Modbus Sensor

The modbus_controller sensor platform creates a sensor from a modbus_controller component and requires Modbus Controller to be configured.

Configuration variables:

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

  • name (Required, string): The name of the sensor.

  • register_type (Required): type of the modbus register.
    • coil: coils are also called discrete outout. Coils are 1-bit registers (on/off values) that are used to control discrete outputs. Read and Write access

    • discrete_input: discrete input register (read only coil) are similar to coils but can only be read.

    • holding: Holding Registers - Holding registers are the most universal 16-bit register. Read and Write access

    • read: Read Input Registers - registers are 16-bit registers used for input, and may only be read

  • address: (Required, int): start address of the first register in a range

  • value_type: (Required): datatype of the mod_bus register data. The default data type for modbus is a 16 bit integer in big endian format (MSB first)
    • U_WORD (unsigned float from 1 register =16bit

    • S_WORD (signed float from one register)

    • U_DWORD (unsigned float from 2 registers = 32bit)

    • S_DWORD (unsigned float from 2 registers = 32bit)

    • U_DWORD_R (unsigend float from 2 registers low word first )

    • S_DWORD_R (sigend float from 2 registers low word first )

    • U_QWORD (unsigned float from 4 registers = 64bit

    • S_QWORD (signed float from 4 registers = 64bit

    • U_QWORD_R (unsigend float from 4 registers low word first )

    • S_QWORD_R (sigend float from 4 registers low word first )

  • bitmask: (Optional) some values are packed in a response. The bitmask can be used to extract a value from the response. For example, if the high byte value register 0x9013 contains the minute value of the current time. To only exctract this value use bitmask: 0xFF00. The result will be automatically right shifted by the number of 0 before the first 1 in the bitmask. For 0xFF00 (0b1111111100000000) the result is shifted 8 posistions. More than one sensor can use the same address/offset if the bitmask is different.

  • skip_updates: (Optional, int): By default all sensors of of a modbus_controller are updated together. For data points that don’t change very frequently updates can be skipped. A value of 5 would only update this sensor range in every 5th update cycle Note: The modbus_controller groups component by address ranges to reduce number of transactions. All compoents with the same address will be updated in one request. skip_updates applies for all components in the same range.

  • register_count: (Optional): only required for uncommon response encodings The number of registers this data point spans. Default is 1

  • force_new_range: (Optional, boolean): If possible sensors with sequential addresses are grouped together and requested in one range. Setting foce_new_range: true enforces the start of a new range at that address.

  • lambda (Optional, lambda): Lambda to be evaluated every update interval to get the new value of the sensor.

  • offset: (Optional, int): only required for uncommon response encodings

    offset from start address in bytes. If more than one register is read a modbus read registers command this value is used to find the start of this datapoint relative to start address. The component calculates the size of the range based on offset and size of the value type For coil or discrete input registers offset is the position of the coil/register because these registers encode 8 coils in one byte.

  • All other options from Sensor.

This example will send 2 modbus commands (device address 1 assumed)

0x1 0x4 0x31 0x0 0x0 0x02 x7f 0x37 ( read 2 registers starting at 0x3100)

0x1 0x3 0x90 0x1 0x0 0x1 0xf8 0xca ( read 1 holding resister from 0x9001 )

- platform: modbus_controller
  modbus_controller_id: traceran
  id: pv_input_voltage
  name: "PV array input voltage"
  address: 0x3100
  unit_of_measurement: "V" ## for any other unit the value is returned in minutes
  register_type: read
  value_type: U_WORD
  accuracy_decimals: 1
  filters:
    - multiply: 0.01

- platform: modbus_controller
  modbus_controller_id: traceran
  id: pv_input_current
  name: "PV array input current"
  address: 0x3101
  unit_of_measurement: "A" ## for any other unit the value is returned in minutes
  register_type: read
  value_type: U_WORD
  accuracy_decimals: 2
  filters:
    - multiply: 0.01

- platform: modbus_controller
  modbus_controller_id: traceran
  name: "Battery Capacity"
  id: battery_capacity
  register_type: holding
  address: 0x9001
  unit_of_measurement: "AH"
  value_type: U_WORD

The modbus sensor platform allows you use a lambda that gets called before data is published using lambdas.

This example logs the value as parsed and the raw modbus bytes received for this register range

# Example configuration entry
sensor:
  - platform: modbus_controller
      modbus_controller_id: epever
      id: battery_capacity
      address: 0x9001
      name: "Battery Capacity"
      register_type: holding
      value_type: U_WORD
      lambda: |-
        ESP_LOGI("","Lambda incoming value=%f - data array size is %d",x,data.size());
        ESP_LOGI("","Sensor properties: adress = 0x%X, offset = 0x%X value type=%d",item->start_address,item->offset,item->sensor_value_type);
        int i=0 ;
        for (auto val : data) {
          ESP_LOGI("","data[%d]=0x%02X (%d)",i++ ,data[i],data[i]);
        }
        return x ;

Parameters passed into the lambda

  • x (float): The parsed float value of the modbus data

  • data (std::vector<uint8_t): vector containing the complete raw modbus response bytes for this sensor

    note: because the response contains data for all registers in the same range you have to use data[item->offset] to get the first response byte for your sensor.

  • item (const pointer to a SensorItem derived object): The sensor object itself.

Possible return values for the lambda:

  • return <FLOATING_POINT_NUMBER>; the new value for the sensor.

  • return NAN; if the state should be considered invalid to indicate an error (advanced).

See Also