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ESPHome - Smart Home Made Simple

Modbus Component

The Modbus protocol is used by many consumer and industrial devices for communication. This component allows components in ESPHome to communicate to those devices via RTU protocol. You can access the coils, inputs, holding, read registers from your devices as sensors, switches, selects, numbers or various other ESPHome components and present them to your favorite Home Automation system. You can even write them as binary or float ouptputs from ESPHome.

The various sub-components implement some of the Modbus functions below (depending on their required functionality):

Function CodeDescription
1Read Coil Status
2Read Discrete input Status
3Read Holding Registers
4Read Input Registers
5Write Single Coil
6Write Single Register
15Write Multiple Coils
16Write Multiple Registers

Modbus RTU requires a UART Bus to communicate.

# Example configuration entry
uart:
  ...


modbus:

Configuration variables

Section titled “Configuration variables”

  • id (Optional, ID): Manually specify the ID used for code generation.

  • uart_id (Optional, ID): Manually specify the ID of the UART Component if you want to use multiple UART buses.

  • flow_control_pin (Optional, Pin): The pin used to switch flow control. This is useful for RS485 transceivers that do not have automatic flow control switching, like the common MAX485. If your UART supports flow_control_pin, you should configure this in the uart component, not in the modbus component.

  • send_wait_time (Optional, Time): Time in milliseconds before the next ModBUS command is sent when an answer from a previous command has not yet started (i.e. when to timeout and assume no response is coming). Defaults to 250 ms. Set this value to the maximum time required for the slowest device on the bus to begin responding (time to first byte). If a device starts responding within this time, the next command will be queued and sent after the response is finished, no matter how long the response.

  • turnaround_time (Optional, Time): Time in milliseconds before the next ModBUS command is sent after last response is received. This interval allows other devices on the bus time to process messages. Defaults to 100 ms. This value is ideally set to the maximum time required for the slowest device on the bus to process a message and be ready to process another. Note that all devices will receive all messages and will require time to process them even if they don’t need to reply. If devices don’t respond sometimes, it can help to increase this value.

  • disable_crc (Optional, boolean): If set to true, invalid CRC values are ignored. This will reduce error messages but will not fix communication issues. Try increasing times above first if you see CRC errors. Defaults to false.

  • role (Optional, string): The role of this component, client or server. Defaults to client.

See Also

Section titled “See Also”