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Hijack - iPhone Sensors Thru Audio Jack

seeedstudio.com

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Re: Hijack - iPhone Sensors Thru Audio Jack

#11

Post by nupark2 »

bwarp wrote: post #10

I think this is a novelty at best. The electrical interface standards may change between devices (voltage/current sink ability) and even between software releases (power saving etc) resulting in a sudden "it stops working" moment. The basis of it is also flawed on the fact that it's a workaround for a closed platform at which point it's probably better to just use an open one. Hack yes. Novelty yes. Don't build anyth…

Harvesting power is a bit questionable, but in terms of an input mechanism, Square built their reader on the idea.

As far as it being a hack for a closed platform, I'm not sure why that matters if your goal is to interface with the primary mobile phone platforms. This solution works, and if you need something more professional, working with the dock connector itself isn't an burden any more insurmountable than dealing with injection molding or other product design and manufacturing concerns.

Re: Hijack - iPhone Sensors Thru Audio Jack

#12

Post by duskwuff »

joezydeco wrote: post #8
automach wrote: post #4

Earlier quoted context omitted.

Using the Dock connector involved paying Apple a licensing fee. This circumvents that, and it's similar (although more involved) to how Square's card readers work. There is already an iOS serial cable though, which I would think would be a better option for many projects: http://redpark.com/c2db9.html

" Under current Apple policy this cable may not be used with apps sold on the App Store." That's an odd condition of Apple's terms. Why is this so? If I go through the process of designing and approving a hardware device, I can't sell an app to go with it? Or do I have to provide the app in tandem with the device?

"may not be used with apps sold on the App Store" probably just means "Apple will not approve an application which uses this cable for sale on the App Store".

Re: Hijack - iPhone Sensors Thru Audio Jack

#13

Post by feralchimp »

The HiJack energy harvester can supply 7.4 mW to a load with 47% power conversion efficiency when driven by a 22 kHz tone from the output of a single audio channel through the iPhone/ipad/itouch headset port, no extra energy source is needed. The name "Hijack" refers to this energy harvestign method.

Can someone here explain the functional significance of the 22kHz tone? It would be more intuitive if they'd said "an audio signal driven at the headphone port's maximum volume." Why would there be more harvestable energy in a max-volume 22kHz tone than a max-volume 11kHz tone? Or might this be to avoid accidentally blasting the user with a super loud output tone (i.e. in a more audible range) from the device speaker?

Re: Hijack - iPhone Sensors Thru Audio Jack

#14

Post by joezydeco »

duskwuff wrote: post #12
joezydeco wrote: post #8

Earlier quoted context omitted.

" Under current Apple policy this cable may not be used with apps sold on the App Store." That's an odd condition of Apple's terms. Why is this so? If I go through the process of designing and approving a hardware device, I can't sell an app to go with it? Or do I have to provide the app in tandem with the device?

"may not be used with apps sold on the App Store" probably just means "Apple will not approve an application which uses this cable for sale on the App Store".

But Apple approved the cable. Get the paradox?

Re: Hijack - iPhone Sensors Thru Audio Jack

#15

Post by antirez »

great idea / technology, lame page. Would love to see a decent article on the topic, with specifications about the minimal number of components to do something useful (enough to use the input jeck ADC in a decent way), and some example application that you can actual build easily with schematics. IMHO a good show case could be a termometer that you can plug to your iphone with minimal components, using a classic temperature sensor that changes the resistance with difference of temperature.

Re: Hijack - iPhone Sensors Thru Audio Jack

#16

Post by yabai »

bwarp wrote: post #10

I think this is a novelty at best. The electrical interface standards may change between devices (voltage/current sink ability) and even between software releases (power saving etc) resulting in a sudden "it stops working" moment. The basis of it is also flawed on the fact that it's a workaround for a closed platform at which point it's probably better to just use an open one. Hack yes. Novelty yes. Don't build anyth…

Looks interesting...but what is the real application?

Re: Hijack - iPhone Sensors Thru Audio Jack

#17

Post by acgourley »

feralchimp wrote: post #13

The HiJack energy harvester can supply 7.4 mW to a load with 47% power conversion efficiency when driven by a 22 kHz tone from the output of a single audio channel through the iPhone/ipad/itouch headset port, no extra energy source is needed. The name "Hijack" refers to this energy harvestign method. Can someone here explain the functional significance of the 22kHz tone? It would be more intuitive if they'd said "an…

It's probably no coincidence it's right out of human hearing range. Most headphone drivers response curve are likely designed to be less efficient at that freq, and thus need more power to create the same loudness. the iPhone's audio driver probably takes this into consideration and drives those frequencies with more power to compensate.

Just a guess, I'm sure they arrived at it purely through trial and error, and were happy to find that it's also a frequency that will be minimally annoying if a headphone happens to be plugged in when the tone is played.

Re: Hijack - iPhone Sensors Thru Audio Jack

#19

Post by tekromancr »

acgourley wrote: post #17
feralchimp wrote: post #13

The HiJack energy harvester can supply 7.4 mW to a load with 47% power conversion efficiency when driven by a 22 kHz tone from the output of a single audio channel through the iPhone/ipad/itouch headset port, no extra energy source is needed. The name "Hijack" refers to this energy harvestign method. Can someone here explain the functional significance of the 22kHz tone? It would be more intuitive if they'd said "an…

It's probably no coincidence it's right out of human hearing range. Most headphone drivers response curve are likely designed to be less efficient at that freq, and thus need more power to create the same loudness. the iPhone's audio driver probably takes this into consideration and drives those frequencies with more power to compensate. Just a guess, I'm sure they arrived at it purely through trial and error, and we…

Minimally annoying my ass. If you are still young enough to hear it it's downright painful!

Re: Hijack - iPhone Sensors Thru Audio Jack

#20

Post by mirkules »

tekromancr wrote: post #18

I suppose you could use this to make a generic ir remote. That was one of the coolest things that all my old palm PDAs could do, and has always been a big dream feature on the iPhone.

That has already been done: http://rtfms.com/episode-4-turn-your-iphoneandroid-mac-pc-pl... albeit without HiJack
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