Modbus Controller

The modbus_controller component creates a RS485 connection to control a modbus device

../_images/modbus.png

The modbus_controller component uses the modbus component

Hardware setup

A RS 485 module connected to an ESP32, for example:

../_images/rs485.jpg

See How is this RS485 Module Working? on stackexchange for more details

The controller connects to the UART of the MCU. For ESP32 GPIO PIN 16 to TXD PIN 17 to RXD are the default ports but any other pins can be used as well. 3.3V to VCC and GND to GND.

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 device Specify the modbus device address of the.

  • command_throttle (Optional, int): minimum time in milliseconds between 2 requests to the device. Default is 0ms Because some modbus devices limit the rate of requests the interval between sending requests to the device can be modified.

Example

The following code create 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
    ## the Modbus device addr
    address: 0x1
    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
    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.

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. 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

See Also