TI Calypso chipset for GSM/2G

At the core of every GSM/2G handset or modem there is a specialized chip or a tightly-coupled set of chips (chipset for short) that is made specifically for GSM, implementing the mobile side of GSM air interface and other common functions typically required in a standard phone handset. During the years when GSM/2G was a mainstream technology, before it transitioned to being a retrotechnology in the sole care of people like us, many different core chipsets were produced for it by several different chip companies. Out of all historical GSM chipset vendors, one stands out and holds a special place for us: Texas Instruments.

Once upon a time, in a distant era long gone by, TI were in the business of making GSM (2G) and UMTS (3G) cellular baseband chipsets and the software that goes with them — but then they fully exited this business in 2009, and have since destroyed every trace of ever having been in it. All of the intellectual property associated with this business went into the trash dumpster — as we understand it, TI tried to sell that business unit, but failed to find an interested buyer.

During the years when TI were active in that business, they had produced many different chipset generations. The one TI GSM chipset that holds special significance to us is the one that was named Calypso, in addition to the more official but hard to pronounce name HERCROM400G2. The first version of Calypso silicon dates from around 2000; the final polished version of this chipset, the one we work with, dates from around 2004, and this final Calypso version was used in some mass-produced phone models from around 2004 till around 2007.

What makes this Calypso chipset so special

Back when it was current technology, TI Calypso chipset was nothing special, not standing out in any particular way from numerous others that came both before and after it. However, in the present time this chipset is very special because of certain historical developments that happened with it:

1. Some time between 2006 and 2010 this chipset attracted significant attention in the hacker community as a result of having been used as the GSM modem block in the legendary Openmoko smartphones that had their moment in the sun in those years.

2. Prompted by this community attention, significant hardware documentation for this chipset was found freely on the Internet, including detailed datasheets for every chip and full schematics for TI's Leonardo reference board.

3. Firmware liberation took longer, but was also achieved in 2013: in the Northern hemisphere fall of that year, the complete semi-src deliverable package (half source, half linkable binary objects) for TI's reference firmware for the Calypso chipset became free to the world.

4. The final key development was us, FreeCalypso, coming onto the scene: we have collected all of the disparate and incomplete source and documentation leaks, we have pieced them together into a complete and working whole, and we now act as de facto owners and custodians of this chipset.

What we offer in FreeCalypso

• FreeCalypso Tango is our core module that encapsulates our beloved Calypso chipset and the necessary RF components (all 4 GSM frequency bands) into a 41.2x36.0 mm package — this module is meant to be integrated as a component into other people's higher-level system designs such as Linux smartphones.

• We have two development boards: FCDEV3B and Caramel2.

• AT-command-controlled slave modems are not the only kind of products that can be built with our Calypso chipset. The other possible kind of Calypso product is a handset, also known as a dumbphone, a fully self-contained handheld device in which the Calypso serves as the main and sole processor, performing not only GSM modem functions, but also presenting the dumbphone UI and fully controlling the phone. See this page regarding our handset ideas.

• We maintain the full software suite for Calypso, consisting of the firmware that runs on the Calypso chip itself plus a large assortment of host-based development tools.