13 ms·

It's weird how the "hardware disconnect" term for the pre-2019 devices was stretched to include a firmware, that is software-only, feature. Kinda like the "end

by est31 7y ago

It's weird how the "hardware disconnect" term for the pre-2019 devices was stretched to include a firmware, that is software-only, feature. Kinda like the "end to end encryption" of Zoom. Glad that Apple resolved this for newer devices. I'd still love to see wiring diagrams or explanations how it actually works. Which kind of circuit do they use? Is it the power line that's suppressed or the data line? Is it only an analog line that's suppressed and if you tune up internal amp you might be getting some residual? About the iPads, what does their "hardware" based microphone disconnect entail? It has to be some electro-magnetic based communication instead of currents so the circuit has to be more complicated. I doubt it's done without using any kind of software but would be glad to hear otherwise. Overall, I'm glad that they are responding to concerns and working to address them.

jwr 7y ago
> I'd still love to see wiring diagrams or explanations how it actually works. Which kind of circuit do they use? I'd like to see that too, but I don't think we will. I suspect it's a magnetic switch and I'm also curious which lines it cuts. FWIW, you can still get some audio from an accelerometer if you can get it to report data with a high enough frequency. Not sure what you mean about iPhones, their information does not mention the iPhone (and I would not expect it to).
- est31 7y ago
  > Not sure what you mean about iPhones, their information does not mention the iPhone (and I would not expect it to). I meant iPads but got confused. Thanks for pointing it out.
- derefr 7y ago
  I’d think the raw pressure-level input from the force sensors on the trackpad would be even more accurate. It’s essentially an array of transducers already.
  - markrages 7y ago
    An accelerometer on a physical object is a force sensor. F=mA
- dicknuckle 7y ago
  I bet Louis Rossmann and other 3rd party apple repair services could figure it out.
  - rimlicker 7y ago
    they're probably just shorting the pvpvp3p33vp
    - BIKESHOPagency 7y ago
      ... v3 hot
      - deleted 7y ago
        [deleted]
exo762 7y ago
Talking about stretching terms - how about "zero knowledge" encryption marketed by cloud storage providers? Taking a cool sounding term from cryptography space and misapplying it to describe end to end encryption.
- s_fischer 7y ago
  They rely on people with "zero knowledge" of encryption to select them as vendors
cbm-vic-20 7y ago
I miss the days when reference manuals included code listings and schematics. https://archive.org/details/applerefjan78/ https://archive.org/details/applerefjan78/
- bigiain 7y ago
  As a maybe 13 or 14 year old, the manual for the Osbourne2 Z80 CPM machine dad bought contained enough information for me to work out how to connect a broken Atari video game joystick to the parallel port, and how to read it by peeking memory from Basic... Circuit diagrams, bank switched memory details, pretty sure someone dedicated could have built themselves their own machine with access to the manual and the right rom dump and system floppy disks...
electroguy 7y ago
“ It has to be some electro-magnetic based communication instead of currents so the circuit has to be more complicated. I doubt it's done without using any kind of software but would be glad to hear otherwise.” You can do the whole thing in analog fairly easily. The hardest part would be to get the magnetic sensor integrated into the same chip, but I guess that’s been a solved problem for a while.
Traster 7y ago
My suspicion is there's a hardware method of detecting lid closed - probably detecting a physical magnet (which is used anyway so that lid closes nicely) and that drives a transistor which then does the gating. I don't see why you assert that is has to be electro-magnetic based, as long as the gating is down by a 'dumb' fixed transistor rather than a programmable chip, then it's a hardware disconnect.
- est31 7y ago
  Interesting, it's magnet based. I've learned something today!
- lukifer 7y ago
  In the same spirit as putting tape over the webcam, I'd love it if someone found a solution for putting a tiny magnet in exactly the right spot to force-disable the microphone while the lid is open. :) I hope you're right, and I'd agree that would qualify as a "hardware disconnect". It's a little confusing given the mention of the T2 chip; they do differentiate some specific models which are "hardware alone", and at least imply that the T2 chip does not flip the off-switch on those. I'll have to go dig into iFixit's tear-downs to see if they found anything. For the 2020 iPad, they specifically mention "MFI compliant cases", so we can be fairly certain that one's done with magnets.
  - duskwuff 7y ago
    > I'd love it if someone found a solution for putting a tiny magnet in exactly the right spot to force-disable the microphone while the lid is open. :) It's the same sensor that's used to detect if the lid is open in general. Triggering it will prevent the display from turning on, and will make the computer go to sleep if it isn't running in "clamshell mode" (running on AC power with an external display attached).
    - lukifer 7y ago
      Disappointing, but makes sense, thanks for sharing.
blattimwind 7y ago
For analog, electret microphones a mute switch is very simple. Simply put an R-C pair (R a few MΩ, C 10-20 µF) in parallel to the microphone capsule. To mute it, short the R out. This is pop-free because the R charges the capacitor to the DC operating point of the capsule. When the R is shorted out, the microphone's output is shunted by the capacitor, which attenuates the signal level by >40-60 dB. For digital microphones it can also be very simple. Consider a PDM microphone, if you disconnect the data line and have it stick to either high or low through a pull-up, the signal becomes DC. This wouldn't be pop-free by itself, but it should be rather easy to make it so through DSP. (FWIW, you can also easily mute pro-audio microphones by shorting (+) and (-) together. The attenuation is determined by the output impedance of the microphone, usually a few hundred Ohms, divided by the resistance of your switch. Typically you'll get like 60 dB from this, which is perfectly fine for muting in a normal setup, but if you crank the preamp all the way up you can still get a usable, albeit very noisy, signal out of it.)
- markrages 7y ago
  Shorting the mic signal is not a straightforward solution. For one thing, you can just amplify your signal right back up to intelligibility, since 40-60dB attenuation doesn't go under the noise floor of a well-designed system. Just send the mic signal through an op-amp with an enable input.
  - blattimwind 7y ago
    Forward isolation is not necessarily much better than -60 dB depending on the exact op amp.
- deleted 7y ago
  [deleted]
detaro 7y ago
Considering firmware as part of the hardware from a higher-level view is not necessarily that weird in itself. It really depends on the details. I.e. a simple microcontroller with a program in ROM is also "firmware", but not all that different from a pure electronic ciruit. For more complex systems it becomes a more difficult question. Also, why would detecting a closed iPad sleeve require "electro-magnet based communication"? Seems like detecting presence of a magnet would be enough.
- gumby 7y ago
  As a former firmware developer (not for Apple, for power generation) it has firmware its not a hardware solution. We have automatic steam cutoffs that are entirely mechanical. I have built a state machine out of hardware logic that would have cost less than a dollar with a microprocessor but was preferred because it could be verified to work and not be remotely “upgradeable”.
  - lathiat 7y ago
    The computer free automation of a jukebox from the 1970s is an eye opener: (an in depth teardown and explanation) https://youtu.be/NmGaXEmfTIo https://youtu.be/NmGaXEmfTIo
foobarbecue 7y ago
There seems to be a new broad trend of stretching feature names. Shopping for headphones, "noise cancelling" began to be used recently to mean "pretty good seal" and now I see "7.1 Surround Sound" on headphones with two drivers to mean "has some fancy audio processing."
- gumby 7y ago
  It’s not new, sadly. The phrase “snake oil” goes back to the 19th century but names a phenomenon going back millennia.
  - dredmorbius 7y ago
    The original snake oil, from the Chinese water snake, (Enhydris chinensis), worked. Ingedients being hard to come by, and the market uninformed but spend-happy, hucksters appeared and the "medicine show‘ emerged. Patent medicines were also amongst the first widely advertised products in mass media beginning in the mid-19th century. https://www.collectorsweekly.com/articles/how-snake-oil-got-a-bad-rap/ https://www.collectorsweekly.com/articles/how-snake-oil-got-... http://gen.lib.rus.ec/scimag/?q=10.1007%2Fs12686-014-0200-1 http://gen.lib.rus.ec/scimag/?q=10.1007%2Fs12686-014-0200-1 http://www.npr.org/blogs/codeswitch/2013/08/26/215761377/a-history-of-snake-oil-salesmen http://www.npr.org/blogs/codeswitch/2013/08/26/215761377/a-h... http://umm.edu/health/medical/altmed/supplement/omega3-fatty-acids http://umm.edu/health/medical/altmed/supplement/omega3-fatty...
- hanniabu 7y ago
  I'm actually looking for headphones now. How would I know what headphones have actual noise canceling features?
  - chiefgeek 7y ago
    Try the Sony WHX line. Got a pair last fall and they are great.
  - etherealG 7y ago
    Look for details of the audio processing in the tech specs. Even better, check a good reputable review site like headfi.
marcan_42 7y ago
Most embedded microphones these days are digital MEMS microphones, using PDM. For those, if you gate off the digital signal, it's gone for good. I wouldn't be surprised if this is what Apple is doing. This is how the Google Home Mini does it. When you flip the mute switch, an AND gate kills the digital signal from both microphones (a stereo microphone pair share a single data line). All the audio hardware gets is a string of 0 bits at that point.
TheKarateKid 7y ago
I would still like to see Apple implement a Dell-style physical slider to close/block the webcam lens while the laptop is opened.

by est31 7y ago

jwr 7y ago

> I'd still love to see wiring diagrams or explanations how it actually works. Which kind of circuit do they use? I'd like to see that too, but I don't think we will. I suspect it's a magnetic switch and I'm also curious which lines it cuts. FWIW, you can still get some audio from an accelerometer if you can get it to report data with a high enough frequency. Not sure what you mean about iPhones, their information does not mention the iPhone (and I would not expect it to).

est31 7y ago
> Not sure what you mean about iPhones, their information does not mention the iPhone (and I would not expect it to). I meant iPads but got confused. Thanks for pointing it out.
derefr 7y ago
I’d think the raw pressure-level input from the force sensors on the trackpad would be even more accurate. It’s essentially an array of transducers already.
- markrages 7y ago
  An accelerometer on a physical object is a force sensor. F=mA
dicknuckle 7y ago
I bet Louis Rossmann and other 3rd party apple repair services could figure it out.
- rimlicker 7y ago
  they're probably just shorting the pvpvp3p33vp
  - BIKESHOPagency 7y ago
    ... v3 hot
    - deleted 7y ago
      [deleted]

exo762 7y ago

Talking about stretching terms - how about "zero knowledge" encryption marketed by cloud storage providers? Taking a cool sounding term from cryptography space and misapplying it to describe end to end encryption.

s_fischer 7y ago
They rely on people with "zero knowledge" of encryption to select them as vendors

cbm-vic-20 7y ago

I miss the days when reference manuals included code listings and schematics. https://archive.org/details/applerefjan78/ https://archive.org/details/applerefjan78/

bigiain 7y ago
As a maybe 13 or 14 year old, the manual for the Osbourne2 Z80 CPM machine dad bought contained enough information for me to work out how to connect a broken Atari video game joystick to the parallel port, and how to read it by peeking memory from Basic... Circuit diagrams, bank switched memory details, pretty sure someone dedicated could have built themselves their own machine with access to the manual and the right rom dump and system floppy disks...

electroguy 7y ago

“ It has to be some electro-magnetic based communication instead of currents so the circuit has to be more complicated. I doubt it's done without using any kind of software but would be glad to hear otherwise.” You can do the whole thing in analog fairly easily. The hardest part would be to get the magnetic sensor integrated into the same chip, but I guess that’s been a solved problem for a while.

Traster 7y ago

My suspicion is there's a hardware method of detecting lid closed - probably detecting a physical magnet (which is used anyway so that lid closes nicely) and that drives a transistor which then does the gating. I don't see why you assert that is has to be electro-magnetic based, as long as the gating is down by a 'dumb' fixed transistor rather than a programmable chip, then it's a hardware disconnect.

est31 7y ago
Interesting, it's magnet based. I've learned something today!
lukifer 7y ago
In the same spirit as putting tape over the webcam, I'd love it if someone found a solution for putting a tiny magnet in exactly the right spot to force-disable the microphone while the lid is open. :) I hope you're right, and I'd agree that would qualify as a "hardware disconnect". It's a little confusing given the mention of the T2 chip; they do differentiate some specific models which are "hardware alone", and at least imply that the T2 chip does not flip the off-switch on those. I'll have to go dig into iFixit's tear-downs to see if they found anything. For the 2020 iPad, they specifically mention "MFI compliant cases", so we can be fairly certain that one's done with magnets.
- duskwuff 7y ago
  > I'd love it if someone found a solution for putting a tiny magnet in exactly the right spot to force-disable the microphone while the lid is open. :) It's the same sensor that's used to detect if the lid is open in general. Triggering it will prevent the display from turning on, and will make the computer go to sleep if it isn't running in "clamshell mode" (running on AC power with an external display attached).
  - lukifer 7y ago
    Disappointing, but makes sense, thanks for sharing.

blattimwind 7y ago

For analog, electret microphones a mute switch is very simple. Simply put an R-C pair (R a few MΩ, C 10-20 µF) in parallel to the microphone capsule. To mute it, short the R out. This is pop-free because the R charges the capacitor to the DC operating point of the capsule. When the R is shorted out, the microphone's output is shunted by the capacitor, which attenuates the signal level by >40-60 dB. For digital microphones it can also be very simple. Consider a PDM microphone, if you disconnect the data line and have it stick to either high or low through a pull-up, the signal becomes DC. This wouldn't be pop-free by itself, but it should be rather easy to make it so through DSP. (FWIW, you can also easily mute pro-audio microphones by shorting (+) and (-) together. The attenuation is determined by the output impedance of the microphone, usually a few hundred Ohms, divided by the resistance of your switch. Typically you'll get like 60 dB from this, which is perfectly fine for muting in a normal setup, but if you crank the preamp all the way up you can still get a usable, albeit very noisy, signal out of it.)

markrages 7y ago
Shorting the mic signal is not a straightforward solution. For one thing, you can just amplify your signal right back up to intelligibility, since 40-60dB attenuation doesn't go under the noise floor of a well-designed system. Just send the mic signal through an op-amp with an enable input.
- blattimwind 7y ago
  Forward isolation is not necessarily much better than -60 dB depending on the exact op amp.
deleted 7y ago
[deleted]

detaro 7y ago

Considering firmware as part of the hardware from a higher-level view is not necessarily that weird in itself. It really depends on the details. I.e. a simple microcontroller with a program in ROM is also "firmware", but not all that different from a pure electronic ciruit. For more complex systems it becomes a more difficult question. Also, why would detecting a closed iPad sleeve require "electro-magnet based communication"? Seems like detecting presence of a magnet would be enough.

gumby 7y ago
As a former firmware developer (not for Apple, for power generation) it has firmware its not a hardware solution. We have automatic steam cutoffs that are entirely mechanical. I have built a state machine out of hardware logic that would have cost less than a dollar with a microprocessor but was preferred because it could be verified to work and not be remotely “upgradeable”.
- lathiat 7y ago
  The computer free automation of a jukebox from the 1970s is an eye opener: (an in depth teardown and explanation) https://youtu.be/NmGaXEmfTIo https://youtu.be/NmGaXEmfTIo

foobarbecue 7y ago

There seems to be a new broad trend of stretching feature names. Shopping for headphones, "noise cancelling" began to be used recently to mean "pretty good seal" and now I see "7.1 Surround Sound" on headphones with two drivers to mean "has some fancy audio processing."

gumby 7y ago
It’s not new, sadly. The phrase “snake oil” goes back to the 19th century but names a phenomenon going back millennia.
- dredmorbius 7y ago
  The original snake oil, from the Chinese water snake, (Enhydris chinensis), worked. Ingedients being hard to come by, and the market uninformed but spend-happy, hucksters appeared and the "medicine show‘ emerged. Patent medicines were also amongst the first widely advertised products in mass media beginning in the mid-19th century. https://www.collectorsweekly.com/articles/how-snake-oil-got-a-bad-rap/ https://www.collectorsweekly.com/articles/how-snake-oil-got-... http://gen.lib.rus.ec/scimag/?q=10.1007%2Fs12686-014-0200-1 http://gen.lib.rus.ec/scimag/?q=10.1007%2Fs12686-014-0200-1 http://www.npr.org/blogs/codeswitch/2013/08/26/215761377/a-history-of-snake-oil-salesmen http://www.npr.org/blogs/codeswitch/2013/08/26/215761377/a-h... http://umm.edu/health/medical/altmed/supplement/omega3-fatty-acids http://umm.edu/health/medical/altmed/supplement/omega3-fatty...
hanniabu 7y ago
I'm actually looking for headphones now. How would I know what headphones have actual noise canceling features?
- chiefgeek 7y ago
  Try the Sony WHX line. Got a pair last fall and they are great.
- etherealG 7y ago
  Look for details of the audio processing in the tech specs. Even better, check a good reputable review site like headfi.

marcan_42 7y ago

Most embedded microphones these days are digital MEMS microphones, using PDM. For those, if you gate off the digital signal, it's gone for good. I wouldn't be surprised if this is what Apple is doing. This is how the Google Home Mini does it. When you flip the mute switch, an AND gate kills the digital signal from both microphones (a stereo microphone pair share a single data line). All the audio hardware gets is a string of 0 bits at that point.

TheKarateKid 7y ago

I would still like to see Apple implement a Dell-style physical slider to close/block the webcam lens while the laptop is opened.