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name: ha-modbus-integration description: Patterns for building Home Assistant custom integrations that talk Modbus (TCP/RTU-over-TCP/serial): pymodbus device_id usage, safe polling/writing, pacing/backoff, encoding multi-register values, cached fallback, and translation-backed entities. license: Complete terms in LICENSE.txt

HA Modbus Integration

Use this when implementing or refactoring HA custom components that communicate with Modbus devices.

Quick start

• Pick connection mode (tcp, rtuovertcp, serial); set timeout and message spacing.
• Always pass the correct unit id (device_id/slave) on every read/write.
• Batch contiguous reads, lock IO, and tier polling; cache last good data for availability.
• Encode multi-register writes (float32/uint32) and avoid immediate post-write refresh.
• Use translation_key + entity.sensor names and stable unique/device ids.

References

• references/connection-modes.md
• references/read-write-patterns.md
• references/resilience-and-pacing.md
• references/translations-and-ids.md