Source code for SX1308 is released at https://github.com/Lora-net /PicoGW...
To make a ultra low cost, yet complete 8-channel gateway.
SX1308 is basically a SX1301 with new commands to limit the power and be able to design a USB powered gateway.
The PicoGW platform uses a STM32 MCU running the lora-gateway-HAL and using USB-CDC interface (virtual com port) to connect to the (linux) host.
USB support was removed in the lora-gateway project because of the delays or latencies at SPI level using the FTDI SPI-to-USB translator. Now the use of USB happen at higher layer, delays are less critical.