Europe looks at what is being radiated from the unit and also how you respond to radiation being directed at you unit and how well you can handle ESD, i.e., immunity.

-chris
chrisb
 
Posts: 7
Joined: Mon Sep 24, 2007 1:04 pm

Re: Just a thought

Postby Rudeofus » Mon Sep 24, 2007 10:19 pm

MQ wrote:Veto. Especially in high ISO settings with aperture wide open
the control flash will turn visible and ruin the image.


Point taken. But since we don't plan on putting together a flash/transmitter combo, we have no reason to trigger with visible light. IR is cheaper and works quite well. You can pulse trigger IR-LEDs pretty hard, too, so we may get away even without a flash tube (not sure).

Also, if even IR light destroys your shots, those radiopoppers might save the day (just cover the trigger unit)
Rudeofus
 
Posts: 27
Joined: Sun Sep 23, 2007 11:28 pm

Re: Just a thought

Postby peter_gullberg » Tue Sep 25, 2007 4:46 am

Rudeofus wrote:[...]
[list][*]Either we find some decent ready to use FM based system in the 2.4 GHz range which does not require FCC approval any more, basically a ready to use radio modem which allows us to send any data we want at high speeds (100 kBaud is certainly not too much) and with extremely low latency (which excludes Bluetooth, don't know about ZigBee)
[...]


Unfortunately it seems that you can exclude ZigBee, because the realtime performance seem to be too slow, in the +millisecond range to forward a message.
http://www.rtcmagazine.com/home/article.php?id=100656
peter_gullberg
 
Posts: 4
Joined: Sun Sep 23, 2007 8:34 pm
Location: Gothenburg, Sweden

Re: Just a thought

Postby JonSenior » Tue Sep 25, 2007 5:28 am

peter_gullberg wrote:Unfortunately it seems that you can exclude ZigBee, because the realtime performance seem to be too slow, in the +millisecond range to forward a message.
http://www.rtcmagazine.com/home/article.php?id=100656


The image that demonstrates this includes full return of acknowledgement packet and doesn't specify the data quantity. According to the spec sheet I have for the xBee, it looks like we can force data transmission on our cue. Not sure what the latency will actually be though. If you have an idea based on the specs or real life experience, then please add it to the Hardware page on the wiki.

Jon
JonSenior
 
Posts: 60
Joined: Fri Sep 21, 2007 7:27 pm
Location: Paris, France

Postby philtulju » Tue Sep 25, 2007 8:36 am

Agree that avoiding optical / LED communication makes sense - I mean, we already have that available, no?
(BTW, I think the comment about control flash being visible WAS referring to IR - cameras have IR filters, but they can still see it somewhat - try looking at the IrDA port on your computer with your cell phone camera, e.g.)

I see no conflict between low cost / complexity and reliability. There are lots of ICs avalable with most of the RF chain ready to go. The PWs use FSK with a dead-simple protocol. While it would be infringement and unethical to pinch LPA's exact design, they have gotten a number of things right.

From my reading of their patents and documentation, they basically use a code-division scheme. CDMA phones use something similar, but it is more complex, since they have these orthogonal matricies, etc. Basically, the advantage of this scheme is that is presumes interference. All the devices use the whole (radio) bandwidth of the channel in an unscheduled and uncoordinated way. The "channels" for PWs are just different codes. When it is time to fire, the transmitter shoots out a very short "sentence" of FSK data. This is like saying, "Hey Joe!" Then Joe pulls the trigger. Everyone who is not Joe ignores it.
By doing this, you have extremely low duty cycle allowing you to bump up the instantaneous power, and the larger (radio) bandwidth increases your link budget. All together, you have a low power, long distance, reliable link. Because the data sentence is short, you also have, critically, low latency. While LPA has a patented design, these principles are well known and could be used.

By implementing some of these kind of modulation schemes in a uC, we can just bang out any old protocol on the air, and the RF part can be KISS.

philtulju
philtulju
 
Posts: 6
Joined: Mon Sep 24, 2007 4:38 pm
Location: Shanghai, China

Archive Point

Postby Thonord » Tue Sep 25, 2007 2:07 pm

-------------------------Archive Point-----------------------------
Thonord
 
Posts: 50
Joined: Fri Sep 21, 2007 2:32 pm
Location: Norway

Archive point

Postby Thonord » Tue Sep 25, 2007 10:34 pm

Sorry, Forgot to explain.
I have taken copy of all entries in the thread and am compiling a compressed version.
I will either post it in the forum or the wiki, ask that all "contributers" review and correct as they see fit.I have found that this makes easier for everyone to use to agree upon a conclusion of the brainstorming.
Archive point was just a mental note to my self. It has no other meaning.
I will compile any further posts and add them as well.
I'm also looking at the other threads elsewhere in the forum and will include what I think is relevant.

What you'all do with the compiled list is up to you.
Tom
Ppl who agree need normally not reply, those who disagree or have questions do.
Or - just ignore me.
Thonord
 
Posts: 50
Joined: Fri Sep 21, 2007 2:32 pm
Location: Norway

First draft Brainstorming Compilation

Postby Thonord » Wed Sep 26, 2007 9:12 am

Has been posted on the wiki under Discussion.

Pls Note. This is my second entry in a Wiki ever.
Feel free to move it, format it better etc.
Feel free to delete it, if you dare :twisted:

Tom
Ppl who agree need normally not reply, those who disagree or have questions do.
Or - just ignore me.
Thonord
 
Posts: 50
Joined: Fri Sep 21, 2007 2:32 pm
Location: Norway

xbee volume discount

Postby brittonphotography » Wed Sep 26, 2007 11:50 pm

XBee OEM Modules (Zigbee/802.15.4)

http://www.maxstream.net/products/xbee/ ... zigbee.php

XBee, 1mW, wire antenna, chip antenna, or U.FL ant connector



Part no:

XB24-AWI-001 (wire antenna)

XB24-ACI-001 (chip antenna)

XB24-AUI-001 (U.FL ant connector)



Price:

1 – 99 units: $19 each

100 – 999 units: $17.80 each

1K – 9999 units: $15.25 each

10K – 24999 units: $14.20 each


XBee-PRO OEM Modules (Zigbee/802.15.4)

http://www.maxstream.net/products/xbee/ ... zigbee.php

XBee, 100mW, wire antenna, chip antenna, or U.FL ant connector



Part no:

XBP24-AWI-001 (wire antenna)

XBP24-ACI-001 (chip antenna)

XBP24-AUI-001 (U.FL ant connector)



Price:

1 – 99 units: $32 each

100 – 999 units: $28 each

1K – 9999 units: $24.50 each

10K – 24999 units: $22.50 each
brittonphotography
 
Posts: 25
Joined: Fri Sep 21, 2007 8:52 pm

Previous

Return to Wireless

Who is online

Users browsing this forum: No registered users and 1 guest

cron