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

Modbus RTU requires a UART Bus to communicate.

# Example configuration entry
uart:
  ...

modbus:

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 support flow_control_pin you should preferentially set it in the uart component over the mobus 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 2000 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 (i.e. how long to allow all devices to process messages on the bus). Defaults to 600 ms. Set this value 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 hear all messages, so will need to process them even if they don’t need to reply. If devices don’t respond sometimes, it can help to increase this value.
role (Optional, string): The role of this component, client or server. Defaults to client.