The ISM420 and ISM480 require 1.8V to run. The I/O inputs are 3.3v tolerant, however the I/O output is only at 1.8v. If you micor does not support 1.8V you will need a translator chip.
How do you connect to the ISM480?
The ISM480 has an Ipex 12 pin connector header and you need to put the same mating connector on your board and connect via a flex ribbon cable. Inventek supplies a two length ribbon cables and the Ipex connectors on the website shop to make user integration easy.
Can the GPS be flashed in System?
Yes, the ISM300x and the ISM480x family of GPS can be flashed in system. You need to control the flash enable pin and you can upgrade teh flash through the UART.
What information is available to indicate the degree of accuracy of the GPS data at any given time?
What information is available to indicate the degree of accuracy of the GPS data at any given time? What is the criteria used to establish HDOP, is it only related to satellite location and signal strength?
We provide HDOP and EHPE in MID 41 as an indication of position accuracy. HDOP is computed only from satellite geometry – azimuth and elevation and number of satellites – there is no signal strength factor (attached DOP formula). See attached document on position error for a better understanding
What does the GPS firmware do with the acceleration / speed at high altitude build for us to 135k feet?
The high-altitude change was simply setting the upper limits on a solution from the Kalman filter. It had no effect on how we report altitude or speed or how we handle acceleration. Therefore, with such a build we still make the same determinations we do in unmodified software: before we report a location the two conditions of the ITAR limits must be verified.
Limit 1: speed cannot be above 1000 kts (514 m/s) when altitude is above 60,000 feet (18288 m) – both conditions must be met at the same time for this to cause position output to stop.
Limit 2: speed cannot exceed 600 m/s regardless of altitude. Since velocities of winds aloft are never expected to reach 1000 kts, the high-altitude build should work just fine for things that are drifting in the atmosphere like weather balloons. However, sounding rockets and the likes do not work as they exceed those limits.
How do I choose the best GPS for my application?
The newest GPS technology we have today is the SiRF IV GPS modules and we offer two products, the ISM420 and the ISM480. The ISM420 is a ROM based solution with no antenna attached, while the ISM480 is a Flash based solution with antenna attached. Ideally, one of these two GPS will fit your need.
If you are looking for custom firmware for a specific application we may suggest the Sirf III based modules for example high altitiude ballons for example, you will use the ISM300F2-C5.1-VOO4 which is designed specifically for high altitude.
Also, if you are looking for a GPS that is easy to solder down and has the ability to snap on various external antenna’s I would choice the Sirf III based ISM300F2-C4.1 that has a connector on top of the module or you can run on your board via a 50 ohm trace.