Old machines often already expose useful signals
The interface might be serial, RS-485, Modbus RTU/TCP, CAN-adjacent data, BLE, Ethernet, relay outputs, logs, CSV exports, or a local vendor application. The first job is discovery: what can be read safely and how reliable is it?
A gateway makes the data operational
A Raspberry Pi or embedded Linux gateway can read the device, buffer locally, publish MQTT, call an API, write a database, and expose diagnostics. The business value is machine visibility, uptime reporting, failure history, and fewer blind manual checks.
Undocumented protocols need a small investigation first
When the protocol is unclear, start with captures, logs, assumptions, and a go/no-go point. That protects the budget before promising a full integration.