XM0110 Hot Start

I’m using location library 1.3 and trying to do a hot start. If I put the modem into sleep mode and power off the modem for less than one minute, then restore power and issue a hot start, the time to first fix is still between 30 and 60 seconds. According to the documentation I believe it should be less than 5 seconds. Has anyone else tried the hot start and had success? It appears the GPS will only ever warm start.

Which sleep mode are you using? I seem to remember that one of them (IDLE or HIBERNATE) doesn’t save ephemeris data to non-volatile memory, so power cycling the module causes it to lose the ephemeris. Try issuing a stop command before powering down.

I think powering down causes the module to lose its time, which it then has to update from GPS. If you want a hot start but with low power consumption, have a look at the deep sleep mode. Generally I just put the module into IDLE mode and leave it there, then your start times are 2-5 seconds.

Thanks for the response. I believe you’re correct about the time and date. There is no battery support for the real time clock on the XM0110 module. The idle mode seems to work well, but only if you keep power to the modem itself (I’m using an FXT009). This is an in vehicle application so I’m going to try and use an ignition input and put the FXT009 to sleep as well as the XM0110 into idle mode. My concern about putting the FXT009 to sleep is that the modem may crash and never recover. If that occurs, it’s a huge deal to get the modem power cycled.