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Hijack - iPhone Sensors Thru Audio Jack

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Re: Hijack - iPhone Sensors Thru Audio Jack

#21

Post by jonsen »

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…

The tone AC signal has to be converted to DC power supply. A higher frequency means smaller components needed to do the conversion. Size roughly inverse proportional to frequency. So they probably chose close to the highest frequency possible on the audio output.

Re: Hijack - iPhone Sensors Thru Audio Jack

#22

Post by colinloretz »

nupark2 wrote: post #11
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 dealin…

Agreed.

Using the dock connector with a legitimate product requires you to join Apple's "Made for iPhone" program.

For a device like Square that works on multiple platforms, the audio jack is a common interface and the Square reader has the benefit of requiring little (to zero) power to function as it consists of a magnetic head that works when a card slides across it.

Re: Hijack - iPhone Sensors Thru Audio Jack

#23

Post by nemik »

yabai wrote: post #16
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?

Well there is a small company that created a credit card reader using it to enable smartphones to act as Point of Sale machines. They call it "Square".

Re: Hijack - iPhone Sensors Thru Audio Jack

#24

Post by mdda »

jonsen wrote: post #21
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…

The tone AC signal has to be converted to DC power supply. A higher frequency means smaller components needed to do the conversion. Size roughly inverse proportional to frequency. So they probably chose close to the highest frequency possible on the audio output.

If the samples are put out at CD rates (44.1KHz) then 22.05KHz is the highest AC frequency available.

Re: Hijack - iPhone Sensors Thru Audio Jack

#25

Post by msutherl »

yabai wrote: post #16
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?

Prototyping mobile accessories! When you're working with hardware, building things to make things talk takes a lot of time. This makes it easier.

It's also useful for student projects. I got one of the original wiretaps when they were giving away their first batch for a prototype medical device (we didn't end up using it in the end because it was still too much work).

Re: Hijack - iPhone Sensors Thru Audio Jack

#27

Post by angusgr »

joezydeco wrote: post #14
duskwuff wrote: post #12

Earlier quoted context omitted.

"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?

Where does it say that Apple approved the cable? It seems to me like they're deliberately avoiding any step that requires Apple approval.

Re: Hijack - iPhone Sensors Thru Audio Jack

#28

Post by joezydeco »

angusgr wrote: post #27
joezydeco wrote: post #14

Earlier quoted context omitted.

But Apple approved the cable . Get the paradox?

Where does it say that Apple approved the cable? It seems to me like they're deliberately avoiding any step that requires Apple approval.

It's right on the front page.

You can't use the "Made for iPod" label on your product unless it's Apple approved and has an Apple-supplied chip in the dock connector.

Re: Hijack - iPhone Sensors Thru Audio Jack

#29

Post by joezydeco »

msutherl wrote: post #26
joezydeco wrote: post #6

The O'Reilly book "iPhone Hacks" also has schematics and details on how to create a headphone jack interface.

...which requires a Cypress PSoC chip for which you need to buy a $100+ programmer and use their Windows-only IDE.

The concept is pretty well explained (FSK mod/demod). Someone enterprising enough can implement it in ways that don't require the Cypress equipment.
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