USB Remote/Synchronization Problems A 2300

AmNullpunkt

4

USB Remote/Synchronization Problems A 2300

« on: 02 / November / 2016, 19:13:16 »

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Dear CHDK-community,

I just bought two powershot A2300 cameras with the intention to USB-remote/sync them for a bookscanner-project. I applied "Method 2 - Using CHDK itself to make the SD card bootable" sucessfully. Both Cameras are responding now to the USB-signal.

The problem although is, that the synchonization is far from accurate. The fact is, that they even switch priority randomly (sometimes the first, sometimes the second camera shoots first). Between both shots there happens to be a gap of around one second. In some cases only one camera fires.

I tried all the ways of changing parameters in the USB-remote-menu to get both cameras synchonized, bu didn't have any success. Can anyone help me with this problem? Could the difference of the Firmware of the two Cameras be the issue (one is 100e, the other 100f)?

Thank You!
Best regards

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waterwingz

12140

Re: USB Remote/Synchronization Problems A 2300

« Reply #1 on: 02 / November / 2016, 19:33:06 »

It would be useful to know exactly how you setup each menu options in the CHDK Remote Menu.

It would also be useful to understand what you are using for a trigger? A manual switch or something computer controlled? Can you post your wiring diagram?

How long does the +5V signal stay on before it turns off. Could it be that you are triggering a shot before both camera have had time to focus and set exposure?

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Ported : A1200 SD940 G10 Powershot N G16

AmNullpunkt

4

Re: USB Remote/Synchronization Problems A 2300

« Reply #2 on: 03 / November / 2016, 09:03:53 »

Yes, that is just what it seems so me: one camera tends to fire, while the other is still choosing the settings. So I understand: there is a minimum amount of time, that the power needs to stay on the port?

1. Menue is configured the following way:
Enable Remote - yes
Switch Type - one push
Control Mode - Quick
Enable Synch - yes
Synch Delay 0,1ms - no, 100
Enable script start - no

2. So far the triggering is just done by bare wires (for configuration see diagram). Actually I only wanted to test the system before transfering it to a permanent structure. The power source is a USB-charger.

diagram.jpg (128.11 kB, 569x1716 - viewed 41 times.)

« Last Edit: 03 / November / 2016, 11:59:10 by AmNullpunkt »

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waterwingz

12140

Re: USB Remote/Synchronization Problems A 2300

« Reply #3 on: 03 / November / 2016, 09:14:34 »

Quote from: AmNullpunkt on 03 / November / 2016, 09:03:53

Control Mode - Quick

There's the problem - use Control Mode = Normal rather than Quick.

When you use Quick, CHDK tries to release the shot as soon as the +5V is seen. The camera(s) then focus, set exposure, and shoot. It's a race to see which one is faster.

When you use Normal, CHDK will focus and set exposure when the +5V is seen. But it won't release the shutter until the +5V goes away. You will get much better sync this way. Make sure you hold your two wires together for a couple of seconds before pulling them apart and you will see the difference.

Quote

Enable Synch - yes

This will cause Normal mode to sync the shots within a few milliseconds. The only drawback is that the LCD display turns off when the shot starts (i.e. +5V goes active). If you turn it off you will be able to see the LCD throughout the shot but your sync difference might be 100 mSec or more. Try it both ways and see what you prefer?

« Last Edit: 03 / November / 2016, 09:17:47 by waterwingz »

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Ported : A1200 SD940 G10 Powershot N G16

AmNullpunkt

4

Re: USB Remote/Synchronization Problems A 2300

« Reply #4 on: 03 / November / 2016, 10:08:00 »

Thanks. That helped. Mainly, i figured out now, the time the power stays on, is the issue.If I wait for the screens to go black, i get constant results. This is great, but brings me to another problem:

In my scanning applikation i would like to run through a whole book without having to think about the time, that the release button has been pressed. Failure during the scan would be a nightmare and I won't be able to see the screens during the process. So is there any way to make the release a totally safe issue, that means: a one-contact-release only?

Could I achieve this , if I disable autofocus (I unterstand, that CHDK can make me focus manually?)? Or would this bring me only closer, that is, make the delay shorter, but still dependend on the time, that the camera needs to adjust?

Otherwise the only possibility I see would be a second circuit with a time switch, to make sure about a constant release.

« Last Edit: 03 / November / 2016, 11:26:30 by AmNullpunkt »

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reyalp

14117

Re: USB Remote/Synchronization Problems A 2300

« Reply #5 on: 03 / November / 2016, 16:00:37 »

Quote

Could I achieve this , if I disable autofocus (I unterstand, that CHDK can make me focus manually?)? Or would this bring me only closer, that is, make the delay shorter, but still dependend on the time, that the camera needs to adjust?

This seems like a good application for the "hold down half press, click full" approach.

The exposure, focus etc are all fixed after the initial half press, and each full press should trigger quickly. You can also get the same effect and possibly higher shooting rate using continuous mode, but it's a bit more complicated to control.

Waterwingz probably has a better idea of how to accomplish this using the remote code.

For book scanning, I would guess that precision sync (< a few tens of milliseconds) is not required, in which case it would be pretty easy to do with script. You could also do it with PTP control from a computer rather than the hardware remote (whether this is better depends on the rest of your application and what kinds of things you prefer to work on.)

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AmNullpunkt

4

Re: USB Remote/Synchronization Problems A 2300

« Reply #6 on: 03 / November / 2016, 17:46:34 »

Okay - I take this to be the answer: it is only possible to limit the delay via change of settings, but not to achieve a "single contact release".

Could anyone give me a short idiots guide of how to arrive at my goal to focus manually? I've found the MF-test sheet, where the a2300 is listed. But i have no idea, what this means. Actually i also don't know how to get a script running.

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waterwingz

12140

Re: USB Remote/Synchronization Problems A 2300

« Reply #7 on: 03 / November / 2016, 21:35:06 »

Quote from: AmNullpunkt on 03 / November / 2016, 10:08:00

So is there any way to make the release a totally safe issue, that means: a one-contact-release only?

What you are asking for is quite difficult physically. You are trying to make two discrete things happen (focus & shoot) in sync between two cameras with only one signal event.

One way around this is to use a script that initiates the set focus & exposure actions when the one-contact-release happens and also starts a timer. If you can show in the controlled environment of your scanner that the cameras will always complete the focus/exposure operations within a fixed time interval like 2 seconds or less, then the script will wait for that long and then release the actual shot. This is easy to do but means that you will always have that delay to wait for prior to turning the page.

Quote

Could I achieve this , if I disable autofocus (I unterstand, that CHDK can make me focus manually?)? Or would this bring me only closer, that is, make the delay shorter, but still depended on the time, that the camera needs to adjust?

That would help a lot - both cameras would fire within a few hundred milliseconds of each other at worst (my guess).

Quote

Otherwise the only possibility I see would be a second circuit with a time switch, to make sure about a constant release.

That would be even better - but the script method I mentioned above would do the same thing for "free".

Quote from: reyalp on 03 / November / 2016, 16:00:37

This seems like a good application for the "hold down half press, click full" approach.
...
Waterwingz probably has a better idea of how to accomplish this using the remote code.

This came up a few months ago. It would be quite easy to add an output control module to the USB remote code to do this. The only messy part would be deciding when to release the "half press". After a user defined delay ( range 10 seconds to two minutes maybe ?) Or maybe after two quick USB remote presses to indicate a cancel ( less that 0.5 seconds apart)?

Edit : what about USB=5V initiates the half press and then USB=0V goes to full press. If you then re-assert the 5V within 2 seconds, the sequence continues with half press held. Otherwise the half press is released and everything resets.

Quote from: AmNullpunkt on 03 / November / 2016, 17:46:34

Could anyone give me a short idiots guide of how to arrive at my goal to focus manually? I've found the MF-test sheet, where the a2300 is listed. But i have no idea, what this means. Actually i also don't know how to get a script running.

You can set focus manually using the CHDK menus. This is described in the CHDK Manual : Override Subject Distance

As far as scripting goes, there is lot's of good stuff about scripting here : CHDK Scripting Cross Reference including some good links at the top of that page.

There is also the scripting section in the CHDK Manual : Scripting

The script function you are looking for is set_focus(). Please note that the ability to accurately set focus seems to depend on the camera model and to a lesser extent on differences between the same model of camera. Testing will be required to make sure it works to your satisfaction.

If you'd like me to cobble together a script for you that does what we have discussed here just let me know.

« Last Edit: 03 / November / 2016, 22:11:48 by waterwingz »

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Ported : A1200 SD940 G10 Powershot N G16

reyalp

14117

Re: USB Remote/Synchronization Problems A 2300

« Reply #8 on: 04 / November / 2016, 02:22:03 »

Quote from: waterwingz on 03 / November / 2016, 21:35:06

This came up a few months ago. It would be quite easy to add an output control module to the USB remote code to do this. The only messy part would be deciding when to release the "half press". After a user defined delay ( range 10 seconds to two minutes maybe ?) Or maybe after two quick USB remote presses to indicate a cancel ( less that 0.5 seconds apart)?

Edit : what about USB=5V initiates the half press and then USB=0V goes to full press. If you then re-assert the 5V within 2 seconds, the sequence continues with half press held. Otherwise the half press is released and everything resets.

That seems like it should work pretty well. OTOH, if you don't need precision sync, you could just use script that presses shoot_half on startup, and has a loop that does wait click, and clicks shoot_full_only on is_key remote.

I would think +/-50 ms shouldn't matter much for book scanning, but maybe I'm missing something.

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Don't forget what the H stands for.