-- @description Shows how to read 8 GPIO pins/buttons via I2C with the MCP23008 I/O expander. -- Tested on NodeMCU 0.9.5 build 20150213. -- @circuit -- Connect GPIO0 of the ESP8266-01 module to the SCL pin of the MCP23008. -- Connect GPIO2 of the ESP8266-01 module to the SDA pin of the MCP23008. -- Use 3.3V for VCC. -- Connect switches or buttons to the GPIOs of the MCP23008 and GND. -- Connect two 4.7k pull-up resistors on SDA and SCL -- We will enable the internal pull up resistors for the GPIOS of the MCP23008. -- @author Miguel (AllAboutEE) -- GitHub: https://github.com/AllAboutEE -- YouTube: https://www.youtube.com/user/AllAboutEE -- Website: http://AllAboutEE.com --------------------------------------------------------------------------------------------- require ("mcp23008") -- ESP-01 GPIO Mapping as per GPIO Table in https://github.com/nodemcu/nodemcu-firmware gpio0, gpio2 = 4, 3 -- Setup the MCP23008 mcp23008.begin(0x0,gpio2,gpio0,i2c.SLOW) mcp23008.writeIODIR(0xff) -- Set all GPIO pins as inputs mcp23008.writeGPPU(0xff) -- Set all pull ups on pins -- @name showButtons -- @description Shows the state of each GPIO pin -- @return void --------------------------------------------------------- function showButtons() gpio = mcp23008.readGPIO() -- read the GPIO/buttons states -- get/extract the state of one pin at a time for pin=0,7 do local pinState = bit.band(bit.rshift(gpio,pin),0x1) -- extract one pin state -- change to string state (HIGH, LOW) instead of 1 or 0 respectively if(pinState == mcp23008.HIGH) then pinState = "HIGH" else pinState = "LOW" end print("Pin ".. pin .. ": ".. pinState) end print("\r\n") end tmr.alarm(0,2000,1,showButtons) -- run showButtons() every 2 seconds