Arduino, ESP and i2c devices

This project permits to control a remote LCD display connected via an i2c port expander via Wifi.

I have successfully tested this program on an ESP-12 (ESP8266) using the Arduino IDE.

hardware

The hardware "ingredients" needed for this experiments are:

• a ESP8266 (in the example it is a ESP12).
• an lcd-plug by jeelabs including the display
• A "console cable" (but any USB to TTL converter is okay).

wiring

i2c: SDA is GP04, SCL is GP05. The pins of jeelabs' lcd plug (this cabling works for all i2c based jeelabs' plugs):

• P -> +5V or disconnected (unused for lcd-plug)
• D -> GP04 (SDA)
• G -> GND
• + -> +3V3
• A -> GP05 (SCL)
• I -> NC (unused for lcd-plug, can be connected to another GPIO for other boards providing useful interrupts).

Console cable: using an Adafruit like cable:

• Black -> GROUND
• While -> TXD on ESP
• Green -> RXD on ESP

DO NOT CONNECT THE RED PIN TO YOUR ESP! The red pin is +5V while ESP need +3V3 so either you have a step-down circuit to convert 5V to 3.3V or you'll need another power source of the right voltage for yout ESP.

Software

Here is the source code. <source lang=C>