Complexity of emergency-only baseband firmware development

[Denver Gingerich]

Hi everyone,

I'm building some FOSS tools that let people send/receive calls/SMS without a cell plan (mainly using VoIP carriers that also offer SMS/MMS).  Eventually I would like to be able to bundle these tools with a phone that runs only free software.

In order to still provide standard emergency calling features (112/999/911 calling/SMS), the phone would require a free baseband (like FreeCalypso), but it would not need to offer any non-emergency phone features, since those would be handled by the aforementioned FOSS tools primarily on wifi.

My understanding from being on the list for a while is that the current baseband firmware works for some basic use cases on existing phones, but the end goal of FreeCalypso will require building a phone (or at least the main board of one).  Do the existing basic use cases include sending emergency texts or calls?  If not, would developing the remaining pieces needed to do so be substantially easier for an emergency-only use case than for a complete all-purpose use case?

I'm guessing that there are certain parts of FreeCalypso that would not be required for emergency-only operation (perhaps some of the SIM card communication, for example), but I haven't written baseband software before so I don't have a good sense of how large the differences would be.

So I'd be curious to know if the emergency-only use case is substantially easier to develop for, or if it's roughly the same complexity as developing for the all-purpose use case, or somewhere in between.

You may have seen a similar message to this one on a different list - I'm hoping to hear from multiple projects and apologize if that feels like duplication.  Thanks for reading!

Denver
http://soprani.ca/