We created a minimum Lora implementation based on the RFM95 and the ATtiny85. The sketch that sends only outgoing messages, including encryption, on fixed channel and fixed SF is about 3.5 KB so we have plenty of room for extra’s. We have created a mini-PCB that holds the RFM95 on one side and the ATtiny on the other side, including a programming header. The PCB has some flexibility in the routing so you can decide on various ways to hook up the processor to the Lora transceiver and to use the remaining inputs for sensors (using JP1, JP3 and JP4). The minimum interface to the RFM95, existing of MOSI, CLK and NSS is in place and cannot be changed.
The 6-pin programming header interfaces to the 6 pin header on the Sparkfun Tiny Programmer.
Size is 22 x 22 mm and 8 mm thickness (in which the header accounts for 3 mm, so without header it would be 5 mm).
The pitch of all components is such that it can be soldered by hand, if you are not too unsteady
With this board you can reach sub 1 uA sleep current, allowing it to operate for years on a small cell. We use it for our own non-critical applications with just a single input, like a door contact, but we plan to make it available for the wide world as well.
We haven’t decided on pricing yet. If you are interested (either with or without components), pls send a mail to email@example.com