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 Code



Read Coil Status


Read Discrete input Status


Read Holding Registers


Read Input Registers


Write Single Coil


Write Single Register


Write Multiple Coils


Write Multiple Registers

Modbus RTU requires a UART Bus to communicate.

# Example configuration entry


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.

  • send_wait_time (Optional, Time): Time in milliseconds before the next ModBUS command is sent if an answer from a previous command is pending. Defaults to 250 ms. If multiple ModBUS devices are attached to the same bus increasing this value can help avoiding to to overlapping reads. When two devices are sending a command at the same time the response read from UART can’t be assigned to the proper design. This value defines the maximum queuing time for a command before it is send anyways.

  • disable_crc (Optional, boolean): Ignores a bad CRC if set to true. Defaults to false

See Also