Does get_usb_power() ever return a value other than 0?

Old Farseeing Art

61

Does get_usb_power() ever return a value other than 0?

« on: 09 / January / 2009, 19:28:59 »

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Does get_usb_power() ever return a value other than 0? I've been trying to use this function in a Lua script but never see anything but 0. Of course, it could be that this is the 2nd Lua script I've written and I don't know what I'm doing...

Here's my code:

function print_usb_time()

repeat

   a = get_usb_power()
   print(a)
   sleep(500)
until is_key "set"

end

Searching throught the forum, I found some postings that suggest the function does not actually work. Can anyone shed some light on this for me? Thanks!!

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zeno

891

Re: Does get_usb_power() ever return a value other than 0?

« Reply #1 on: 10 / January / 2009, 05:48:15 »

You have to do two things to get a non-zero value:

1. turn on Enable Remote in Remote Parameters in Scripting Parameters
2. apply 3-5 volts to the USB port for some time (for some cameras - such as the A570 - 3 volts is not enough).

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fbonomi

469
A570IS SD1100/Ixus80

Re: Does get_usb_power() ever return a value other than 0?

« Reply #2 on: 10 / January / 2009, 06:13:35 »

the easiest voltage source to connect and test is ... your PC...

i.e., connecting the camera to the Pc and disconnecting makes a pulse.

Also, pay attention that get_usb_power measures PULSES, i.e. you have to apply voltage AND remove it.

If you just apply voltage, it will keep returning 0 until you remove voltage, and in this case it will return a value proportional to the duration of the pulse (i.e. how long you kept the voltage on)

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Jucifer

251
[A710IS]

Re: Does get_usb_power() ever return a value other than 0?

« Reply #3 on: 10 / January / 2009, 07:21:46 »

get_usb_power(1) should return 1 if usb voltage is detected (i.e. doesn't wait for the remote to be released before returning >0)

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fbonomi

469
A570IS SD1100/Ixus80

Re: Does get_usb_power() ever return a value other than 0?

« Reply #4 on: 10 / January / 2009, 08:25:40 »

oooohhh....
one never ends learning!

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Old Farseeing Art

61

Re: Does get_usb_power() ever return a value other than 0?

« Reply #5 on: 10 / January / 2009, 12:35:59 »

Great!!! Success! Now, some notes...

zeno: It was the "Enable remote" that made it work. Thanks!

fbonomi: You seem to describe correctly what my camera does.

Jucifer: You also are correct. I missed the subtle difference of what you wrote at first. The difference being
get_usb_power(1)
-versus-
get_usb_power()

With get_usb_power(1), the function reports ONLY 0 or 1; with get_usb_power(), the function reports ONLY 0 or the amount of time. And with get_usb_power(1), it updates when the level of the usb power changes whereas with get_usb_power(), it updates only when usb power goes low after having gone high.

I'm trying to clarify what I see here for other newbys like myself who may get here by searching the forum. So for a user who wants to know when usb power is applied, they should use get_usb_power(1). For someone who wants to know what the pulsewidth is, they should use get_usb_power().

On my SD1100, the command sequence to enable the remote is:

1. turn on camera

2. get in alt mode

3. press "Menu"

4. select "Miscellaneous stuff"

5. select "Remote parameters"

6. choose "Enable Remote"

7. Power off/back on: this item still selected. (I'm never sure which things get remembered and which don't after a power cycle.)

Having only the SD1100, I don't know what works on other models.

Although I searched most of the day yesterday for this information, I never found it. Does anyone know where these details are explained?

Thanks again to everyone for your help!!

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