USB-Remote Voltage? - Hotwire! Hardware Mods, Accessories and Insights - CHDK Forum
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USB-Remote Voltage?

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Offline Sasha

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USB-Remote Voltage?
« on: 21 / October / 2009, 15:36:12 »
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How much is the voltage required for the USB remote to let Chdk release the camera?

I'd like to release a camera from a Linux PDA using an USB connection. As discussed
in this topic: http://chdk.setepontos.com/index.php/topic,4338.0.html
it seems possible not only to release a camera using PTP, but also sending
generic messages via PTP. Chdk could receive it's complete configuration from
a PDA application with a convenient user interface. So that's the idea, but:

A PDA with Linux would be required: http://www.trisoft.de/en_freerunner.htm
It could deliver 100mA to the camera. So the question is: would a standard
Desktop PC download images from the camera with 100mA? Or is this too low?
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Offline whim

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Re: USB-Remote Voltage?
« Reply #1 on: 21 / October / 2009, 15:52:59 »
Quote
How much is the voltage required for the USB remote to let Chdk release the camera?
mostly ~ 3 - 4.5 V, you can find data for some cams on the Wiki Camera Features page:
http://chdk.wikia.com/wiki/CameraFeatures

hth,

wim
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Offline Microfunguy

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Re: USB-Remote Voltage?
« Reply #2 on: 21 / October / 2009, 15:56:56 »
Quote from: Sasha on 21 / October / 2009, 15:36:12
would a standard Desktop PC download images from the camera with 100mA?

You do not need even 1 mA.

The USB V+ is just a logic signal that tells the camera a USB connection is made.

The PDA does not power the camera.


David
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Offline Sasha

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Re: USB-Remote Voltage?
« Reply #3 on: 22 / October / 2009, 13:46:45 »
According to the technical specification it does:

"USB Client/Hostport. Hostport with 100mA Output to use simple USB client devices."

The question however is, would this be enough to run 2 or more cameras?
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Offline Microfunguy

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Re: USB-Remote Voltage?
« Reply #4 on: 22 / October / 2009, 15:07:54 »
Quote from: Sasha on 22 / October / 2009, 13:46:45
According to the technical specification it does:

Suit yourself  ......

If you know anything about electronics there is a VERY simple way to find-out.

Measure the resistance (in kilohms) across the USB V+ and V- connections on the camera.

Divide 5 by that value to get required current in mA.

I GUARANTEE it will be VERY  small.

People have operated eight cameras without any problem.
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Offline fbonomi

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Re: USB-Remote Voltage?
« Reply #5 on: 23 / October / 2009, 04:29:20 »
Quote from: Sasha on 22 / October / 2009, 13:46:45
According to the technical specification it does:

The technical specification of what?

If it's the specs of the PDA, then the specs just say "the pda would be able to give 100ma"

The fact here is that the camera is not taking them, otherwise we could recharge our cameras by connecting them to the PC USB.
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Offline Pauls9

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Re: USB-Remote Voltage?
« Reply #6 on: 23 / October / 2009, 05:21:47 »
Quote from: fbonomi on 23 / October / 2009, 04:29:20
Quote from: Sasha on 22 / October / 2009, 13:46:45
According to the technical specification it does:

The technical specification of what?

If it's the specs of the PDA, then the specs just say "the pda would be able to give 100ma"

The fact here is that the camera is not taking them, otherwise we could recharge our cameras by connecting them to the PC USB.
Absolutely. Many USB devices take power from the host (the pda in your case), since they don't have a separate supply. Your pda can supply up to 100 milliamps of current should the connected device need it. In this case, the camera has its own supply and doesn't take any noticeable current from the USB host. In other words, yes, your pda or PC will be able to do what you want.
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Offline Sasha

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Re: USB-Remote Voltage?
« Reply #7 on: 23 / October / 2009, 16:40:49 »
Thank you all for your expertise and Pauls9 for a comprehensible roundup.
Though I know at least a little about electronics, I simply have no equipment
to measure anything at all. But that's all good news you bring:
So the camera does supply a minimum amount of voltage to the USB port
in order to establish a data transfer. But it can't power any devices itself,
just like a Bluetooth stick plugged into the camera.

I assume this wouldn't work. But could this Bluetooth device (with USB profile)
get externally powered by a battery pack, perhaps? Some kind of USB double-plug
between camera and Bluetooth device would feed in current.
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Offline Microfunguy

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Re: USB-Remote Voltage?
« Reply #8 on: 23 / October / 2009, 18:20:11 »
The camera does not generate the +5V (or whatever), the USB on your PDA provides that.
There is no problem connecting your PDA to the camera.

You would have to write a PTP programme similar to ptpcam that is mentioned in the link you referenced.
I have no idea how you do that on your Linux device.
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Offline cppasm

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Re: USB-Remote Voltage?
« Reply #9 on: 19 / November / 2009, 08:09:45 »
Quote from: Sasha on 22 / October / 2009, 13:46:45
"USB Client/Hostport. Hostport with 100mA Output to use simple USB client devices."
100mA is the maximum current for USB connection according to USB Specification.
You can use your PDA to trigger camera.
But this will be uncomfortable with USB Remote, because camera will shoot immediately when you connect it to PDA.
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