The use of the ESP8266 in the world of IoT

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By martinayotte
#55330 Yes, ESP-12 and ESP-01 are programmed the same way with Arduino IDE, the only thing is the number of GPIOs.

For I2C bus schematic, it only requires to have PullUps on 2 GPIOs and attach the MCP23017 on this bus.
Since GPIO2/GPIO0 have already PullUps for boot process, they are perfect to be used as I2C bus.