Newer Garmin Nuvi GPS including the 205, 205w, 255, 255w, 265T, 265WT, 275T, 500, 550, 750, 760, 770, 780, 755t, 765t, 775t, 785t, 850, 880, 5000, etc. have a new selling point of Hotfix technology.
Garmin Hotfix enable the GPS to be super fast within seconds in locating the satellites during startup. In fact, my Garmin Nuvi 255w can even work as if staying connected to satellites for a few minutes, when it started up indoor in the middle of my house.
This is made possible by using predictive calculations of satellite positions, which enables the behaviour of GPS satellites to be modelled based on broadcast ephemeris readings for accurate prediction of satellite positions up to a few days ahead. A single broadcast ephemeris reading allows the accurate prediction of satellite orbits which are developed and refined every time new broadcast ephemeris is obtained.
Some people are guessing that the Hotfix feature is based on SiRF InstantFix inside the newer version of SiRFstarIII chipset. However, we've just found out that Nuvi 255w is using STMicro Cartesio application processor instead, so it is not SiRF InstantFix which plays the magic.
In fact, the Garmin Hotfix technology is powered by Rx Networks GPStream SAGPS chipset. The GPStream Self Assisted GPS (SAGPS) is a derivative of GPStream Predicted GPS (PGPS) technology. GPStream PGPS is a 3rd generation Assisted GPS (AGPS) solution addressing the limitations of 1st and 2nd generation products, which is made available to some handphone devices with AGPS feature.
Click here to read more about Rx Networks GPStream SAGPS technology.
For those who are interested to know where I got the information about Garmin Nuvi 255w is using STMicro Cartesio application processor and Rx Networks GPStream SAGPS technology, it is mentioned in Page 10 of September 2008 edition (Volume 11 Issue 9) of Telecom Trends newsletter.
Tuesday, August 25, 2009
Garmin Hotfix technology powered by Rx Networks GPStream SAGPS chipset
Monday, August 24, 2009
Cartesio chipset used in Garmin Nuvi 255w GPS
I've been wondering what kind of GPS chipset is inside my Garmin Nuvi 255w GPS. Some say it is the famous SiRFstarIII, some say it is the Taiwanese MTK chipset, but I find out that it is actually the STMicro Cartesio.
In fact, all the current Garmin Nuvi 2x5 series of GPS are using this Cartesio automotive-grade infotainment application processor with embeded GPS receiver. It features the System-on-Chip (SoC) technology which combines the host CPU and a high-performance 32-channel GPS correlator, and also a large set of peripherals and interfaces.
Here are some of the technical information about the STMicro Cartesio (code name STA2062):
- High performance ARM926 333-MHz CPU
- High performance 32-channel GPS correlator
- Bus/DDR frequency is 166 MHz
- 32 KB embedded ROM for boot
- 2 banks of 64 KB embedded SRAM
- 0.5 KB embedded SRAM for back-up
- 4 GB total linear address space
- Operating temperature range from -40 to 85 °C
My GPS usage experience shows that this STMicro Cartesio is performing pretty good.
Switch the Garmin Nuvi GPS to Simulator Mode and vice-versa
The Garmin Nuvi GPS will automatically prompt you an option to switch to Simulator Mode when it is not able to contact with the satellites. Simulator Mode allows you to use the functions of the GPS, such as planning for a route to destination, even when you are indoor and cannot get satellites signal. Simulator Mode is very useful when you want to demo the GPS functions to others.
You can manually set the GPS into Simulator Mode, even when the GPS is able to get ssatellites signal, by going to Tools > Settings > System > GPS Mode and select "GPS Off". The GPS signal strength indicator on the top-left corner of the screen will have a red cross when you are in Simulator Mode.
From the Simulator Mode, you can switch your GPS back to "Normal" mode and start acquiring satellites signal by going to the same setting place.
