This article shows you how to build a device to remotely read data from an electric meter (or any device with a compatible interface).
It uses widely available components, open source software and is compatible with popular home automation software, Home Assistant.
A kit for assembling a functional device is available for purchase on Tindie: PiggyMeter KIT.
Supports IEC62056-21 based protocols
Multiple meters: energy, water, thermal, and more
Uses open source ESPHome
Wireless communication via Wi-Fi
Integrates with Home Assistant
Cheap hardware ESP32-C3 or ESP32-S2
Case design available for 3D print
It supports meters compatible with IEC62056-21 standard that works in modes A, B, C, D (but not E). For details see ESPHome IEC 62056-21 Component.
Note that there are many variations of the protocol. Although the meter may use the same optical interface, the data frame format could be different.
SML and DSML standards are not supported.
How to check if the meter is supported?
IEC 62056-21 term is used for multiple protocols (with the same hardware layer but different data encoding). The device supports meters that provide ASCII-encoded data, something like this:
1-0:15.8.1(00000009999.567*kWh) 1-0:15.8.2(00000000000.000*kWh) 1-0:15.8.3(00000000000.000*kWh) 1-0:15.8.4(00000000000.000*kWh)
The meter must be compatible with International Standard IEC 62056-21:2002.
Bill of materials
Wemos C3 or S2 Mini https://www.wemos.cc/en/latest/
PiggyMeter PCB https://www.tindie.com/products/32082/
2×pin header 1×4
2.54mm raster; plastic part must be 8.5 mm height
3D printed case https://github.com/aquaticus/piggymeter_case
3D printed washer https://github.com/aquaticus/piggymeter_case
3D printed back lid https://github.com/aquaticus/piggymeter_case
You need a board with Espressif chip installed and compatible Wemos/Lolin pinout. The key factor is location of 4 pins: GND, VCC, TX, and RX.
The size of the PCB is also critical. 3D printed case matches only boards (or their clones) listed below:
Lolin/Wemos S2 mini
Lolin/Wemos C2 mini
In theory, you can use any other CPU board with compatible pinout, notable ESP32 and ESP8266 D1 mini. But in that case you must design your own case and modify a bit configuration files (board type and serial port pins).
A meter employs an optical interface compatible with IEC62056-21 standard, communicating with a probe via an infrared diode and a phototransistor.
The interface is connected to one of the serial ports on CPU board. Of course you need VCC and GND too.
Solder 2 pin headers. You must use pin header 8.5 mm height. The design of the case accommodates this height, ensuring a proper fit. If the height exceeds this dimension, closing the lid may pose challenges.
You can buy assembled interface on Tindie.
Download files for 3D printer from https://github.com/aquaticus/piggymeter_case.
The casing comprises three components:
the main case,
and a lid.
There are three distinct STL files available for each component, or alternatively, a single 3fm file incorporating all three elements.
The housing meets the requirements of the IEC62056-21 standard.
The housing has a small latch. To close or open it, you need to use some force.
Recommended 3D print settings
Layer: 0.2 mm
Arrange the components within the case in this order:
Begin by installing ESPHome.
Based on your CPU board, select the appropriate configuration file. Additionally, make manual adjustments to certain parameters, such as the WiFi password.
Get configuration files
Clone git repository with configuration files:
git clone https://github.com/aquaticus/piggymeter_esphome_yaml
Create secrets.yaml file
Create a secrets.yaml file within the directory where the configuration files are located. This file will hold the WiFi network name and its corresponding password.
# Home Assistant API encryption key api_key: my_home_assistant_encryption_key # OTA password ota_pass: my_ota_password # WiFi network name wifi_ssid: my_network # WiFi network password wifi_pass: my_password
Modify project configuration
The configuration comes pre-set with standard data points for an electric meter.
Feel free to adjust the list, especially if your meter differs from the electric meter type. Refer to the ESPHome IEC 62056-21 Component for further information.
sensor: - platform: iec62056 obis: 1-0:15.8.0 name: Absolute active energy total unit_of_measurement: kWh accuracy_decimals: 3 device_class: energy state_class: total_increasing
Build and flash the firmware
esphome run piggymeter-s2-iec62056-21.yaml
The command above flashes the firmware and show monitor output. By default, the interface reads data from a meter every 1 minute.
[12:21:27][D][iec62056.component:232]: Connection start [12:21:27][D][binary_sensor:036]: 'Meter Connection Status': Sending state ON [12:21:28][D][switch:013]: 'Internal LED' Turning ON. [12:21:28][D][switch:056]: 'Internal LED': Sending state ON [12:21:28][D][iec62056.component:174]: Meter identification: '/XXX6\2YYYYY' [12:21:28][D][iec62056.component:407]: Meter reported protocol: C [12:21:28][D][iec62056.component:410]: Meter reported max baud rate: 19200 bps ('6') [12:21:28][D][iec62056.component:438]: Using negotiated baud rate 9600 bps. [12:21:29][D][iec62056.component:470]: Switching to new baud rate 9600 bps ('5') [12:21:29][D][iec62056.component:482]: Meter started readout transmission [12:21:29][D][iec62056.component:524]: Data: 0-0:C.1.0(12345678) [12:21:29][D][iec62056.component:524]: Data: 0-0:1.0.0(2000-01-01 20:10:30) [12:21:29][D][iec62056.component:524]: Data: 1-0:15.8.0(00000001000.657*kWh) [12:21:29][D][iec62056.component:620]: Set sensor 'Absolute active energy total' for OBIS '1-0:15.8.0'. Value: 1000.656982 [12:21:29][D][iec62056.component:524]: Data: 1-0:15.8.1(00000002000.657*kWh) [12:21:29][D][iec62056.component:524]: Data: 1-0:15.8.2(00000003000.000*kWh) [12:21:29][D][iec62056.component:524]: Data: 1-0:15.8.3(00000004000.000*kWh) [12:21:29][D][iec62056.component:524]: Data: 1-0:15.8.4(00000005000.000*kWh) [12:21:29][D][iec62056.component:524]: Data: 1-0:15.6.0(00000006000.385*kW)(2000-01-01 20:10:01)
The device should be automatically detected by Home Assistant. If not, you can add it manually by clicking Add Integration and selecting ESPHome integration.
PiggyMeter exposes three group of items:
This trigger force PiggyMeter to read data from a meter out of the schedule.
Meter Connection Status
Connected status indicates the interface is exchanging data with the meter.
This is a list of sensors defined in configuration file.
By default, the device fetches data every minute, and the internal LED is illuminated during transmission.
Only limited number of OBIS codes are defined in configuration yaml file. It is highly recommended to modify the list of sensors to mach a meter.
Although OBIS codes are standardized, meters may transmit varying numbers of codes. To ascertain the supported codes for your meter, enable DEBUG logging for the iec62056 component and analyze the log output.
Diagnostic and Problems
After flashing the firmware, the device will attempt to read data from a meter after approximately 15 seconds. If the transmission fails, it will retry twice every 15 seconds.
You can adjust these parameters by configuring the appropriate tokens. Consult ESPHome IEC 62056-21 Component documentation for more details.
It’s advisable to switch the default log level from
once the device has been confirmed to work correctly.
Below are common issues and their respective solutions.
Ensure the probe is securely attached to the meter, aligning the arrow on the probe in an upward direction.
No transmission from meter
[E][iec62056.component:268]: No transmission from meter.
This may indicate:
Most commonly, the interface is not attached to a meter.
The interface isn’t properly aligned with the optical interface of a meter.
The meter is not compatible.
Not all sensors received data
[E][iec62056.component:644]: Not all sensors received data from the meter. The first one: OBIS '1-0:72.7.0'. Verify sensor is defined with valid OBIS code.
This may indicate two problems:
The meter does not support OBIS code you configured in yaml file. Simply remove sensor with specific OBIS code from configuration.
There might be a typo or incorrect definition of the OBIS code for the sensor in the configuration file. Double-check the code.
The meter transmits data automatically but the device receives nothing
This indicates the meter supports mode D of IEC62056-21. In this mode, the meter autonomously transmits data every few seconds without requiring a specific request. Ensure that the serial port is configured to align with the meter’s transmission format, typically set at 9600 7E1 or 2400 7E1 in most instances.
# 9600bps for mode D uart: rx_pin: GPIO21 tx_pin: GPIO22 baud_rate: 9600 data_bits: 7 parity: EVEN stop_bits: 1
In addition, Mode D must be manually activated by setting mode_d=True in the platform configuration.
# Enable mode D iec62056: mode_d: True
[E][iec62056.component:504]: BCC verification failed. Expected 0x6b, got 0x14
This error suggests transmission issues.
Usually, the transmission speed is excessively high. Lowering the maximum baud rate should help.
iec62056: baud_rate_max : 4800