Arduino Clock: Getting The Time from Thin Air? Answered
I have made a few arduino based clocks now & one thing I been considering making an generic version of an atomic clock that can program itself with the local time using local GSM Network.
The idea came when I noticed that an old tmobile phone I had from years ago synced time & date automatically without an account or phone number assigned to it, as soon as a dropped the new sim card in the phone seemed to do an update of some type.
As I looked more into this, I noticed the phones wap (data) settings were no longer set to tmobile.wap, but was now programmed for at&t.wap.3g.net , that along with a few other network settings had been updated during a handshake!
This actually caught me off guard, I had always assumed that a data connection was required to request the time but this is not the case, the network does broadcast the time to all clients (even suspended accounts) during handshake, now if you want to use an AT-COMMAND to request the time, that requires data from what I understand.
Does anyone have experience using GSM & Arduino ? Is the handshake something that could be easlily "exploited" so to speak to get the time from thin air?
Any ideas would be appreciated...