Rick's b.log - entry 2010/09/12

GPS

I found a copy of the default manufacturer's software online. It is basic, but suffices for testing purposes.

It now makes sense. You see, the GPS satellites are always moving. When a GPS unit first starts up, it must lock into a satellite (they, uh, all use the same frequency!) and retrieve something called the almanac. This describes the orbits of the satellites. With this, a three-dimensional idea of the placement of each satellite can be created. Now, for all of the satellites "in view", the signal can be received and locked in. The GPS, as far as I'm aware, just broadcasts its idea of time (to, like, nanoseconds accuracy) as well as ident and almanac data. The receiver then uses miniscule timing differences in the received signals to calculate how far away each satellite is. And knowing its orbital position and distance, it will permit the current location to be determined. At least four satellites are required to fix a position, and the more that are picked up (the receiver claims to be able to lock into 16, but in reality any location will 'see' between 8 and 12 at any given time) the more accurate the information returned. It is able to put a precise fix on my house fairly easily, but with fewer satellites, the altitude varies randomly. And with only four satellites, you might find you suddenly start moving standing still. This is, no doubt, a side effect to the rotation of the earth and the orbits of the satellites. You are standing still, but those birds perform two rotations per sidereal day. Complicated? It's a wonder it works at all, never mind a domestic unit in my hand (costing me all of three euros!) that can give not only my location but also report on my heading and current speed.

Talking to my computer, it uses a virtual serial port to report information such as this, once per second:

  $GPGGA,000000.000,0000.0000,S,00000.0000,W,0,00,00.0,0.0,M,0.0,M,,*52
  $GPGSA,A,1,,,,,,,,,,,,,0.0,0.0,0.0*30
  $GPRMC,000000.000,V,0000.0000,S,00000.0000,W,0.00,0.00,210724,,,A*74
  $GPVTG,0.00,T,,,0.00,N,0.00,K,A*70

WAG200G

Anyway, back to today. Back to the router. The Livebox is not only a pig to get into (programmatically), it is also pretty useless at providing information. I can tell you:

  Atténuation Up (dB) :                      21,4 dB
  Atténuation Down (dB) :                    50,0 dB
  Signal bruit Up (dB) :                      2,0 dB
  Signal bruit Down (dB) :                    5,0 dB
  Débit maximum possible ligne Up (kb/s) :    952 kb/s
  Débit maximum possible ligne Down (kb/s) : 3400 kb/s
  Puissance émise (dBm) :                    12,5 dBm
  Puissance reçue (dBm) :                    17,6 dBm

But history? Nope. Ability to telnet in to retrieve stats? Nope. Report on actual line quality? Nope.

I couldn't use the WAG all the time, it does not support the VoIP telephony required by our phone line.

Anyway. I got my user name and password, set up the parameters to a way that should be correct (PPPoA, VC, 8/35, pretty much everything else on auto). But no connect. I am wondering if it might be a problem with the ADSL hardware?

The router runs a form of Linux. I updated it to the latest official firmware, then went a step further to OpenWAG which gives geek access (SCP, telnet, etc). I wonder if there is some sort of way to test the ADSL device, maybe a loopback test or somesuch, which might tell me if the main IC is okay.

Never dabbled much in stuff like this, here's the phone line input circuitry:

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