Raspberry Pi Battery Swap Gateway

I’m replacing a bulky PLC in my six-slot battery-swapping station with a Raspberry Pi (or any reliable Linux SBC) and need end-to-end gateway firmware written in Python or Node.js. Core functions I must see working • MQTT link: publish live slot and battery data to my cloud server and accept commands from the same endpoint plus our mobile app. • Lock control: drive a 12 V relay board that energises the electromagnetic locks on all six slots. A cloud “unlock” or “lock” command should actuate the relay instantly. • Dual-bus BMS reading: collect SoC, voltage, temperature and any fault flags from the batteries over both CAN-Bus (MCP2515) and RS-485 Modbus, then forward the parsed payload upstream. • Connection-loss rule: if the Pi loses Internet, every slot must stay locked until connectivity is restored—no local fall-backs. I’ll provide API details, topic structure and sample payloads; you bring the hardware expertise, especially if you have prior EV telematics or BMS integration under your belt. Delhi-NCR presence is handy for occasional on-site tests, yet remote work is fine as long as you can bench-test with your own Pi, relay module and CAN/RS485 adapters. Deliverables 1. Clean, commented source (Git repo) with setup scripts. 2. Wiring diagram and bill of materials for repeatable builds. 3. Test video or live session showing: a) successful CAN and RS-485 reads, b) cloud-initiated lock/unlock, and c) enforced lockout during simulated network drop. 4. Quick-start guide so my technicians can flash and deploy the image in our enclosure. I’m ready to start as soon as you confirm you have the hardware to replicate the scenario. Budget: INR 12500–37500