These EmonTx and NanodeRF code guides go through the main components required to put a full EmonTx and NanodeRF (or ENC28J60 based OpenKontrolGateway) firmware together.
If your just starting out, you might find going through these guide examples first better than starting straight in with the fully fledged firmware examples.
The examples are contained in the normal emonTxFirmware and NanodeRF repositories on github.