[poll: vote now!1!!] 3G paranoia: Discussing solutions

Do you trust the 3G module? That is, if it claims it is off, do you believe it?

  • Yes (>99%)

    Votes: 56 43.4%
  • Probably (67%-99%)

    Votes: 40 31.0%
  • Don't know (33%-66%)

    Votes: 7 5.4%
  • Probably not (1%-32%)

    Votes: 13 10.1%
  • No (<1%)

    Votes: 13 10.1%

  • Total voters
    129

_jr_

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Well, I agree it is only a small difference, but it is still important to me. Just like I tend to check whether I actually have enough money in my pocket before going shopping even though in general my brain can be trusted to remember the actual amount accurately enough.
 

WizardStan

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I don't think that's comparable at all.

You want to talk money? Imagine there's a pickpocket. He's really really good, so good that he can steal money from your wallet while you're looking at it! Fortunately that's all he does, just takes the money out of your wallet and puts it back, leaving everything else alone. You're worried about your money being stolen so you invent a new type of wallet that turns on a bright light every time someone takes money out of it, that way, if the pickpocket happens to try to take money out of your wallet while you're searching for your drivers license (for example), the light will turn on and you'll be able to catch him in the act!

Of course, this also means the light'll go off every time you try to pay for something yourself. And the thief can always just take it while you're not actively looking at your wallet, but those are small prices to pay for the assurance that it won't happen while you're actually looking at your wallet at least.
 

_jr_

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Yes, I never did claim anything different. Still, this is a feature and believe it or not, it is valuable to me. I'm not demanding others feel the the same or that it gets put in, I'm just disagreeing with the claim that it is of no use whatsoever. I fully agree that it might not be useful to the majority of users and (if I try hard) I can imagine that it might actually be annoying to some of them and it is totally ok if it doesn't get implemented for this or other reasons, but I would be ever so slightly less happy (and can't help thinking that being annoyed by a LED is even more ridiculous). That's all I want to say and I feel compelled to repeat that as long as there are posts claiming that it adds absolutely nothing (very small positive number still being greater than zero). Sorry for that.
 

_wb_

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 (and can't help thinking that being annoyed by a LED is even more ridiculous)
Have you ever used a Pandora in total darkness? Besides the screen being too bright even at its lowest brightness setting, the LEDs can be very annoying. Luckily I can, and I do, switch them off.

A hardwired LED that is bright enough to be somewhat visible in daylight will be extremely annoying in total darkness.

And sure, a hardwired 3G LED is not completely useless. In the same sense that a hardwired display showing the current battery voltage and current draw is not completely useless, or making one of the keyboard buttons a hardwired instant hard reboot switch is not completely useless, or having a small e-ink display which is hardwired to show the current main screen display resolution is not completely useless. The point is that the usefulness is too small to justify the drawbacks.
 

_jr_

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I use the Pandora every day in total darkness for several hours (in part to read this board while lying in bed). The LEDs don't bother me even a little bit.


But I apologize for the remark, it wasn't neccessary. I agree, that the general usefulness might not be big enough for enough users to justify the implementation.
 

Askarus

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The Pyra is meant to be full user custoisable.

Only that one LED is not and you may not even turn it off!

I don't  ant to be forced to have that LED on!

I want to use it for something else.

Simply removing it leaves an useless and ugly LED hole somewhere.

Switch of Software but LED is trash.
 

Grench

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You could always put a little square of case colored electrical tape over the LED if it bothers you.
 

bubblebee

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I don't want to talk/ask further about the necessity of controlling the gsm chip. But could anybody (best from @hns) make a clear statement about the status quo about that ?
@hns talked in #12 about several possibilties about controlling the gsm chip:

  • the module has an internal FET power switch (to be controlled by an "ignite" GPIO and can be switched off by an AT command). This is required anyways.
  • we can add a series resistor and measure the voltage drop and convert that into a LED signal - this is the external power monitor. The level where the LED turns on should be ca. 30 mA.
  • a mechanical switch is critical - it must be reliable enough to carry 2-3 Amperes peak current (GSM pulses) if switched on.
  • An external electronic FET switch can be used instead.
So what measures to controll the gsm chip has found it's way to the current Pyra software and/or borard design ?

I have read the information at https://www.pyra-handheld.com/wiki/index.php?title=Modem :
"There's an CPU-GPIO controlled Hardware Switch(like an relay) to disconnect the whole Modem from Power so we don't have to rely on the Closed-Source Modem Firmware."​
Did that mean, that we actually have an "external electronic FET switch" ?

BTW: Yesterday I preordered my Pyra (standard edition, 4MB) without mobile chip, because I couldn't get enough satisfiable information about the previous questions/concerns.
 

levi

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I see no external switch on the case photos, but I assume based on comments thus far that you can use software to toggle power to it on and off. Similarly, if you try to talk to it using AT commands and it doesn't respond, and it doesn't seem to be taking excessive power, you can probably safely assume it's off.

FWIW: I preordered a Pyra with the GSM chip but I'm not planning yet to put a SIM in it. I bought it for the GPS and other bits and pieces on the same chip. I guess a hacker could still call the emergency services with it, and people with access to the masts could triangulate my location if the chip were switched on. Actually, I'd be interested to know if it were possible to power the GPS parts without powering the GSM bits, but I don't hold out much hope. Hopefully it will be possible to stop the GSM bit seeking masts while using the GPS circuits though.
 

hns

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1. there is internal power control of the WWAN modem module. It starts on an external "IGNITE" signal from some OMAP5 gpio and is turned off by an "AT^SMSO" command. This power switch is inside the modem module.
2. there is an external power FET switch (TPS22964CYZP) on the Pyra mainboard controlled through a gpio from the CPU. It can be turned on/off to cut power to the modem. So if you want to have it really off, do some "echo 0 >/sys/class/gpio/...".
3. there is an INA231YFF current sensor that can be queried ("cat /sys/class/hwmon/.../curr1_input") by the CPU and it measures the power consumption of the modem. I think the precision is in 1mA steps. But I have observed some offset (i.e. no current reported as -3mA or similar). Some simple daemon could use this information to turn on/off LEDs.

One thing to note: such 2/3/4G modems draw very little current while still active in reception mode. Some 3 mA (if base station is nearby) to 10 mA (if far away from a base station).
Otherwise, mobile phones could not reach standby times of up to 400 hours from small 1200mAh batteries and still be able to receive SMS and incoming calls to wake up the CPU.
 

levi

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Presumably these readings are averaged over some time interval. So it's still possible for a modem to consume 2A instantaneously but still only use a few mA over the course of a second, say. But there's perhaps enough capacitance floating around for you not to need to actually support 2A at any distance from the transistor in the chip, I don't really know.
 

bubblebee

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2. there is an external power FET switch (TPS22964CYZP) on the Pyra mainboard controlled through a gpio from the CPU. It can be turned on/off to cut power to the modem. So if you want to have it really off, do some "echo 0 >/sys/class/gpio/...".
This sounds excellent ! Trusting the Pyra and it's operating system we have full control over the modem chip.
I just have one more question: If I switch off the modem chip with the external power FET switch, all additional sensors and the GPS will also be switched off, won't they ?
 

lukey

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I just have one more question: If I switch off the modem chip with the external power FET switch, all additional sensors and the GPS will also be switched off, won't they ?
No, only GPS gets also switched off as it's Part of the Modem Module.
 

TrashyMG

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No, only GPS gets also switched off as it's Part of the Modem Module.
we don't know that for sure, the GPS despite being on the same module may be controlled independently. @hns could clarify this up.
 

hns

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we don't know that for sure, the GPS despite being on the same module may be controlled independently. @hns could clarify this up.
It shares the same power supply and signal processor as 2/3/4G inside the module. So it is also powered down for sure if you disable the power switch FET.
 
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