Unit VMeter Home Assistant Integration

This section describes the configuration methods and practical steps for integrating the Unit VMeter voltage sensor into Home Assistant.

Tutorial

• ADS1115 Datasheet
• Get the latest configuration for ADS1115 from ESPHome: ADS1115 4-Channel 16-Bit A/D Converter

Note

Unit VMeter is only a standalone sensor platform and requires an additional controller device (such as Atom series, Stamp series, Stick series, Core/Basic series, etc.) to be integrated into Home Assistant.

Learn

1. The I²C component must be enabled in the ESPHome configuration:

   # Example configuration entry for ESP32
   i2c:
     sda: GPIOXX
     scl: GPIOXX
     scan: true

   # Example configuration entry for ESP32 i2c: sda: GPIOXX scl: GPIOXX scan: true

The GPIO pins will vary depending on the controller device used. For example, using Atom Lite as the controller:

# I2C Bus on Grove Port (HY2.0-4P)
i2c:
  sda: GPIO26
  scl: GPIO32

Unit VMeter Configuration Example:

1. First, configure the basic component ADS1115:

   yaml ads1115: - address: 0x49 sensor: - platform: ads1115 multiplexer: "A0_A1" gain: 1.024 sample_rate: 128 name: "Unit VMeter A0_A1 Ref" id: diff update_interval: 10s

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   ads1115:
     - address: 0x49
   
   sensor:
     - platform: ads1115
       multiplexer: "A0_A1"
       gain: 1.024
       sample_rate: 128
       name: "Unit VMeter A0_A1 Ref"
       id: diff
       update_interval: 10s

2. Configure EEPROM to read calibration parameters and combine with a Template Sensor to create custom data:

   yaml i2c_device: id: eeprom address: 0x53 sensor: # Previous ads1115 declarations ... - platform: template name: "Input Voltage" id: input_volt unit_of_measurement: "V" icon: "mdi:flash" accuracy_decimals: 2 update_interval: 10s lambda: |- float d = id(diff).state; if (isnan(d)) return NAN; const float PRESSURE_COEFF = 0.015918958f; // Remember to change the 'EEPROM_REG' if you changed the 'gain' const uint8_t EEPROM_REG = 0xE8; uint8_t calib[8]; uint16_t hope, actual; // Read EEPROM if ( id(eeprom).read_register(EEPROM_REG, calib, 8) != i2c::ERROR_OK ) { ESP_LOGD("vmeter.sensor", "Failed to read from EEPROM.."); return NAN; } uint8_t xor_result = 0x00; for (uint8_t i = 0; i < 5; i++) { xor_result ^= calib[i]; } if (xor_result != calib[5]) { return NAN; } hope = (calib[1] << 8) | calib[2]; actual = (calib[3] << 8) | calib[4]; float calibration_ratio = (float)hope / actual; ESP_LOGD("vmeter.sensor", "Factory calibration factor: %f", calibration_ratio); float vin = - d / PRESSURE_COEFF; vin = vin * calibration_ratio; return vin;

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   i2c_device:
     id: eeprom
     address: 0x53
   
   sensor:
     # Previous ads1115 declarations
     ...
     - platform: template
       name: "Input Voltage"
       id: input_volt
       unit_of_measurement: "V"
       icon: "mdi:flash"
       accuracy_decimals: 2
       update_interval: 10s
       lambda: |-
   
         float d = id(diff).state;
   
         if (isnan(d)) return NAN;
   
         const float PRESSURE_COEFF = 0.015918958f;
   
         // Remember to change the 'EEPROM_REG' if you changed the 'gain'
         const uint8_t EEPROM_REG = 0xE8;
   
         uint8_t calib[8];
         uint16_t hope, actual;
   
         // Read EEPROM
         if ( id(eeprom).read_register(EEPROM_REG, calib, 8) != i2c::ERROR_OK ) {
           ESP_LOGD("vmeter.sensor", "Failed to read from EEPROM..");
           return NAN;
         }
   
         uint8_t xor_result = 0x00;
   
         for (uint8_t i = 0; i < 5; i++) {
             xor_result ^= calib[i];
         }
   
         if (xor_result != calib[5]) {
           return NAN;
         }
   
         hope   = (calib[1] << 8) | calib[2];
         actual = (calib[3] << 8) | calib[4];
   
         float calibration_ratio = (float)hope / actual;
   
         ESP_LOGD("vmeter.sensor", "Factory calibration factor: %f", calibration_ratio);
   
         float vin = - d / PRESSURE_COEFF;
         vin = vin * calibration_ratio;
   
         return vin;

3. When reading the EEPROM, the EEPROM_REG read address in the lambda expression must be modified based on the gain value set for the ADS1115:

   c++ // In lambda expression // remember to change the 'EEPROM_REG' if you changed the 'gain' // for an example, when 'gain' is 1.024 const uint8_t EEPROM_REG = 0xE8;

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   // In lambda expression
   // remember to change the 'EEPROM_REG' if you changed the 'gain'
   // for an example, when 'gain' is 1.024
   const uint8_t EEPROM_REG = 0xE8;

The recommended gain values are 0.256, 0.512, and 1.024; among them, the resolution is 1mV for measuring voltages below 16V, and 7.9mV for voltages above 16V. Please select the most appropriate gain value and read the corresponding calibration parameters in the EEPROM according to the target voltage. For data accuracy, only one channel (AIN0 or AIN1) can be measured at a time. Do not connect voltage inputs to both channels simultaneously.

Quick Start

Once added to the Dashboard, you can view the sensor data in Home Assistant.

Video