Modbus Controller¶

The modbus_controller component creates a RS485 connection to control a ModBUS slave device, letting your ESPHome node to act as a ModBUS master. You can access the coils and registers from your slave ModBUS device as sensors, switches or various other ESPHome components and present them to your favorite Home Automation system.

The modbus_controller component relies on the Modbus Component.

Hardware setup¶

You need an RS485 transceiver module:

See How is this RS485 module working? on stackexchange for more details.

The transceiver connects to the UART of the MCU. For ESP32, pin 16 to TXD and pin 17 to RXD are the default ones but any other pins can be used as well. 3.3V to VCC and naturally GND to GND.

On the bus side, you need 120 Ohm termination resistors at the ends of the bus cable as per ModBUS standard. Some transceivers have this already solderes onboard, and some slave devices may have them preinstalled with a jumper or a dip switch.

Note

If you are using an ESP8266, serial logging may cause problems reading from UART. For best results, hardware serial is recommended. Software serial may not be able to read all received data if other components spend a lot of time in the loop().

For hardware serial only a limited set of pins can be used. Either tx_pin: GPIO1 and rx_pin: GPIO3 or tx_pin: GPIO15 and rx_pin: GPIO13.

The disadvantage of using the hardware uart is that you can’t use serial logging because the serial logs would be sent to the ModBUS device and cause errors.

Serial logging can be disabled by setting baud_rate: 0.

See Logger Component for more details

logger:
    level: <level>
    baud_rate: 0

Configuration variables:¶

modbus_id (Optional, ID): Manually specify the ID of the modbus hub.
address (Required, ID): The ModBUS address of the slave device
command_throttle (Optional, Time): minimum time in between 2 requests to the device. Default is 0ms. Some ModBUS slave devices limit the rate of requests from the master, the interval between sending requests can be altered.
update_interval (Optional, Time): The interval that the sensors should be checked. Defaults to 60 seconds.
offline_skip_updates (Optional, integer): When a slave doesn’t respond to a command, it is marked as offline, you can specify how many updates will be skipped while it is offline. If using a bus with multiple slaves, this avoids waiting for timeouts allowing to read other slaves in the same bus. When the slave responds to a command, it’ll be marked online again.

Example¶

The following code creates a modbus_controller hub talking to a ModBUS device at address 1 with 115200 bps

ModBUS sensors can be directly defined (inline) under the modbus_controller hub or as standalone components Technically there is no difference between the “inline” and the standard definitions approach.

uart:
  id: mod_bus
  tx_pin: 17
  rx_pin: 16
  baud_rate: 115200
  stop_bits: 1

modbus:
  flow_control_pin: 5
  id: modbus1

modbus_controller:
  - id: epever
    address: 0x1   ## address of the ModBUS slave device on the bus
    modbus_id: modbus1
    setup_priority: -10

text_sensor:
  - name: "rtc_clock"
    platform: modbus_controller
    modbus_controller_id: epever
    id: rtc_clock
    internal: true
    register_type: holding
    address: 0x9013    ## address of the register inside the ModBUS slave device
    register_count: 3
    raw_encode: HEXBYTES
    response_size: 6

switch:
  - platform: modbus_controller
    modbus_controller_id: epever
    id: reset_to_fabric_default
    name: "Reset to Factory Default"
    register_type: coil
    address: 0x15
    bitmask: 1

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

Bitmasks¶

Some devices use decimal values in read registers to show multiple binary states occupying only one register address. To decode them, you can use bitmasks according to the table below. The decimal value corresponding to a bit is always double of the previous one in the row. Multiple bits can be represented in a single register by making a sum of all the values corresponding to the bits.

Alarm bit	Description	DEC value	HEX value
bit 0	Binary Sensor 0	1	1
bit 1	Binary Sensor 1	2	2
bit 2	Binary Sensor 2	4	4
bit 3	Binary Sensor 3	8	8
bit 4	Binary Sensor 4	16	10
bit 5	Binary Sensor 5	32	20
bit 6	Binary Sensor 6	64	40
bit 7	Binary Sensor 7	128	80
bit 8	Binary Sensor 8	256	100
bit 9	Binary Sensor 9	512	200
bit 10	Binary Sensor 10	1024	400
bit 11	Binary Sensor 11	2048	800
bit 12	Binary Sensor 12	4096	1000
bit 13	Binary Sensor 13	8192	2000
bit 14	Binary Sensor 14	16384	4000
bit 15	Binary Sensor 15	32768	8000

For example, when reading register 15, a decimal value of 12288 is the sum of 4096 + 8192, meaning the corresponding bits 12 and 13 are 1, the other bits are 0.

To gather some of these bits as binary sensors in ESPHome, use bitmask:

binary_sensor:
- platform: modbus_controller
  modbus_controller_id: ventilation_system
  name: Alarm bit0
  entity_category: diagnostic
  device_class: problem
  register_type: read
  address: 15
  bitmask: 0x1
- platform: modbus_controller
  modbus_controller_id: ventilation_system
  name: Alarm bit1
  entity_category: diagnostic
  device_class: problem
  register_type: read
  address: 15
  bitmask: 0x2
- platform: modbus_controller
  modbus_controller_id: ventilation_system
  name: Alarm bit10
  entity_category: diagnostic
  device_class: problem
  register_type: read
  address: 15
  bitmask: 0x400
- platform: modbus_controller
  modbus_controller_id: ventilation_system
  name: Alarm bit15
  entity_category: diagnostic
  device_class: problem
  register_type: read
  address: 15
  bitmask: 0x8000

Protocol decoding example¶

sensors:
  - platform: modbus_controller
    modbus_controller_id: epever
    id: array_rated_voltage
    name: "array_rated_voltage"
    address: 0x3000
    unit_of_measurement: "V"
    register_type: read
    value_type: U_WORD
    accuracy_decimals: 1
    skip_updates: 60
    filters:
      - multiply: 0.01

  - platform: modbus_controller
    modbus_controller_id: epever
    id: array_rated_current
    name: "array_rated_current"
    address: 0x3001
    unit_of_measurement: "V"
    register_type: read
    value_type: U_WORD
    accuracy_decimals: 2
    filters:
      - multiply: 0.01

  - platform: modbus_controller
    modbus_controller_id: epever
    id: array_rated_power
    name: "array_rated_power"
    address: 0x3002
    unit_of_measurement: "W"
    register_type: read
    value_type: U_DWORD_R
    accuracy_decimals: 1
    filters:
      - multiply: 0.01

  -platform: modbus_controller
    modbus_controller_id: epever
    id: battery_rated_voltage
    name: "battery_rated_voltage"
    address: 0x3004
    unit_of_measurement: "V"
    register_type: read
    value_type: U_WORD
    accuracy_decimals: 1
    filters:
      - multiply: 0.01

  - platform: modbus_controller
    modbus_controller_id: epever
    id: battery_rated_current
    name: "battery_rated_current"
    address: 0x3005
    unit_of_measurement: "A"
    register_type: read
    value_type: U_WORD
    accuracy_decimals: 1
    filters:
      - multiply: 0.01

  - platform: modbus_controller
    modbus_controller_id: epever
    id: battery_rated_power
    name: "battery_rated_power"
    address: 0x3006
    unit_of_measurement: "W"
    register_type: read
    value_type: U_DWORD_R
    accuracy_decimals: 1
    filters:
      - multiply: 0.01

  - platform: modbus_controller
    modbus_controller_id: epever id: charging_mode
    name: "charging_mode"
    address: 0x3008
    unit_of_measurement: ""
    register_type: read
    value_type: U_WORD
    accuracy_decimals: 0

To minimize the required transactions all registers with the same base address are read in one request. The response is mapped to the sensor based on register_count and offset in bytes. For example:

Request

data	description
0x1 (01)	device address
0x4 (04)	function code 4 (Read Input Registers)
0x30 (48)	start address high byte
0x0 (00)	start address low byte
0x0 (00)	number of registers to read high byte
0x9 (09)	number of registers to read low byte
0x3f (63)	crc
0xc (12)	crc

Response

offset	data	value (type)	description
H	0x1 (01)		device address
H	0x4 (04)		function code
H	0x12 (18)		byte count
0	0x27 (39)	U_WORD	array_rated_voltage high byte
1	0x10 (16)	0x2710 (100000)	array_rated_voltage low byte
2	0x7 (7)	U_WORD	array_rated_current high byte
3	0xd0 (208)	0x7d0 (2000)	array_rated_current low byte
4	0xcb (203)	U_DWORD_R	array_rated_power high byte of low word
5	0x20 (32)	spans 2 register	array_rated_power low byte of low word
6	0x0 (0)		array_rated_power high byte of high word
7	0x0 (0)	0x0000CB20 (52000)	array_rated_power low byte of high word
8	0x9 (09)	U_WORD	battery_rated_voltage high byte
9	0x60 (96)	0x960 (2400)	battery_rated_voltage low byte
10	0x7 (07)	U_WORD	battery_rated_current high word
11	0xd0 (208)	0x7d0 (2000)	battery_rated_current high word
12	0xcb (203)	U_DWORD_R	battery_rated_power high byte of low word
13	0x20 (32)	spans 2 register	battery_rated_power low byte of low word
14	0x0 (0)		battery_rated_power high byte of high word
15	0x0 (0)	0x0000CB20 (52000)	battery_rated_power low byte of high word
16	0x0 (0)	U_WORD	charging_mode high byte
17	0x2 (02)	0x2 (MPPT)	charging_mode low byte
C	0x2f (47)		crc
C	0x31 (49)		crc

Note

Write support is only implemented for switches and selects. However the C++ code provides the required API to write to a ModBUS device.

These methods can be called from a lambda.

Here is an example how to set config values to for an EPEVER Trace AN controller. The code synchronizes the localtime of MCU to the epever controller The time is set by writing 12 bytes to register 0x9013. Then battery charge settings are sent.

esphome:
  on_boot:
    ## configure controller settings at setup
    ## make sure priority is lower than setup_priority of modbus_controller
    priority: -100
    then:
      - lambda: |-
          // get local time and sync to controller
          time_t now = ::time(nullptr);
          struct tm *time_info = ::localtime(&now);
          int seconds = time_info->tm_sec;
          int minutes = time_info->tm_min;
          int hour = time_info->tm_hour;
          int day = time_info->tm_mday;
          int month = time_info->tm_mon + 1;
          int year = time_info->tm_year % 100;
          esphome::modbus_controller::ModbusController *controller = id(epever);
          // if there is no internet connection localtime returns year 70
          if (year != 70) {
            // create the payload
            std::vector<uint16_t> rtc_data = {uint16_t((minutes << 8) | seconds), uint16_t((day << 8) | hour),
                                              uint16_t((year << 8) | month)};
            // Create a ModBUS command item with the time information as the payload
            esphome::modbus_controller::ModbusCommandItem set_rtc_command =
                esphome::modbus_controller::ModbusCommandItem::create_write_multiple_command(controller, 0x9013, 3, rtc_data);
            // Submit the command to the send queue
            epever->queue_command(set_rtc_command);
            ESP_LOGI("ModbusLambda", "EPSOLAR RTC set to %02d:%02d:%02d %02d.%02d.%04d", hour, minutes, seconds, day, month,
                    year + 2000);
          }
          // Battery settings
          // Note: these values are examples only and apply my AGM Battery
          std::vector<uint16_t> battery_settings1 = {
              0,       // 9000 Battery Type 0 =  User
              0x0073,  // 9001 Battery Cap 0x55 == 115AH
              0x012C,  // 9002 Temp compensation -3V /°C/2V
              0x05DC,  // 9003 0x5DC == 1500 Over Voltage Disconnect Voltage 15,0
              0x058C,  // 9004 0x58C == 1480 Charging Limit Voltage 14,8
              0x058C,  // 9005 Over Voltage Reconnect Voltage 14,8
              0x05BF,  // 9006 Equalize Charging Voltage 14,6
              0x05BE,  // 9007 Boost Charging Voltage 14,7
              0x0550,  // 9008 Float Charging Voltage 13,6
              0x0528,   // 9009 Boost Reconnect Charging Voltage 13,2
              0x04C4,  // 900A Low Voltage Reconnect Voltage 12,2
              0x04B0,  // 900B Under Voltage Warning Reconnect Voltage 12,0
              0x04BA,  // 900c Under Volt. Warning Volt 12,1
              0x04BA,  // 900d Low Volt. Disconnect Volt. 11.8
              0x04BA   // 900E Discharging Limit Voltage 11.8
          };

          // Boost and equalization periods
          std::vector<uint16_t> battery_settings2 = {
              0x0000,  // 906B Equalize Duration (min.) 0
              0x0075   // 906C Boost Duration (aka absorb) 117 mins
          };
          esphome::modbus_controller::ModbusCommandItem set_battery1_command =
              esphome::modbus_controller::ModbusCommandItem::create_write_multiple_command(controller, 0x9000, battery_settings1.size() ,
                                                                                          battery_settings1);

          esphome::modbus_controller::ModbusCommandItem set_battery2_command =
              esphome::modbus_controller::ModbusCommandItem::create_write_multiple_command(controller, 0x906B, battery_settings3.size(),
                                                                                          battery_settings2);
          delay(200) ;
          controller->queue_command(set_battery1_command);
          delay(200) ;
          controller->queue_command(set_battery2_command);
          ESP_LOGI("ModbusLambda", "EPSOLAR Battery set");

uart:
  id: mod_bus
  tx_pin: 19
  rx_pin: 18
  baud_rate: 115200
  stop_bits: 1

modbus:
  #flow_control_pin: 23
  send_wait_time: 200ms
  id: mod_bus_epever

modbus_controller:
  - id: epever
    ## the Modbus device addr
    address: 0x1
    modbus_id: mod_bus_epever
    command_throttle: 0ms
    setup_priority: -10
    update_interval: ${updates}

sensor:
  - platform: modbus_controller
    modbus_controller_id: epever
    id: array_rated_voltage
    name: "array_rated_voltage"
    address: 0x3000
    unit_of_measurement: "V"
    register_type: read
    value_type: U_WORD
    accuracy_decimals: 1
    filters:
      - multiply: 0.01

  - platform: modbus_controller
    modbus_controller_id: epever
    id: array_rated_current
    name: "array_rated_current"
    address: 0x3001
    unit_of_measurement: "A"
    register_type: read
    value_type: U_WORD
    accuracy_decimals: 2
    filters:
      - multiply: 0.01

  - platform: modbus_controller
    modbus_controller_id: epever
    id: array_rated_power
    name: "array_rated_power"
    address: 0x3002
    unit_of_measurement: "W"
    register_type: read
    value_type: U_DWORD_R
    accuracy_decimals: 1
    filters:
      - multiply: 0.01

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