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- ---
- -- @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
- ---------------------------------------------------------------------------------------------
- local mcp23008 = require ("mcp23008")
- -- ESP-01 GPIO Mapping as per GPIO Table in https://github.com/nodemcu/nodemcu-firmware
- local gpio0, gpio2 = 3, 4
- ---
- -- @name showButtons
- -- @description Shows the state of each GPIO pin
- -- @return void
- ---------------------------------------------------------
- local function showButtons()
- local 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
- do
- -- Setup the MCP23008
- mcp23008.begin(0x0,gpio2,gpio0,i2c.SLOW)
- mcp23008.writeIODIR(0xff)
- mcp23008.writeGPPU(0xff)
- tmr.create():alarm(2000, tmr.ALARM_AUTO, showButtons) -- run showButtons() every 2 seconds
- end
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