Improving ColdStart Aquisition Times

[askpatrickw]

I did a little research on this... the main thing seems to be if you had a reliable clock (RTC) and a known last good position. You could use PMTK 740 and PMTK 741 to inject time and position and improve the cold start performance.

I don't think your library can do this magically for the user, but it might be something the user could do when initializing L76GNSS if they had a battery powered RTC and a reliably cached last position. I'm not sure of the impact of loading a bad time or position.

Maybe not enough to start coding from, but good information to save here for future reference.

Helpful Quectel Information:

• Potential Hardware Board esign Issue
• With helper Location and Time you can Improve Cold_Start times using PMTK 740 and PMTK 741

PMTK_DT_UTC

Packet Type: 740
Format: $PMTK740,YYYY,MM,DD,hh,mm,ss*CS<CR><LF>
Example: $PMTK740,2010,2,10,9,0,58*05<CR><LF>
The packet indicates that the current UTC time is 2010/Feb/10 09:00:58.

PMTK_DT_ POS

Packet Type: 741
Format: $PMTK741,Lat,Long,Alt,YYYY,MM,DD,hh,mm,ss *CS<CR><LF>
Example: $PMTK741,24.772816,121.022636,160,2011,8,1,08,00,00
The packet indicates that the GNSS receiver is at:

• latitude 24.772816 degrees
• longitude 121.022636 degrees
• altitude 160 meters

[andrethemac]

Hi Patrick.
First sorry for the late answer. Other work is eating my time.
If I'm not mistaken, the lopy/wipy/... cut's the power to the pytrack board when it goes to sleep. The gps always wakes in a cold state. I have some rtc boards with a battery. But haven't had the time to add them to the board. No extra headers on the board makes it difficult to add extra hardware (and I've a lousy soldertechnique).
It's on my list.
André

[convertl]

Hello,
For your information I implemented PMTK740/741 functions on the library to accelerate cold start. I get time and approximate location from the Internet (with a Fipy). It accelerates the cold start effectively.
I will try to commit my changes in near future.

I also implemented host EPO download but it is very long and most of the time I get the fix before finishing to upload the EPO data.