ritiikaagupta/RoadSOS ? reverse-engineered prompt

Build me a prototype for RoadSoS, the emergency communication system for vehicles, focused on the FPGA part first.

I want an FPGA based LoRa baseband on a Spartan 7 with SystemVerilog, plus the supporting Python and testbench code needed to simulate and verify it. The goal is to make a simple emergency message path that can send a short SOS packet reliably over a vehicle to vehicle style radio link, with clear fallback friendly behavior for low signal situations. Please include the main transmit and receive logic, packet framing, basic error handling, and a clean way to test it in simulation.

Also add any setup notes, constraints, and a short explanation of how to run the simulations and synthesize it in Vivado. If you need to check current LoRa or Vivado details online, go ahead and do that. Keep it practical and readable, like something a team could continue building into the full multi tier RoadSoS system later.