An ESP8266 based smart meter (SML) to HTTP->JSON Main Purpose is an easy access for EVCC to read the Smart Meter Grid
The aim of this project is to read the meter readings of modern energy meters and make them available via HTTP.
The software was primarily developed and tested for the EMH ED300L electricity meter, but should also work with other energy meters that have an optical interface and communicate via the SML protocol.
SMLReader publishes the metrics read from the meter's optical unit to an HTTP Site in a JSON format for easiest readout for EVCC Charger.
If you like this project, you might consider to support me.
The following config will connect to the Meter and collect the actual Grid Power.
meters:
- name: grid1
type: custom
power: # Leistung (W)
source: http
uri: http://192.168.XXX.XXX/api/data/json
method: GET # default HTTP method
headers:
- content-type: application/json
auth: # basic authorization
type: basic
user: admin
password: <Password>
insecure: true # set to true to trust self-signed certificates
jq: .Power # parse response json
scale: 1 # floating point factor applied to result, e.g. for kW to W conversion
timeout: 5s # timeout in golang duration format, see https://golang.org/pkg/time/#ParseDuration
The reading head consists of a phototransistor (BPW 40) and a 1 kΩ pull-up resistor connected to one of the GPIO pins of the microcontroller. Other phototransistors or the use of an internal pull-up resistor will probably work, too.
The housing of my reading head has been 3D-printed using the STL files from Stefan Weigert.
A ring magnet (in my case dimensioned 27x21x3mm) ensures that the reading head keeps stuck on the meter.
The phototransistor has been fixed with hot glue within the housing.
To get started, the software must first somehow get onto the device. This can be done in several ways.
This precompiled binary can be flashed to the device with the help of esptool.py. Other tools should also work, as long as you have configured them to match the specs of your ESP8266.
esptool.py --port /dev/ttyUSB0 write_flash -fm dout 0x00000 path/to/smlreader.binAs a docker enthusiast I prefer to utilize a dockerized version of esptool.py by bind-mounting the current working directory to /src and assuming that smlreader.bin is existing in the current working directory:
docker run -it --device /dev/ttyUSB0 -v $(pwd):/src --rm mruettgers/esptool --port /dev/ttyUSB0 write_flash -fm dout 0x00000 /src/smlreader.binThe device path and the path to the binary have to be adjusted to fit your needs.
You should be able to use your preferred IDE to build and flash SMLReader if you take care of the dependencies and the build flags configured in the platform.io file.
I strongly recommend using PlatformIO as it takes care of that itself.
The configuration of the reading heads is done by editing src/config.h and adjusting SENSOR_CONFIGS (see below).
static const SensorConfig SENSOR_CONFIGS[] = {
{.pin = D2, // GPIO pin of the phototransistor
.name = "1", // Sensor name used in MQTT topic
.numeric_only = false, // If "true", only numeric values are being published via MQTT
.status_led_enabled = true, // Flash status LED (3 times) when an SML start sequence has been found
.status_led_inverted = true, // Some LEDs (like the ESP8266 builtin LED) require an inverted output signal
.status_led_pin = LED_BUILTIN, // GPIO pin used for sensor status LED
.interval = 0 // If greater than 0, messages are published every [interval] seconds
},
{.pin = D5,
.name = "2",
.numeric_only = false,
.status_led_enabled = true,
.status_led_inverted = true,
.status_led_pin = LED_BUILTIN,
.interval = 0
},
{.pin = D6,
.name = "3",
.numeric_only = false,
.status_led_enabled = true,
.status_led_inverted = true,
.status_led_pin = LED_BUILTIN,
.interval = 15
}
};Building SMLReader in PlatformIO is straight forward and can be done by executing the build task matching your environment (i.e. d1_mini).
In case you get the following error, it is time to install a Git client (https://git-scm.com/downloads) and to make sure that the path to git is covered by the PATH variable and git is thus executable from everywhere.
UserSideException: Please install Git client from https://git-scm.com/downloads:
File "/home/monty/.platformio/penv/lib/python3.8/site-packages/platformio/builder/main.py", line 168:
env.SConscript("$BUILD_SCRIPT")
WiFi is configured via the web interface provided by IotWebConf and which can be reached after joining the WiFi network named SMLReader and heading to http://192.168.4.1.
If the device has already been configured, the web interface can be reached via the IP address obtained from your local network's DHCP server.
To login provide the user admin and the configured AP password.
Attention: You have to change the AP Password (empty by default), otherwise SMLReader won't work.
If everything is configured properly and running with a sensor in place, SMLReader will publish the metrics and values received from the meter to http:
Serial logging can be enabled by setting SERIAL_DEBUG=true in the platformio.ini file before building.
To increase the log level and to get the raw SML data, also set SERIAL_DEBUG_VERBOSE=true.
A serial port monitor can be attached using the corresponding function of your IDE or by invoking a terminal client like miniterm which comes shipped with python-serial.
The serial port settings are 115200,8,N,1.
miniterm /dev/ttyUSB0 115200nb-ubuntu ➜ ~/Downloads miniterm /dev/ttyUSB0 115200
--- Miniterm on /dev/ttyUSB0 115200,8,N,1 ---
--- Quit: Ctrl+] | Menu: Ctrl+T | Help: Ctrl+T followed by Ctrl+H ---
Config size: 685
Wrong config version.
AP password was not set in configuration
State changing from: 0 to 1
Setting up AP: SMLReader
With default password: <hidden>
AP IP address: 192.168.4.1
State changed from: 0 to 1
...
- https://www.msxfaq.de/sonst/bastelbude/smartmeter_d0_sml_protokoll.htm
- https://www.photovoltaikforum.com/thread/78798-sml-pr%C3%BCfsummenberechnung-ich-verzweifle-an-crc/ (Helped me to finally solve some weird CRC calculation issues before switching over to libSML)
- http://www.stefan-weigert.de/php_loader/sml.php (Sources of the 3D-printed housing of the reading head)
- https://github.com/gemu2015/Sonoff-Tasmota (Gemu's excellent Tasmota version with SML support)
Distributed under the GPL v3 license.
See LICENSE for more information.