-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi folks -
Spent the afternoon meddling with GPS about this highly variable behaviours it has, but I am not sure it did anything useful. I never see the bad behaviours with an external GPS antenna connected, only with internal antenna. If you connect an external antenna to the internal antenna connector using the internal antenna cable, then it also works fine. Since it seems the firmware can act differently depending on signal quality, and it seems it can illegally remember things from previous sessions even when the power is cycled, it's hard to tell from which direction any change in behaviour comes from. For example if things got better, is it because of the last change or because it has simply randomly incrementally reached a critical point with gathering data from the satellites? I decided to look at the internal antenna and took apart an internal antenna by removing its can, I noticed the phantom voltage on there used to power the internal LNA was a bit low at 2.63V. I decided to try to increase this, which I did by changing the level on LDO5, initially trying for 3.6V. But LDO5 can only generate something below 3.3V since its input is IO_3V3. When set to 3.2-ish, we get 2.85V on the internal antenna power. Unfortunately the GPS behaviour can be so sticky and variable that I didn't manage to make a test that pinned this down as having been effective. However I put this patch on andy branch and maybe it's worth a try by anyone with internal antenna GPS issues. By default this patch sets the GPS voltage to ~>3.2V instead of 3.0V. Another thing I tried was sending a UBX command CFG_RST each powerup to clear the battery backed up memory region of all its data, but this did not seem to do anything about the seemingly sticky behaviours between sessions. - -Andy -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org iEYEARECAAYFAkh6LbwACgkQOjLpvpq7dMrHEQCfUuOOF0AuQcmb7IAnv7M4cgsW HlkAnjsQZm/x5lPhDrd28IeBPIMeEcKO =TfFx -----END PGP SIGNATURE-----
