HomeAssistant DSMR P1 TCP/IP bridge (ESP8266)

Purpose

Using this sketch, one can integrate a DSMR with HomeAssistant. The DSMR's P1 port is connected using the ESP8266's UART which is configured such that the RX pin is inverted. No external inverter is required or special cable is needed. The ESP8266 runs a TCP server to which HomeAssistant connects to fetch the data, using the DSMR platform.

Tested with:

• Adafruit HUZZAH module
• Sagemcom T210-D: connected the P1 DATA pin directly with RX and used one of the ESP8266's pins to switch data transmission on and off by taking the DATA REQUEST line low and high.
• Landis+Gyr E350 ZCF110CCtFs2: a 1 KOhm pullup resistor to the 3.3V is required for the P1 DATA line. The DATA REQUEST line should be tied to the 5V HUZZAG's power supply permannently.

Implementation

Using a ESP8266, read DSMR telegrams from the P1 port and publish them over TCP/IP. In contrast to most other implementations which read the P1 port, no hardware inverter is required. By properly configuring the UART's receive pin, the input is inverted and can be used directly.

The implementation was tested using a Adafruit HUZZAH ESP8266 board, powered using an old mobile phone charger, connected to a Sagemcom T210-D and L+G ZCF110CCtFs2 metering devices with the UART RX pin connected to the P1's Data (pin #5), GND to Data GND (pin #3) and GPIO 04 connected to Data Request (pin #2). One can simply use an old fully wired (all four connections) RJ11 telephone wire for this. GPIO pin 4 is used to enable/disable sending by the P1 port by taking the Data Request line HIGH/LOW. The Sagemcom T210-D uses protocol DSMR P1 version 5.0. With a properly wired RJ12 connector, one probably can even power the board from the P1 port as well and omit the external power supply.

The older L+G ZCF110CCtFs2 requires a pullup resistor for the DATA line and the DATA REQUEST line should be tied to 5 Volts to make the device sending telegrams.

The sketch implements two equivalant CRC checking functions, one using a lookup table and another one which processes the message bit-by-bit. The one using the lookup table might be faster at the cost of more memory being used, but this was not tested. CRC checking is redundant because the DSMR parser used by the DSMR platform does CRC checking also, but it is included since I think this is the proper place for CRC checking and it is such fun to implement.

If you DSMR runs an older P1 protocol version without CRCs, you have to review the sketch and make the appropriate changes.

Over-the-air (OTA) programming is also implemented.

Configuration

I use the file credentials.h for the user names and passwords used in the script and exclude this file from git to keep stuff save. You can do the same or just edit the sketch and add the credentials:

• STASSID is your wifi's SSID
• STAPSK the pre-shared wifi key (wifi password)

Home Assistant

Assuming you know the IP address <IP-ADDRESS> the ESP8266 uses, add the following lines to the configuration.yaml file and restart HA.

sensor:
    - platform: dsmr
      host: <IP-ADDRESS>
      port: 2001
      dsmr_version: 5

If you want to test outside HA, just run telnet <IP-ADDRESS> 2001 and you should see a telegram every second. NB: the ESP8266 can only handle one TCP connection, so this works only if HA isn't connected.

LEDs

• On booting and connecting to wifi, the HUZZAH's blue led will be on continiously.
• Also, the blue led is on during over-the-air updates.
• The blue led flashes shortly with every telegram received from the P1 port.
• The red led will be turned on when a TCP client, i.e. HomeAssistant, is connected.

Links

• Adafruit HUZZAH ESP8266
• Adafruit HUZZAH ESP8266
• Arduino core for ESP8266 WiFi chip
• ESP8266 Arduino Core’s documentation
• Slimme meter on wikipedia
• P1 Companion Standard