vitotronic-interface-8266

ESP8266 WiFi to serial interface, built to connect to a Viessmann Vitotronic heating control. The heating control is accessed by using an Optokoppler, according to the instructions in the OpenV wiki and made available as TCP/telnet server in the WiFi network. The communication bewteen the ESP8266 and the heating (via the Optokoppler) runs at 4800bps, 8 bits, even parity, 2 stop bits.

Flashing the Firmware

1. Install the Arduino IDE plus the 8266 package following the instructions at https://github.com/esp8266/Arduino#installing-with-boards-manager
2. Open, compile and upload the vitotronic-interface-8266.ino sketch to your ESP8266.

Setting Up the Optokoppler Hardware

• Wire up the ESP8266 and power supply.
• Connect the Optokoppler to the heating, connect IN/RX with the ESP8266 RX line and OUT/TX with the ESP8266 TX line, as well as VCC and GND to 3.3V and Ground.
• If you want to retrieve debugging output, connnect a serial port's RX line to GPIO2 of the ESP8266 at 115200bps, 8N1. Don't forget to connect GND of the port as well to GND of the ESP8266. Works like charm with an FTD USB-to-serial adapter.

Configuring the Adapter

As long as the ESP of the adapter is not configured for connecting to a WiFi network it will provide an own WPA2-secured WiFi access point for configuration. To set up the adapter,

• Scan your WiFi environment for the SSID "vitotronic-interface".
• Connect to this network, using the password "vitotronic".
• In your web browser, visit http://192.168.4.1
• Provide the required configuration information:
  • SSID of the WiFi network to connect to (mandatory)
  • Password for the WiFi network
  • If you want to assign a static IP to the adapter, specify
    • IP address to be assigned to the adapter
    • DNS server address
    • Gateway address
    • Subnet Mask
  • The Port at which the adapter listens for an incoming connection (mandatory)
• Press "Submit" afterwards. The adapter will save the configuration, restart and connect to the given WiFi network. Afterwards the server will be reachable in the network at the IP (DHCP or static) and specified port. The server's IP is also pingable. Important notice: Some ESP8266 modules need a "hard reset" to be able to connect to the new WiFi network. Therefore it is recommended to interrupt the power supply for a short time after the new configuration has been submitted. If the connection was successlful, the vitotronic-interface network will be gone and the adapter should be pingable in the specified network.

To re-configure the adapter, connect GPIO12 to GND for a short time (e.g. by a pushbutton). Thus, the existing configuration will be deleted and the adapter will enter setup mode again (see above).