2009 March

March 2009


The Eagle PCB design files are now available for download from the Strobit Project Page.  Constructive feedback is appreciated.  Please treat these as an early alpha release, the PCB has not yet been verified.

I have also released the design files for a blank personality board, this can be used as a starting point for any future boards.

I will shortly have an early release of the Basic Strobist Personality board online.

As mentioned in a previous post, Bill Grundmann has been documenting his investigation into Canons E-TTL protocol.  Bill has just released a PDF summarising what he has found so far.

I’ve yet to go over it in detail, but for those looking at doing some E-TTL investigation of their own this document is a must.

http://billgrundmann.files.wordpress.com/2009/03/ettl_grundmann.pdf

The Strobit Project now has some Google groups enabled.  Feel free to join these and take part in the discussion.  I will leave the old forums up for archival/historical purposes, but will become read only eventually.

See Strobit Project Page for the groups.

As one does while in bed at 3am and unable to sleep, I was thinking of the Strobit Triggr (which is probably why I couldn’t get to sleep in the first place) an idea presented itself for Arduino type shields (in particular Strobit Triggr personality boards) where they could be given some real personality.

Currently Arduino shields provide the hardware interface to the world for the base Arduino board.  On the Arduino resides the code that provide the functionality i.e the personality, in the form of a sketch.  The sketch and the shield have a one to one mapping, i.e. a sketch for one shield will not work with another shield type and visa-a-versa.  So whenever a shield is changed, the base Arduino boards needs re-programming with a new sketch to give it it’s personality from the host PC/MAC this provides the new functionality associated with the shield.

The idea is for the shields to have onboard flash memory that contains the actual Arduino sketch associated with it.  When the Arduino is powered up, it then checks for this flash first, if present then it proceeds to load  from here, reprogramming itself with the new code, reboots and now has the functionality associated with the shield.  If there is no flash available (a shield with no personality e.g. current shields) then the Arduino proceeds to load as per normal.

This way you could easily swap a shield/personality board without having to reprogram the Arduino, it keeps the functionality of the shield with the shield, thus giving shields a personality.

As “Everything Robotics” just doesn’t seem to cut it anymore (I can just here the comments as people stumble across the site “hmm not much robotics happening here”). 

The blog now has a new name “Strobotics” (Stro-botics) which seems to reflect the content a little better don’t you think?

A new domain strobotics.com.au is now active, but the site is still pointing to the old domain for the time being.  I will eventually move everything over to the new domain,  I will however keep all domains pointing to this site indefinitely.

The Strobit Triggr project now has a proper open source home, a Google Code project page – http://code.google.com/p/strobit/ If you think you can contribute please join the project.

Over the next few days as time permits, I’ll be adding everything I have so far to source control for the current design.

All hardware will fall under the TAPR Open Hardware License – http://www.tapr.org/ohl.html

More success from Bill Grundmann in his attempt to decrypt Canons E-TTL protocol !

It appears that there is a consistent 4msec delay between when the CLK signal from the camera body drops to GND and when the actual flash is triggered.  This would give us plenty of “leeway” in our timing to sync with the shutter I would guess.

Then next part of the puzzle is to now trick the body that it has a flash in high speed sync mode attached to achieve some high sync rates.

Next week I’ll start investigating this further (already got a pretty busy weekend on the cards )

For those of you that shoot Nikon, it might be worth looking at what Bill has done so far and see if those with knowledge can do the same for the Nikon protocol.  With the knowledge of both major protocols we just might be able to have both vendors protocols talking to each other via the Strobit Triggr.

Well done Bill and keep up the great work!

Bills’ Post: http://billgrundmann.wordpress.com/2009/03/19/canon-ettl-protocol/

Seeing as I’m a canon person as far as bodies and lens goes I thought I’d look into the E-TTL protocol and how the camera body and the flash can talk to each other.

I’m not looking to completely implement the E-TTL protocol in the Strobit Triggr, (well not yet anyway), but more along the lines of fooling the camera body that I have an E-TTL capable strobe attached and thus enable high speed sync mode.  If we know what the sequence is between the camera and the flash is, then  I can play around with the timing of the Strobit Triggers.  Why do we need to do this?

  1. By not using E-TTL we are then limited to standard hotshoe only sync speeds,  so when the camera triggers the hotshoe we are at least guaranteed 1/60 – 1/250 etc rather than some higher sync speeds like 1/1000 or more.
  2. Wireless as a transmission medium has some inherent lag due to the physical properties (i.e. air) so if we can fool the camera I have a high speed strobe attached and so enable high speed sync mode, the camera triggers will still be out of sync due to this lag.  So with some knowledge of the basic E-TTL sequence and by playing around with the timing I should be able to get the Strobit Triggrs to fire early, before the actual camera fires and still be in sync with the high speed shutter.

While I’m waiting for the boards I will look at playing around with this idea, I’ve just ordered a cheap canon E-TTL flash extension cord (http://www.dealextreme.com/details.dx/sku.19612) so I can gain access to the hotshoe contacts easily with my logic analyser. 

Unfortunately one of my biggest stumbling blocks is that I do not own or have access to a Canon E-TTL flash, (the only non canon equipment in my kit are my strobes mix of Nikon and Vivitar), thus started some research, it just so happens that Bill Grundmann has recently started his analysis of the E-TTL protocol and making fantastic headways.  Dang he has saved me a huge amount of time!  Well done Bill!

I’ve put all the newer components online, sketchup models are now in googles 3d warehouse and Eagle3D added to the existing library.

(more…)

Here are the final renderings from POV with the basic personality board installed, along with a 900MHZ antenna.  I’m pretty happy now, looks OK and now will see how accurate this exercise really is when I get prototype boards back.

triggr-010

triggr-010

triggr-010

triggr-010

triggr-010

triggr-010

triggr-010  triggr-010

Some more components added to the Strobit Eagle3d Library.  Can be found here.

Sparkfun SMA PCB Edge

SMA_FEMALE_PCB3.5mm Phone Jack SMD

PJ326

Ok not quite finished, but almost there!  I’ve had to make a few minor changes.  I’m glad I’ve taken the time to learn and play around with Eagle 3D, it had highlighted some potential clearance problems.  Rather than rush things I’ve decided to take a bit of time modelling than fork out my $$$ and get some prototypes made only to find these problems down the track and could have avoided.  Granted Modelling is not a silver bullet, and I guess I could be here forever, but now I’m a lot happier.

Changes:

  • Moved SMA antenna connector back from front edge of the PCB as it was hanging over slightly.  This connector is optional at assembly.  The pad can be used to solder on a wire antenna instead.
  • Changed switched power side on the switch, The switched side of the On/Off switch was very close to ground plane coming under the switch so had the potential to short, now is nice and clear.  I’ve also added some more ground plane clearance around the switch contacts just to be on the safe side.
  • Added solder jumpers for LEDS, probably don’t want these enabled if a personality board is on, but it gives you the option to use them or not, and re-use the I/O if required.
  • Moved vias and tracks away from standoffs.

Todo:

  • I think I really need to isolate the 2 power sources from each other, i.e. the Power from the USB and VBAT, so I’m looking at putting in a BAT54C barrier diode.  Just need to research it a bit more.
  • Still don’t know what to do with the ICSP connector.  I will probably leave it there with the option of putting it on at assembly.  I’m pretty sure that it will clear any personality board with a bit of care.  Modelling the personality board is my next step.

triggr-010

Strobit Eagle3D Library now available for download….see Eagle3D Page

HopeRF 433Mhz / 915Mhz

triggr-010

Experimental 2.4GHZ

triggr-020

I’ve been playing around with Googles sketchup over the weekend and have created some components, one the RFM12B module and a basic camera hotshoe to scale.  It’s been a great little exercise in learning both Alibre and Sketchup as I’ve been wanting to get some 3D modelling practice, I’m finding that it’s easier to create things in Alibre and then export them to Sketchup.  Alibre does not support texture mappings in the drawing or export to POV, but Sketchup does it brilliantly, while on the other hand, Alibre’s3D modelling is very easy to use.

Currently the workflow is:  Model in Alibre –> textures in Sketchup – > POV Rendering– > Eagle3D Components.

Keep an eye out for more to come.  I’ve started a Stobit Collection in Googles 3D warehouse  for use with this project and will be adding to it as I go.   I’ll be putting the Eagle3D component files that I’ve created online shortly.

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