These are the datasheets for the cell module on the FONA 3G.
- SIM5320 AT Command set manual
- SIM5320 Hardware Design
- SIM5320 Specification
- GPRS / TCP/IP App note
- SIM5320 USB drivers (We tried this on windows sucessfully, also looks like there's some sort of linux drivers)
- EagleCAD PCB Files on GitHub
- Fritzing object in the Adafruit Fritzing Library