11 ms·

I wonder if the GPS sync is a one-time requirement, or if it does it periodically to ensure that the device isn't moved.

tumult 17y ago
GPS simulators exist, though they're expensive. I wonder how cheaply you could make a ghetto one yourself?
- deleted 17y ago
  [deleted]
- brk 17y ago
  Would probably be easier to just plug it into a small UPS. If you were driving, you could very easily transport it hundreds or even thousands of miles without ever worrying about power loss.
PStamatiou 17y ago
From what I can gather it is only during initial setup and it didn't bug me when I moved it afterwards.. but I have to imagine that if it's unplugged for some period of time (ie if you are traveling with it somewhere..) it will try to get another GPS lock before proceeding.
- bsgamble 17y ago
  Another friend had to use an external GPS antenna to get it to lock appropriately, so I'm not surprised that you had to put it by the window. I would say this is common in multi-tenant buildings, especially concrete ones.
tomkinstinch 17y ago
It would probably violate the TOS, but it seems like it would be pretty simple to circumvent the location restriction. Very few companies produce GPS chips. Most devices that include GPS capability do not bother to reinvent the wheel, but instead elect to integrate an existing GPS processing chip. GPS chips usually output various location sentences over standard RS232 (or I2C) a rate of around 1 Hz. It is unlikely that AT&T went through the trouble to design their own GPS processor into the Femtocell ASIC--it's likely connected but separate. So, if the GPS data line could be isolated, it would be well within the capability of a microcontroller to feed fake GPS NMEA sentences [1] to the Femtocell ASIC using that line. Maintaining an updated time field in the NMEA sentences might require a separate real-time clock chip, but the Femtocell may not even examine the time given by the GPS. A PIC microcontroller could cost less than $5, not including the cost of a compiler and hardware programmer. Program a microcontroller to output an artificial location, cut a trace, solder a few leads, and you could make a Femtocell think it is Topeka, even if it is connected to the Internet in Turin. [1] http://aprs.gids.nl/nmea/ http://aprs.gids.nl/nmea/
- PStamatiou 17y ago
  and this is why I love Hacker News

tumult 17y ago

GPS simulators exist, though they're expensive. I wonder how cheaply you could make a ghetto one yourself?

deleted 17y ago
[deleted]
brk 17y ago
Would probably be easier to just plug it into a small UPS. If you were driving, you could very easily transport it hundreds or even thousands of miles without ever worrying about power loss.

PStamatiou 17y ago

From what I can gather it is only during initial setup and it didn't bug me when I moved it afterwards.. but I have to imagine that if it's unplugged for some period of time (ie if you are traveling with it somewhere..) it will try to get another GPS lock before proceeding.

bsgamble 17y ago
Another friend had to use an external GPS antenna to get it to lock appropriately, so I'm not surprised that you had to put it by the window. I would say this is common in multi-tenant buildings, especially concrete ones.

tomkinstinch 17y ago

It would probably violate the TOS, but it seems like it would be pretty simple to circumvent the location restriction. Very few companies produce GPS chips. Most devices that include GPS capability do not bother to reinvent the wheel, but instead elect to integrate an existing GPS processing chip. GPS chips usually output various location sentences over standard RS232 (or I2C) a rate of around 1 Hz. It is unlikely that AT&T went through the trouble to design their own GPS processor into the Femtocell ASIC--it's likely connected but separate. So, if the GPS data line could be isolated, it would be well within the capability of a microcontroller to feed fake GPS NMEA sentences [1] to the Femtocell ASIC using that line. Maintaining an updated time field in the NMEA sentences might require a separate real-time clock chip, but the Femtocell may not even examine the time given by the GPS. A PIC microcontroller could cost less than $5, not including the cost of a compiler and hardware programmer. Program a microcontroller to output an artificial location, cut a trace, solder a few leads, and you could make a Femtocell think it is Topeka, even if it is connected to the Internet in Turin. [1] http://aprs.gids.nl/nmea/ http://aprs.gids.nl/nmea/

PStamatiou 17y ago
and this is why I love Hacker News