Using USB remote V2 with an RC receiver

nedhorning

5

« on: 15 / October / 2012, 11:27:05 »

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Hi – I'm new to CHDK and am trying to take advantage of some of the new functionality provided by USB remote V2. I want to trigger two cameras (one visible and one near-infrared) simultaneously using an RC signal. I am currently able to do that by hooking up a switch to my RC receiver and setting the CHDK Remote Parameters to detect on/off voltages. My goal is to be able to eliminate the switch and interpret the pulse information directly from the RC receiver. My understanding is that the pulse width for my receiver ranges from under 1ms to about 2ms and I haven't been able to figure out how to record that information using get_usb_power. The pulse width readings I'm getting are sporadic and much larger (~10 and greater) then I would expect and they don't seem to change when I change the pulse width on the RC transmitter. Is it possible to get sufficient precision to detect the changes I'm looking for (<1ms and > 1ms?

It's possible I have the USB wired wrong [RC signal (white) => usb negative (black) and RC + (red) => usb + (red)] but if that's the case I'm not sure how to fix it.

Is there anyone out there using USB remote V2 and reading the pulse width from an RC receiver? Any suggestions?

I have a Canon A2200 and am using CHDK-a2200-100d-1.1.0_BETA.

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waterwingz

12140

Re: Using USB remote V2 with an RC receiver

« Reply #1 on: 15 / October / 2012, 11:56:33 »

Quote from: nedhorning on 15 / October / 2012, 11:27:05

Is it possible to get sufficient precision to detect the changes I'm looking for (<1ms and > 1ms?

No.

CHDK "polls" the USB state every time the keyboard task runs. By default that's 10mSec so your pulse will only be detected if it happens to be active when the task runs. Pulses shorter than 10 mSec will be sometime caught and sometimes missed.

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nedhorning

5

Re: Using USB remote V2 with an RC receiver

« Reply #2 on: 15 / October / 2012, 13:45:29 »

Thanks for the quick reply.

Would it be worth adding the polling rate information to the USB Remote Wiki? The Wiki currently has “For more complex operations, devices that produce multiple pulses or pulses of different time duration (width) can be used. These are popular with radio controlled airplane enthusiasts and kite aerial photographers.” This is a little misleading since RC equipment works with a pulse width that is too short to be reliably detected.

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waterwingz

12140

Re: Using USB remote V2 with an RC receiver

« Reply #3 on: 15 / October / 2012, 13:59:53 »

Quote from: nedhorning on 15 / October / 2012, 13:45:29

Would it be worth adding the polling rate information to the USB Remote Wiki? The Wiki currently has “For more complex operations, devices that produce multiple pulses or pulses of different time duration (width) can be used. These are popular with radio controlled airplane enthusiasts and kite aerial photographers.” This is a little misleading since RC equipment works with a pulse width that is too short to be reliably detected.

I added a timing note yesterday but I really need to add a timing diagram too.

The comment about RC plane and KAP referred to the adapters you can get from the folks at http://www.gentles.ltd.uk/ (and presumably others ?). Sorry if it was misleading.

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Ported : A1200 SD940 G10 Powershot N G16