This combines Tuan PM's port of the MQTT client library for ESP8266, ported from: MQTT client library for Contiki, zarya's I2C driver and the OLED driver here to make a WiFi MQTT display.

It subscribes to three MQTT topics and displays them on the OLED, the display I am using is this 0.96" 128x64 White OLED but similar displays are widely available (plenty on eBay).

Configuration

• I2C address for the OLED is in include/driver/i2c_oled.h
• MQTT broker and WiFi settings are in include/user_config.h
• GPIO pins to use for I2C are in driver/i2c.h
• MQTT topics to subscribe to are in the MQTT_Start() function in user/mqtt.c
• What to do with the incoming messages is defined in deliver_publish() in user/mqtt.c

If you want to add more than 3 topics you need to change MQTT_SUB_TOPIC_NUM in user_config.h and the mqtt_topic variable declaration near the top of mqtt.c

I haven't tested the Windows Makefile, it is as it comes with the MQTT demo.