Ethernet easy plug&play Plug&play Ethernet client for Industruino

This post aims to get you started with the Industruino Ethernet module with a plug&play example sketch. It uses a common HTTP GET request that can be easily modified for any API, or any specific TCP communication. The sketch requires 3 libraries:

• Ethernet2 this needs to be the Industruino version, as the SPI speed needs to be set to 4MHz
• UC1701 for the Industruino LCD
• Adafruit_SleepyDog for watchdog reset functionality 

1. Enable the watchdog timer with an interval of 20 seconds: if the code hangs for some reason so the watchdog does not get reset within 20 seconds, the unit reboots
2. MAC address: the Industruino D21G has a unique MAC address stored in the EEPROM of the RTC, this 8-byte MAC is retrieved and formatted to 6 bytes for IPv4
3. Check ETH module: the Ethernet module has 8KB non-volatile FRAM memory; we use this to check whether the module is connected by writing/reading a flag at address 0 of the FRAM
4. Start Ethernet: we can use a fixed IP address, or request via DHCP, using the parameter USE_DHCP at the top of the sketch
5. Connect to server: the sketch loop makes a connection to the TCP_SERVER at port TCP_SERVER_PORT
6. HTTP GET request: if a connection is established, the sketch retrieves www.arduino.cc/latest.txt and looks for the '200 OK' reply
7. If the connection to the server fails, Ethernet is restarted
8. At the start of the loop, the watchdog timer is reset