Location Library: just XM0110, or any SiRFstarIV?

The SiWi AirPrime XM0110 GPS Module is based on SiRFstarIV™ - which, AIUI, is quite a common chipset.

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Is the “Location library for Open AT” specifically “locked” to just the XM0110, or can it be used with any SiRFstarIV™-based solution :question:

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Hi Awneil,

Your notion is correct. “Location library for Open AT” can be used only with XM0110 and not with any SiRFstarIV™-based solution.


Thanks, but could you explain why not :question:

Is there a technical reason(s), or is it just a licensing issue?

Coz there are some hardware related dependency with respect to XM0110.


Could you be specific?

As in, the hardware pins of XM0110 are being configured.


It seems very short-sighted of you to make that an obstacle to using other SiRFstarIV-based designs!!

Surely, it is in your interest to make the library as widely applicable as possible?

It shouldn’t be hard to make things like hardware pin configuration separate from the “core” GPS functionality :question:

Hi Awneil,

I have double checked with the plug-in team and the news is that the library is compatible with the SiRF IV modules (but not for the SiRF III or SiRF V). It should work iff the user respects all hardware design specifications given in our documentations for the XM0110 when using another SiRF IV based solution (i.e. SiRF reset pin, ON_OFF management etc.).


Thats awesome! I assume it will only work with the SiRFstarIV GSD4t, and not the GSD4e which already has a built in processor? Or can it work with both?

The GSD4e is a standalone solution, so there is no need to use the OAT library for driving it (all the needed computations are done inside the GSD4e). A standard UART or I2C interface can be used for communicating with it and getting the NMEA frames, for example (which can be driven from a OAT application, for example). If nevertheless the GSD4e has to be used, the location library that is available now won’t be able to drive it.


Trouble is, NMEA gives only very limited control of the GPS module; to take advantage of advanced features - like power saving modes - you need the SiRF binary protocol.

It would be advantageous if SiWi would provide an SiRF binary protocol library or plug-in…

For reference, here’s the details of the 2 variants:

Before committing to using a SiRFstar IV solution I would recommend extensive testing under very bad conditions.

I can’t say much about it but with one SiRFstar IV solution under bad conditions we could get valid fixes that were hundreds of kilometers off from the correct position.
The manufacturer indicated that the problem was with SiRF firmware, but I have not heard anything about it for some time now.

I presume you mean that the solution claimed they were “valid” when they were, in fact, way off?

Do you recall if it was it possible to “qualify” this spurious “valid” indication against any other status(es) from the solution :question:

We have also seen this phenomenon where a valid 3D fix with low DOP values was actually many kilometres off. Unable to find any cause, or way to detect this, since the module indicates an excellent position.

Yes, the GPS claimed that the fix was valid.

There was no way of detecting this problem from the data itself (other than comparing against previous known good data).
DOP values and everything else indicated everything OK and good.
Plotting the data on a map shows that it even stays in the area of the incorrect position for a while before jumping back or jumping to a new incorrect position.

In our case the sequence was always like this:

Unit was going from area with good signal to area with bad signal
Fix was lost temporarily
Fix was restored
Fix was randomly after that way off
Proper position restored when signal was good again.

We have a temporary solution in place:
As soon as fix is lost, power off the GPS module and turn it on again.
Doing this clears any data that is used for fix in bad signal conditions and good signal conditions are necessary to restore fix again.
The downside of this is of course that it takes longer time to get a new fix if it is lost temporarily.

Using same antenna but SiRF III based GPS instead under the same conditions, fix was only lost and didn’t come back until signal was good again.

We had to convince the manufacturer to actually test and reproduce on their own before they escalated it further to SiRF/CSR.