Discussions about hardware, including the Notecard, Notecarrier, or custom designs.
Hi Can you please help me on the below. We are in the final decision state but GPS poor performance is stopping us. Need your quick help to clarify a few things.
Notecards under Test
- What is the typical GPS TTFF ( Time to first fix) in case of the above notecards ?
- Does either of the notecards store the GPS scan information in non volatile memory, so that the next subsequent reading after reboot has a shorter time ?
- Does either one of the Note cards use the A-GPS feature ?
Hi @SPQmax and welcome to the Blues Wireless community!
- TTFF is going to vary based on the type of antenna you are using and how good of a view of the sky it has. I assume you are using one of our Notecarriers? If so, which one are you testing with?
- All of our Notecards store satellite orbital information which allows for a “warm start”, if you will, when using the GPS capabilities in
periodic mode. This info is usually saved if power to the Notecard is cut, but we don’t recommend cutting power entirely to the Notecard as it may result in the modem shutting down in an uncontrolled fashion which could result in the loss of satellite info. The Notecard is designed as a low-power device, idling at ~8uA, so cutting power to it is not very beneficial and in fact can cause issues.
- We do not use A-GPS.
Thanks Rob for explanation.
- We using the notecard in our new product. Notecard is connected to a SOM and controlled from Linux. We are trying with Taoglas “AGGBP.SL.25A” antenna.
- Based on your #2 point, I understand that if we keep the notecard powered on all the time, then we will not loose the satellite tracking information and we will get Lat/ Long value within 10 to 30 secs. Can you please confirm this.
- Finally do you see any diff in GPS performance between Narrow band and wideband notecard modules.
First off, since you aren’t using one of our Notecarriers, please make sure your board is connecting to pins 20 and 22 (VACT_GPS_OUT, VACT_GPS_IN) on the M.2 connector. This connection is required to route the bias voltage to the center pin on the Notecard’s GPS U.FL connector.
Regarding your other questions:
- That antenna looks like a good choice
- Yes…but again there are other factors (active vs passive antenna, view of sky) that can impact performance. Ideal TTFF can be around 30-40 secs and less if the prior fix was < 4 hours ago.
- Not really. I tend to gravitate towards the WBXX models anyway if the deployment location is predictable since the wideband Cat-1 Notecards do generally connect a little more quickly to cell towers than the narrowband models (this is certainly the case if you’re connecting to NB-IoT).