RS485 Frame Sensor

The rs485_frame sensor platform exposes hub-state diagnostics (frame counters, CRC failures, queue depth, etc.) as Home Assistant sensors. It requires the RS485 Frame hub to be configured.

User payload decoding is not done on this platform. To decode the contents of received frames, use on_frame: on the hub with platform: template sensors — that pattern handles every case from a single bit-field LED mask through a multi-field temperature/text frame.

Configuration variables

• rs485_frame_id (Required, ID): The ID of the rs485_frame hub.

• decode (Required, string): Which hub diagnostic value to publish. Each decode value carries Home-Assistant-conformant defaults (state class, unit, and for last_keepalive_ms a device class) so you do not have to set them yourself:

  decode	Description	state_class	unit_of_measurement	other
  frames_received	Validated frames received.	total_increasing	frames
  crc_failures	Frames that failed validation (CRC or structural).	total_increasing	frames
  commands_sent	User commands transmitted (idle keepalives excluded).	total_increasing	commands
  command_drops	Commands dropped (queue full or sniffer mode).	total_increasing	commands
  last_keepalive_ms	Gate-frame interval in ms.	measurement	ms	device_class: duration
  queue_depth	Current TX queue depth (including any pending delayed).	measurement	commands

All other options from Sensor. Every diagnostic also defaults to entity_category: diagnostic. You can override any of the per-decode defaults by setting the same key explicitly in YAML.

Sensors publish on change only. A counter that has not advanced does not generate API traffic, so no throttle filter is required for steady-state operation.

Example

sensor:
  - platform: rs485_frame
    rs485_frame_id: pool
    name: "Frames Received"
    decode: frames_received

  - platform: rs485_frame
    rs485_frame_id: pool
    name: "CRC Failures"
    decode: crc_failures

  - platform: rs485_frame
    rs485_frame_id: pool
    name: "Queue Depth"
    decode: queue_depth

Interpreting the counters

• A rising crc_failures with zero frames_received usually means the wrong baud rate or UART settings.
• A small steady crc_failures alongside healthy frames_received suggests crc.type or crc.rx_accept needs adjustment.
• command_drops should stay at 0 in normal operation. With queue_policy: replace_latest, every press that arrives while another command is pending increments the counter — useful for detecting button mash. With queue_policy: fifo, drops indicate the queue is too small.
• last_keepalive_ms shows the bus poll interval. Sudden changes here often indicate bus contention or controller reboots.