The cool thing about cellular connectivity is you can use it just about anywhere in the world. The FONA GSM module can be used anywhere that 2G GSM exists. In the USA this is provided by T-Mobile so if you have T-Mobile coverage, you have GSM.
We provide cellular connectivity via the SIM800H module. This module uses AT commands and the main processor, the ATmega32u4, communicates via a UART connection. The AT commands are somewhat standard and they are all documented pretty well, but if you want to do something special that isn't already written up in our library, it can be a little bit of an adventure.
- Compared to WiFi, cellular requires much more power, and has lower data transfer rate. SSL support is not very clearly documented
- Compared to BTLE, data rate is about the same, but power requirement is waaaay higher
- Compared to LoRa or Packet radio, the data rate is about the same, but the power requirements are much higher. That said, you don't need to create your own radio network, you can just use the cellular net that already exists. There's no inherent range limitation, as long as GSM coverage is present.
Often times, the only real alternatives to cellular are WiFi or LoRa. WiFi is a good alternative - but only if you can be sure that there's a WiFi base-station or hotspot nearby. LoRa can do long range communication, up to a few KM but you need to set up your own network/gateway.
This section is fairly short because there's only one cellular-capable Feather at this time, the 32u4 FONA
- Can use (just about) anywhere in the world!
- Surprisingly low cost of entry
- Gain access to SMS network, phone calls, and Internet through GPRS
- Basic geo-location capability built-in via cell-tower triangulation (not as good as GPS but good to within ~1 mile)
- No need for a base-station or hotspot
- ATmega32u4 is well supported chip, with native USB and full Arduino core.
- You'll pay per message, call, text or megabyte. A SIM card and plan is required
- GSM is only supported by T-Mobile in the USA, and GSM will be supported until at least 2020 but after that, you'll want to upgrade to LTE
- High power requirements, a large battery is required to handle the 2 Amp power spikes when transmitting/connecting to the network
- Cellular connectivity can be spotty, especially when roaming. Code needs to be able to manage re-connection.
- AT commands can be a little clunky, require care and parsing.
- Extra large Feather to make space for the module
- Antenna placement often trips people up: if it's too close to the main processor it can reset the Feather, so you can't make it too compact.
- Cellular module runs directly off of LiPo battery so you cannot use only USB power