Driver Matrix

Driver	Use it for	Best first doc
simulated	deterministic fake process I/O without hardware	Simulated And Loopback
loopback	fast %Q -> %I local sanity checks	Simulated And Loopback
gpio	local edge/device pin mapping	GPIO
analog, pwm, counter, can	analog values, PWM outputs, counters and CAN frames on a chip or Linux	Analog, PWM, Counters And CAN
ethercat	deterministic fieldbus I/O	EtherCAT
modbus-tcp	register-mapped external systems	Modbus TCP
mqtt	broker-backed event/message exchange	MQTT
multi-driver	one runtime using more than one driver family	Multi Driver

Selection rule

1. Start with loopback or simulated when you are still proving logic.
2. Move to gpio or ethercat for local hardware.
3. Move to modbus-tcp or mqtt for external-system integration.
4. Use multi-driver only after each individual driver validates cleanly by itself.