Copyright
NodeMCU Development Workshop Agus Kurniawan 1st Edition, 2015 Copyright © 2015 Agus Kurniawan
Table of Contents Copyright Preface 1. Preparing Development Environment 1.1 NodeMCU 1.2 Electronics Components 1.2.1 Arduino Starter Kit 1.2.2 Fritzing 1.2.3 Cooking-Hacks: Arduino Starter Kit 1.2.4 Arduino Sidekick Basic kit v2 1.2.5 Grove - Starter Kit for Arduino 1.2.6 DFRobot - Arduino Kit for Beginner v3 1.3 Development Tools 1.4 Testing 2. Setting Up NodeMCU 2.1 Getting Started 2.2 Connecting NodeMCU board to Computer 2.3 Flashing The Latest NodeMCU Firmware 2.3.1 Windows Platform 2.3.2 Linux and OS X Platforms 2.4 Development Tools 2.4.1 Serial/UART Tool
2.4.2 Arduino IDE 2.4.3 NodeMCU Studio 2.5 Hello NodeMCU: Blinking LED 2.5.1 Wiring 2.5.2 Writing Program Using Serial/UART Tool 2.5.3 Uploading Lua Script File to NodeMCU Board 3. Lua Programming Language 3.1 Preparing Development Environment 3.2 Common Rule 3.3 Variables 3.3.1 Declaring Variable 3.3.2 Assigning Variables 3.3.3 Demo 3.4 Comment 3.5 Arithmetic Operations 3.6 Mathematical Functions 3.7 Increment and Decrement 3.8 Comparison Operators 3.9 Logical Operators 3.10 Decision - if..then 3.11 Iteration - for 3.12 Iteration - while 3.13 Iteration - repeat
3.14 break and do 3.15 Array 3.16 Functions 3.17 Lua Modules 4. GPIO Programming 4.1 Getting Started 4.2 Wiring 4.3 Writing a Program 4.4 Testing 5. PWM and Analog Input 5.1 Getting Started 5.2 Demo Analog Output (PWM) : RGB LED 5.2.1 Wiring 5.2.2 Writing Program 5.2.3 Testing 5.3 Demo Analog Input: Working with Potentiometer 5.3.1 Wiring 5.3.2 Writing Program 5.3.3 Testing 6. Working with I2C 6.1 Getting Started 6.2 Writing Program 6.3 Writing Program
6.4 Testing 7. UART 7.1 Getting Started 7.2 Wiring 7.3 Writing a Program 7.4 Testing 8. SPI 8.1 Getting Started 8.2 Wiring 8.3 Writing a Program 8.4 Testing 9. Working with OLED Display 9.1 Getting Started 9.2 Wiring 9.3 Writing a Program 9.4 Testing 10. Connecting to a Network 10.1 Connecting to a WiFi Hotspot 10.2 Building a Simple Web Server Source Code Contact
Preface This book was written to help anyone want to get started with NodeMCU v2 board development. It describes the basic elements of NodeMCU development starting with Lua programming. Agus Kurniawan Depok, July 2015
1. Preparing Development Environment
1.1 NodeMCU NodeMCU is an open source IoT platform. It uses the Lua scripting language. NodeMCU was created shortly after the ESP8266 came out. Further information, you can read it on http://nodemcu.com/index_en.html . The following is a form of NodeMCU v2.
You can buy this product on your local electronic store. The following is the list of Arduino store you can buy SeeedStudio, http://www.seeedstudio.com/ Amazon, http://www.amazon.com eBay, http://www.ebay.com Banggood, http://www.banggood.com/ DX, http://www.dx.com/
1.2 Electronics Components We need electronic components to build our testing, for instance, Resistor, LED, sensor devices and etc. I recommend you can buy electronic component kit. We can use electronics kit from Arduino to be developed on NodeMCU. The following is a list of electronics kit which can be used in our case.
1.2.1 Arduino Starter Kit Store website: http://arduino.cc/en/Main/ArduinoStarterKit
1.2.2 Fritzing Store website: http://shop.fritzing.org/ . You can buy Fritzing Starter Kit with Arduino UNO or Fritzing Starter Kit with Arduino Mega.
1.2.3 Cooking-Hacks: Arduino Starter Kit Store website: http://www.cooking-hacks.com/index.php/shop/arduino/starterkits/arduino-starter-kit.html
1.2.4 Arduino Sidekick Basic kit v2 Store website: http://www.seeedstudio.com/depot/Sidekick-Basic-Kit-for-Arduino-V2-p1858.html You also can find this kit on this online store. http://www.exp-tech.de/seeed-studio-sidekick-basic-kit-for-arduino-v2
1.2.5 Grove - Starter Kit for Arduino Another option, you can buy this kit on Seeedstudio, http://www.seeedstudio.com/depot/Grove-Starter-Kit-for-Arduino-p-1855.html .
1.2.6 DFRobot - Arduino Kit for Beginner v3 DFRobot provides Arduino kit too. You can buy it on the following website. http://www.dfrobot.com/index.php?route=product/product&path=35_49&product_id=345
1.3 Development Tools To develop app with NodeMCU target, we can use any editor. In this book, I use Arduino IDE for text editor. You can learn how to install it on chapter 2.
1.4 Testing For testing, I used NodeMCU v2 on Windows 8.1.
I also used Arduino Sidekick Basic kit for electronic components.
2. Setting Up NodeMCU
This chapter explains how to work on setting up NodeMCU board.
2.1 Getting Started In this chapter, we learn how to get started with NodeMCU board. We try to reflash the latest NodeMCU firmware and then test some basic scripts.
2.2 Connecting NodeMCU board to Computer Firstly, you connect NodeMCU board to PC via microUSB cable. After connected, you may get lighting on blue LED.
If you are working on Windows platform, open Device Manager, you should see NodeMCU board detected on Ports (COM & LPT).
However, if you get a problem about NodeMCU hardware driver, you update that driver. You also can install a driver from Silicon Labs because NodeMCU v2 uses this chip, from https://www.silabs.com/products/mcu/Pages/USBtoUARTBridgeVCPDrivers.aspx . Please download it based on your platform. For instance, you download the driver for mac. Just follow instructions.
After installed, you verify it. For instance, on my OS X it has detected. Type this command. ls /dev/cu*
For Linux, you can use ls /dev/tty* . Then, you see a list of driver. This board is recognized as /dev/cu.SLAB_USBtoUART .
Next up, on your computer, use a serial console program such as CoolTerm (Mac) or Putty (Windows) or screen (linux) to connect to NodeMCU board. For instance, I used PuTTY on Windows.
If success, you should get NodeMCU shell in Lua script. You may get a problem, shown in Figure below.
In this case, we must flash the latest NodeMCU firmware. I will explain it on the next section.
2.3 Flashing The Latest NodeMCU Firmware In this section, we try to flash the latest NodeMCU firmware. You can get the latest NodeMCU firmware on https://github.com/nodemcu/nodemcu-firmware . Download *.bin file. In this scenario, I try to flash NodeMCU firmware on Windows, OSX and Linux.
2.3.1 Windows Platform In this section, I show you how to flash it on Windows platform. To flash firmware, you can use NodeMCU flasher. Please download NodeMCU Flasher on https://github.com/nodemcu/nodemcu-flasher . There are two binary platforms, x86 and x64. Open the program so you get the dialog as below.
Select COM Port where NodeMCU was attached. Then, click Advanced tab. Select Baudrate 5700 and SPI Mode is DIO.
Click Config tab and select firmware file.
On Operation tab, you start by clicking Flash button.
If done, you will get a notification.
To test, you can use serial/UART tool and connect to NodeMCU board. Set NodeMCU serial port and set baudrate 9600. Then, connect to the board. If success, you should see NodeMCU shell.
Try to write a simple script print(“Hello NodeMCU”) so you will get a response.
2.3.2 Linux and OS X Platforms If you’re working on Linux or Mac, you can use esptool.py tool from https://github.com/nodemcu/nodemcu-firmware/tree/master/tools . Just follow the instruction. In this section, I show you how to flash NodeMCU using Flasher, Flash Download tool, from http://bbs.espressif.com/viewtopic.php?f=5&t=433 . This tool actually runs Windows platform. In this case, you need to install wine tool, https://www.winehq.org , to emulate for running on Linux or OS X. Firstly, install wine tool. You can type this command on Linux platform, for instance,
Ubuntu Linux. $ sudo add-apt-repository ppa:ubuntu-wine/ppa $ sudo apt-get update $ sudo apt-get install wine1.7
If you’re working with OS X, you can install it via brew $ brew install wine
Then, download the latest Flashing tool from Espressif on http://bbs.espressif.com/viewtopic.php?f=5&t=433 . To extract this file, you need unrar. For instance, you can install it via brew on OS X platform. $ brew install unrar
After extracted, navigate to flashing too. Then, run it via wine. $ wine flash_download_tool_v1.2_150512.exe
After running, wine directory has created. Navigate to dosdevices folder and create a symlink to your NodeMCU tty device. For instance, on OS X my NodeMCU has detected on /dev/tty.SLAB_USBtoUART so I map it to com1 . $ cd ~/.wine/dosdevices $ ln -s /dev/tty.SLAB_USBtoUART com1
You can close and run this tool. Now you can flash NodeMCU firmware for NodeMCU v2 with the following parameters; see green highlight. Set CrystalFreq 26M, FlASH SIZE 32Mbit, SPI SPEED 40MHz and SPI MODE DIO. Select COM Port to com1
If done, click START button. It will flash firmware to the board.
If done, you can test it using Serial/UART tool. Select serial port of NodeMCU and set baudrate 9600. Then, try to connect. If success, you should see Lua shell.
You can write simple program using print(). > print("Hello NodeMCU")
Shell will response this script.
2.4 Development Tools In this case, I show you several development tools you can use it in NodeMCU development.
2.4.1 Serial/UART Tool By default, you can use Serial/UART tools such as CoolTerm (Mac) or Putty (Windows) or screen (linux) .
You also can use Realterm, http://realterm.sourceforge.net/ and Tera Term, http://ttssh2.osdn.jp/index.html.en .
2.4.2 Arduino IDE If you have experience in Arduino development, you can use Arduino IDE to develop NodeMCU board too. You can use add-on on your Arduino using this library, https://github.com/esp8266/Arduino . Open Arduino IDE.
Then, click menu File -> Prefernces (Windows/Linux) or Arduino -> Preferences (OS X) so you should see Preferences dialog. Add http://arduino.esp8266.com/package_esp8266com_index.json on Additional Boards Manager URLs . If you have the list on there, just add ; for new list item,
If done, click OK button. Click menu Tools -> Board -> Boards Managers.
Then, you should see Boards Manager dialog. Find esp8266 board and install it.
After installed, you can see a list of ESP8266 Modules target on Arduino IDE.
Now you can write the program for NodeMCU.
2.4.3 NodeMCU Studio This tool is still development tool and written in C#. You may get problems while you are developing a program. You can download this tool on https://github.com/nodemcu/nodemcu-studio-csharp . We can wait the released version of this tool.
2.5 Hello NodeMCU: Blinking LED In this section, we build a blinking LED program via Lua shell. We use serial tool to write a program. Firstly, you must know NodeMCU GPIO. The following is NodeMCU v2 GPIO.
2.5.1 Wiring Connect LED on NodeMCU D1. Other LED pin is be connected to NodeMCU GND. Now you connect NodeMCU board to Computer via USB cable.
2.5.2 Writing Program Using Serial/UART Tool The first demo is to blink a LED. Type this script per lin on Serial/UART tool. -- hello.lua pin = 1 gpio.mode(pin,gpio.OUTPUT) gpio.write(pin,gpio.HIGH) print(gpio.read(pin)) gpio.write(pin,gpio.LOW)
This script will turn on a LED on D1 and then turn off it.
If you should see lighting LED after executed gpio.write(pin, gpio.HIGH).
Now we try to build a blinking LED. Type this script. -- blinking_led.lua
pin = 1 gpio.mode(pin,gpio.OUTPUT) while 1 do gpio.write(pin,gpio.HIGH) tmr.delay(1000000) gpio.write(pin,gpio.LOW) tmr.delay(1000000) end
You should see a blinking LED. If you want to stop, you can press RST button on NodeMCU board.
2.5.3 Uploading Lua Script File to NodeMCU Board In this section, I show you how to upload our Lua file to NodeMCU board and then execute it. We can use luatool from https://github.com/4refr0nt/luatool . This program uses Python to run the Lua file. Please install Python on your platform. luatool needs pyserial library to access UART on NodeMCU. You can install it via pip or easy_install sudo easy_install -U pyserial
Remove “sudo” if you’re working on Windows platform. Just run Command Prompt with Administrator level.
Now you can download this tool using wget or download it directly on Github website.
$ wget https://raw.githubusercontent.com/4refr0nt/luatool/master/luatool/luato $ wget https://raw.githubusercontent.com/4refr0nt/luatool/master/luatool/init. $ wget https://raw.githubusercontent.com/4refr0nt/luatool/master/luatool/main.
If your installed Python is python, then change code on the top of script, from this script. #!/usr/bin/env python2
to be the following script. #!/usr/bin/env python
Save this code. Now you can set access right on this file so you can execute it. $ sudo chmod a+x luatool.py
For testing, I use blinking led from section 2.5.2. Save that script into a file, called blinking_led.lua. Type this command to upload to NodeMCU board.
$ ./luatool.py --port /dev/cu.SLAB_USBtoUART --src blinking_led.lua --dest bli
Change —port parameter based on your attached NodeMCU board, for instance, COM5, /dev/ttyAM0.
If done, this file will be available on NodeMCU. To execute this file, connect to NodeMCU via serial tool and type this command. > dofile("blinking_led.lua")
If you want to upload and execute Lua script file, you can add —dofile parameter on your command. Type this command.
$ ./luatool.py --port /dev/cu.SLAB_USBtoUART --src blinking_led.lua --dest bli
This command will upload Lua file and then execute it. If you modified codes and upload the file again, you must press RST to make sure NodeMCU doesn’t keep your file. Sometimes you want your program run after NodeMCU restarts, you can write Lua file with named main.lua. This file will be executed by NodeMCU. Warning!! if your main.lua is error, you will get problem on NodeMCU.
3. Lua Programming Language
This chapter explains the basic of Lua programming language. If you already know about Lua programming, you can skip this chapter.
3.1 Preparing Development Environment To work with Lua development, we must install Lua compiler and its runtime. You can download it on http://www.lua.org based your platform. For OS X user, you can install it via brew. $ brew install lua
After installed, you can execute Lua and run some Lua syntax. $ lua > print("Hello Lua") > a = 5 + 8 > print(a)
If you want to quit from Lua shell, you can press CTRL+D keys.
3.2 Common Rule You can write Lua script without ending “;” at the end of syntax. Here is the syntax rule: syntax_code1 syntax_code2 syntax_code3
3.3 Variables In this section, we explore how to define a variable and assign its value.
3.3.1 Declaring Variable To declare a variable called city, m, and n you can write the following script: local city local m, n
Once declared, these variables can be used to store any type data.
3.3.2 Assigning Variables Variable that you already declare can be assigned by a value. It can done using the equals sign (=). For example, variable city will assign a string value “Berlin”, you would write this: city = "Berlin" m = 2 n = 5
We also can declare a variable and assign its value.
3.3.3 Demo For illustration for declaring variables using Lua, create a file, called basic.lua. Write the following script for basic.lua. -- this a simple script for Lua -- declare variables local city local m, n -- assignment city = "Berlin" m = 2 n = 5 -- declare and assign variables
a = 6 str = "Hello world" local p,q = 10, 12
print(city) print(m) print(n) print(a) print(str) print(p) print(q)
Save this file. Then, try to build and run it. $ lua basic.lua
A sample output can be seen in Figure below.
3.4 Comment You may explain how to work on your code with writing comments. To do it, you can use — syntax. Here is sample code: -- this a simple script for Lua -- declare variables local city local m, n
3.5 Arithmetic Operations Lua supports the same four basic arithmetic operations such as addition, subtraction, multiplication, and division. For testing, create a folder arithdemo. Then, create a file, called arithdemo.lua. The following is the code illustration for basic arithmetic in arithdemo.lua: -- basic arithmetic a = 3 b = 2.4 c = a + b d = a - b e = a / b f = a * b print(c) print(d) print(e) print(f)
Then, try to build and run it. The following is a sample output.
3.6 Mathematical Functions We try to work with math library. Create a file, called mathdemo.lua, and write this script. -- math demo a = 2.5 b = 1.6 c = math.pow(a,2) d = math.sin(a) e = math.cos(b) f = math.sqrt(a * b) g = math.pi
print(c) print(d) print(e) print(f) print(g)
Then, try to build and run it. The following is a sample output.
3.7 Increment and Decrement We can write a script for increment and decrement using Lua. increment a = a + 1 decrement. a = a - 1
Create a file, called incdec.lua and write this script. -- increment and decrement a = 4 print(a) -- increment a = a + 1 print(a) -- decrement a = a - 3 print(a)
Then, try to build and run it.
3.8 Comparison Operators You may determine equality or difference among variables or values. Here is the list of comparison operators: == is equal to ~= is not equal > is greater than < is less than >= is greater than or equal to <= is less than or equal to
This is sample code for comparison usage. -- comparison a = 3 b = 10 print(a < b) print(a > b) print(a <= b) print(a >= b) print(a == b) print(a ~= b)
Build and run it. A sample output of the program can be seen in Figure below.
3.9 Logical Operators These operators can be used to determine the logic between variables or values. and and or or not not
Sample code: -- logical operators a = 3 b = 4 print(a
1) print(a>b or a>4) print(a4))
Save this script into a file, called logical.lua. Build and run it. A sample output of the program can be seen in Figure below.
3.10 Decision - if..then Syntax model for if..then can be formulated as below: if conditional then -- do something else -- do something end
conditional can be obtained by logical or/and comparison operations. -- ifthen demo a = 3 if a>1 then print("a>1") b = 3 print(b) else print("a<1") b = 10 print(b) end
Now you can run it. A sample output of the program can be seen in Figure below.
3.11 Iteration - for Iteration operation is useful when we do repetitive activities. The following is for syntax. for initialization,end number,step do end
For testing, write this script into a file, fordemo.lua. for i=1,10,1 do print(i) end
Save this file and run it. A sample output of the program can be seen in Figure below.
3.12 Iteration - while Lua provides while syntax to do a looping. Write this script for testing. i = 1 while i < 10 do print(i) i = i + 1 end
Save this code into a file, called whiledemo.lua. Build and run it. A sample output of the program can be seen in Figure below.
3.13 Iteration - repeat Lua also provides repeat syntax to do looping. For a sample demo, type these scripts. n = 5 repeat print(n) n = n + 1 until n > 12
Save these scripts into a file, called repeatdemo.lua. Then, run this demo.
3.14 break and do break can be used to stop on the code point. We can use “do break end” to stop our looping. Write these scripts for testing. print("--break demo---") n = 1 while n < 10 do print(n) n = n + 1 if n == 7 then do break end end end
Save them into a file, called breakdo.lua and run it. A sample output of the program can be seen in Figure below.
3.15 Array Like other programming language, Lua provides array called Tables. We can define an array using {}. To get a length of array, we can use #variable_name. For testing, type these scripts. cities = {"tokyo", "new york", "london", "berlin"} numbers = {2, 4, 6, 8, 10,12} print(cities) print("length:",#cities) print(cities[3]) print("length numbers:",#numbers) print(numbers[5]) -- display all content of array print("--display array") for i=1, #cities do print(cities[i]) end
Save them into a file, called array.lua. Then, run it.
3.16 Functions A function can be used to save your redundant activities. We can define a function using (). It can attach parameters and return a value. Let’s write these scripts for testing. function foo() print("calling from foo()") end function add(a,b) return a + b end print("---function demo---") foo() c = add(10, 5) print(c)
Save into a file, called functiondemo.lua. Then, run it.
3.17 Lua Modules A module may consists of functions. It can save your development time due to reusable API. To build a module in Lua, we just create a Lua file and called it. For illustration, create a file, called simplemodule.lua and write these scripts. function add(a, b) return a + b end function compute(a, b, c) return a + b - c end
Then, we call simplemodule.lua on our code. Create a file, called loadmodule.lua and write these scripts. require("simplemodule") print("--load module--") res = add(10, 4) print(res) c = compute(5, 6, 8) print(c)
Save all files. Run our program on loadmodule.lua.
4. GPIO Programming
In this chapter I’m going to explain how to work with GPIO on NodeMCU and write a program.
4.1 Getting Started In general, GPIO can be used to control digital I/O on NodeMCU. We can use gpio.read() to read GPIO value and gpio.write() to write HIGH/LOW to GPIO pins. Firstly, we define our GPIO mode using gpio.mode(). It can be either GPIO output or GPIO input. A list of NodeMCU API can be read on this site, https://github.com/nodemcu/nodemcufirmware/wiki/nodemcu_api_en .
In this chapter, we build a program to illustrate how NodeMCU GPIO work. We need a LED and a pushbutton. Let’s start!.
4.2 Wiring Connect LED to D1 on Arduino and pushbutton to D2. The following is a sample of wiring.
4.3 Writing a Program To create a program, we just create a new Lua file, called gpiodemo.lua. Then, write these scripts. led = 1 pushbutton = 2 gpio.mode(led,gpio.OUTPUT) gpio.mode(pushbutton,gpio.INPUT) while 1 do state = gpio.read(pushbutton) if state==0 then gpio.write(led,gpio.LOW) else gpio.write(led,gpio.HIGH) end print(state) tmr.delay(1000000) end
Save these scripts.
4.4 Testing Now you can upload and run this program to NodeMCU board. For testing, try to press pushbutton. You should see a lighting LED.
You also see the program output if you connect to NodeMCU board via Serial app.
5. PWM and Analog Input
This chapter explains how to work with NodeMCU Analog I/O.
5.1 Getting Started NodeMCU board provides Analog I/O which can be connected to sensor or actuator devices. See the following of NodeMCU GPIO.
In this chapter, we try to access NodeMCU Analog I/O using Lua program. There are two scenarios for our cases: Controlling RGB LED Reading Analog input using Potentiometer
Let’s start.
5.2 Demo Analog Output (PWM) : RGB LED In this scenario we build a Lua program to control RGB LED color using NodeMCU Analog output (PWM). RGB LED has 4 pins that you can see it on Figure below.
To understand these pins, you can see the following Figure.
Note: Pin 1: Red Pin 2: Common pin
Pin 3: Green Pin 4: Blue
Now we can start to build a Lua application and hardware implementation.
5.2.1 Wiring For our testing, we configure the following PWM pins. RGB LED pin 1 (red) is connected to NodeMCU D1 RGB LED pin 2 is connected to NodeMCU 3V3 (VCC +3.3V) RGB LED pin 3 (green) is connected to NodeMCU D2 RGB LED pin 4 (blue) is connected to NodeMCU D3
Here is a sample implementation with NodeMCU and RGB Led
5.2.2 Writing Program To display a certain color, we must combine colors from red, green, blue. NodeMCU provides API for PWM which can set a value from 0 to 1023 using pwm.setup(). Based on NodeMCU Lua API, we only work with PWM maximum 3 PWM simultaneously. Let”s start to build a program. Firstly, create a file, called rgbdemo.lua. Then, write these scripts. red = 1
green = 2 blue = 3 function set_rgb(r, g, b) print(r,g,b) pwm.setup(red, 100, r) pwm.setup(green, 100, g) pwm.setup(blue, 100, b) pwm.start(red) pwm.start(green) pwm.start(blue) end function stop_all_pwm() pwm.stop(red) pwm.stop(green) pwm.stop(blue) end while 1 do print("red") set_rgb(0, 1023, 1023) tmr.delay(1000000) stop_all_pwm() print("green") set_rgb(1023, 0, 1023) tmr.delay(1000000) print("blue") set_rgb(1023, 1023, 0) tmr.delay(1000000) print("yellow") set_rgb(0, 0, 1023) tmr.delay(1000000) print("purple") set_rgb(700, 1023, 700) tmr.delay(1000000) print("aqua") set_rgb(1023, 0, 0) tmr.delay(1000000) end
This program will generate six colors: red, green, blue, yellow, purple, and aqua. Save this file.
5.2.3 Testing
Upload and run the program. You should see several color on RGB LED. The following is a sample demo on RGB LED.
If you connect to NodeMCU board via Serial app, you should get program output, shown in Figure below.
5.3 Demo Analog Input: Working with Potentiometer In this section, we learn how to read analog input on NodeMCU board. For illustration, I use Potentiometer as analog input source. Our scenario is to read analog value from Potentiometer. Then, display it on Lua shell. NodeMCU v2 only has one ADC on A0. If you want to work with many analog input, you must expand it using ICs based ADC. In this section, we are working on NodeMCU ADC on A0. Let’s start!.
5.3.1 Wiring To understand Potentiometer, you see its scheme in Figure below.
You can connect VCC to NodeMCU board on 3V3 pin (VCC +3.3V). Vout to NodeMCU board Analog input A0. In addition, GND to NodeMCU board GND. The following is hardware implementation. I use slide potentiometer.
5.3.2 Writing Program Firstly, create a file, called adcdemo.lua. To read analog input, we can use adc.read() function. Ok, Let’s write these scripts. print("ADC demo") while 1 do print("reading…") val = adc.read(0) print("Analog: ",val) tmr.delay(1000000) end
Save this code.
5.3.3 Testing Upload and run this program. If success, you can see analog value on Serial app.
6. Working with I2C
In this chapter we learn how to work with I2C on NodeMCU board using Lua script.
6.1 Getting Started The I2C (Inter-Integrated Circuit) bus was designed by Philips in the early ’80s to allow easy communication between components which reside on the same circuit board. TWI stands for Two Wire Interface and for most marts this bus is identical to I²C. The name TWI was introduced by Atmel and other companies to avoid conflicts with trademark issues related to I²C. I2C bus consists of two wires, SDA (Serial Data Line) and SCL (Serial Clock Line). NodeMCU v2 has I2C/TWI on SD0 (SDA), SD1 (SDA), SD2 (SDA), SD3 (SDA) and CLK (SCL).
For testing, I used PCF8591 AD/DA Converter module with sensor and actuator devices. You can find it on the following online store: Amazon, http://www.amazon.com/PCF8591-Converter-Module-DigitalConversion/dp/B00BXX4UWC/ eBay, http://www.ebay.com Dealextreme, http://www.dx.com/p/pcf8591-ad-da-analog-to-digital-digital-toanalog-converter-module-w-dupont-cable-deep-blue-336384 Aliexpress, http://www.aliexpress.com/
In addition, you can find this device on your local electronics store/online store.
This module has mini form model too, for instance, you can find it on Amazon, http://www.amazon.com/WaveShare-PCF8591T-Converter-EvaluationDevelopment/dp/B00KM6X2OI/ .
This module use PCF8591 IC and you can read the datasheet on the following URLs. http://www.electrodragon.com/w/images/e/ed/PCF8591.pdf http://www.nxp.com/documents/data_sheet/PCF8591.pdf
I usually use this module to test I2C but NodeMCU v2 firmware doesn’t support with I2C address 0x90. Basically you can modify firmware code and then built it. In this chapter, we build a program to access sensor via I2C using Lua script and use Arduino as I2C slave. We can use any pin on NodeMCU GPIO for I2C using I2c library from NodeMCU firmware.
6.2 Writing Program We use Arduino Uno as I2C source. You can connect Arduino Uno to NodeMCU board directly. The following is our wiring lab: Arduino Uno SDA (A4) —> NodeMCU SDA (D1) Arduino Uno SCL (A5) —> NodeMCU CLK (D2) Arduino Uno GND —> NodeMCU GND
Hardware implementation can be shown in Figure below.
6.3 Writing Program The first step is to write Arduino program. We can use Wire library to interact with I2C. In this case, our Arduino acts as I2C slave and sends random byte. Open Arduino IDE and write this code. #include const byte SLAVE_ADDRESS = 0x15; int led = 13; byte x; // source: // http://forum.arduino.cc/index.php?topic=197633.0 byte randomDigit() { unsigned long t = micros(); byte r = (t % 10) + 1; for (byte i = 1; i <= 4; i++) { t /= 10; r *= ((t % 10) + 1); r %= 11; } return (r - 1); } void sendData(){ byte data = randomDigit(); data = data + 30; Wire.write(data); Serial.println(data); }
void setup() { pinMode(led, OUTPUT); Serial.begin(9600); Wire.begin(SLAVE_ADDRESS); TWBR = 152; // 50 kHz speed Wire.onRequest(sendData); } void loop() { delay(500); }
Save this code. Compile and upload this program to Arduino board. Now you can start to write a Lua program for NodeMCU. Create a file, called i2cdemo.lua and write these scripts. id=0 sda=1 scl=2 ARDUINO_I2C = 0x15
i2c.setup(id,sda,scl,i2c.SLOW) function read_data(id,dev_addr)
i2c.start(id) i2c.address(id, dev_addr,i2c.RECEIVER) c = i2c.read(id,1) c = i2c.read(id,1) i2c.stop(id) return c end print("I2C demo") while 1 do val = read_data(id, ARDUINO_I2C) print("RCV: ",string.byte(val)) tmr.delay(1000000) end
Save this code.
6.4 Testing Now you can upload and run the Lua program to NodeMCU board. If success, open Serial app and connect to NodeMCU to see the program output from Lua shell. The following is a sample output.
You also can see the Arduino output using Serial Monitor.
7. UART
In this chapter I’m going to explain how to access UART on NodeMCU board.
7.1 Getting Started NodeMCU v2 provides two UART but we only able to use one UART.
You can read Lua API to access NodeMCU UART on https://github.com/nodemcu/nodemcu-firmware/wiki/nodemcu_api_en . The following is Lua API for UART: uart.setup() . To setup UART such as baud, databits, parity, stopbits, echo. uart.on(). To listen incoming messages from UART uart.write(). To write data into UART
In this chapter, I use Arduino board as UART source. We read incoming message from UART. Let’s start!.
7.2 Wiring In this scenario, I use Arduino Uno which is connected to NodeMCU board. The following is our wiring. NodeMCU D10 (TXD0) is connected to Arduino Digital 10 NodeMCU D9 (RCD0) is connected to Arduino Digital 11 NodeMCU GND is connected to Arduino GND
My wiring implementation can be seen in Figure below.
7.3 Writing a Program Firstly, we write a program for Arduino using Arduino IDE. We use SoftwareSerial to access Serial on Digital 10 and 11. This program will wait incoming UART data and then send to Arduino UART on 0 and 1 pins. Write this program. #include SoftwareSerial mySerial(10, 11); // RX, TX void setup() { Serial.begin(9600); mySerial.begin(9600); } void loop() { if (mySerial.available() > 0) { Serial.write(mySerial.read()); } }
Save this program. Then, upload it to Arduino board. Before uploading, please make sure Arduino UART (digital 0, 1, 10, and 11 pins) doesn’t connect to any board. The next step is to write a program for NodeMCU board. Create a file, called uartdemo.lua. Write these scripts. uart.setup(0, 9600, 8, 0, 1, 0) val = 65 -- looping while 1 do uart.write(0,string.char(val),"\r\n") val = val + 1
if val>90 then val = 65 end tmr.delay(1000000) end
Save this file.
7.4 Testing Now you can upload and run Lua program. Don’t connect NodeMCU UART to Arduino while uploading a program. If done, connect NodeMCU UART to Arduino UART (Digital pins: 10 and 11). To see the UART output, open Serial Monitor tool from Arduino IDE. Set baud 9600 and No line ending. You should see the UART output.
8. SPI
In this chapter I’m going to explain how to work with SPI on NodeMCU board.
8.1 Getting Started The Serial Peripheral Interface (SPI) is a communication bus that is used to interface one or more slave peripheral integrated circuits (ICs) to a single master SPI device; usually a microcontroller or microprocessor of some sort. SPI in NodeMCU board can be defined on the following pins: MOSI MISO SCK
You can see these pins on S NodeMCU board, shown in Figure below.
We can only use one SPI on NodeMCU board with SPI master mode. If we’re working on SPI, we can’t access UART on the board. In this chapter, I use Arduino board as SPI slave. Let’s start!.
8.2 Wiring To work both SPI and UART/USB, we don’t connect MISO pin. For testing, I use Arduino board. Do wiring as follows. NodeMCU MOSI (SD1) pin is connected to Arduino MOSI (Digital 11) pin NodeMCU SCLK (CLK) pin is connected to Arduino SCK (Digital 13) pin NodeMCU GND pin is connected to Arduino GND pin NodeMCU CS (CMD) pin is connected to Arduino SS (Digital 10) pin
The following is a sample of wiring.
8.3 Writing a Program Firstly, we write a program for Arduino. Write these codes on Arduino IDE. #include char buf; volatile byte pos; volatile boolean isAvailable; void setup() { Serial.begin (9600); // for debugging // SPI slave mode SPCR |= bit (SPE); SPCR |= _BV(SPIE); isAvailable = false; pos = 0; pinMode(MISO, OUTPUT); SPI.attachInterrupt(); } ISR (SPI_STC_vect) { byte c = SPDR; if(c>64 && c<91){ buf = c; isAvailable = true; } } void loop() { if(isAvailable){ Serial.println (buf); isAvailable = false; } }
This program does wait incoming data from SPI master and then display the received data to Arduino Serial so we can see it on Serial Monitor.
Save this program as Arduino_spi. Build and upload the program to Arduino board. The next step is to write a program for NodeMCU. Create a file, called spidemo.lua, and write these scripts. spi.setup(1, spi.MASTER, spi.CPOL_LOW, spi.CPHA_LOW, spi.DATABITS_8, 0) val = 65 while 1 do spi.send(1,string.char(val)) print(string.char(val)) val = val + 1 if val>90 then val = 65 end
tmr.delay(1000000) end
This program will send data ASCII from 65 to 90. Save this code.
8.4 Testing Now you can upload Lua program to NodeMCU board. If done, open Serial Monitor tool from Arduino. You should see received data from SPI.
If you connect to NodeMCU board via Serial tool, you should see the program output too.
9. Working with OLED Display
In this chapter I’m going to explain how to work with OLED display
9.1 Getting Started We can display characters, numbers or symbols using an OLED graphic display module. An organic light-emitting diode (OLED) is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of organic compound which emits light in response to an electric current [source: http://en.wikipedia.org/wiki/OLED]. In this chapter, we work with OLED display 128x64 with I2C interface which display characters.
Let’s start!.
9.2 Wiring The following is our wiring: NodeMCU SDA (D1) to OLED SDA NodeMCU SCL (D2) to OLED SCL NodeMCU VCC +3.3V to OLED VCC NodeMCU GND to OLED GND
The following is a sample of wiring.
9.3 Writing a Program For testing, we use a sample program from https://github.com/nodemcu/nodemcufirmware/blob/master/lua_examples/u8glib/u8g_graphics_test.lua . With activating OLED with I2C interface. Create a file, called oleddemo.lua, and write this code. function init_i2c_display() -- SDA and SCL can be assigned freely to available GPIOs local sda = 1 -- GPIO05 (D1) local scl = 2 -- GPIO04 (D2) local sla = 0x3c i2c.setup(0, sda, scl, i2c.SLOW) disp = u8g.ssd1306_128x64_i2c(sla) end -- graphic test components function prepare() disp:setFont(u8g.font_6x10) disp:setFontRefHeightExtendedText() disp:setDefaultForegroundColor() disp:setFontPosTop() end function box_frame(a) disp:drawStr(0, 0, "drawBox") disp:drawBox(5, 10, 20, 10) disp:drawBox(10+a, 15, 30, 7) disp:drawStr(0, 30, "drawFrame") disp:drawFrame(5, 10+30, 20, 10) disp:drawFrame(10+a, 15+30, 30, 7) end function disc_circle(a) disp:drawStr(0, 0, "drawDisc") disp:drawDisc(10, 18, 9) disp:drawDisc(24+a, 16, 7) disp:drawStr(0, 30, "drawCircle") disp:drawCircle(10, 18+30, 9) disp:drawCircle(24+a, 16+30, 7) end function r_frame(a) disp:drawStr(0, 0, "drawRFrame/Box") disp:drawRFrame(5, 10, 40, 30, a+1) disp:drawRBox(50, 10, 25, 40, a+1) end function stringtest(a) disp:drawStr(30+a, 31, " 0") disp:drawStr90(30, 31+a, " 90")
disp:drawStr180(30-a, 31, " 180") disp:drawStr270(30, 31-a, " 270") end function line(a) disp:drawStr(0, 0, "drawLine") disp:drawLine(7+a, 10, 40, 55) disp:drawLine(7+a*2, 10, 60, 55) disp:drawLine(7+a*3, 10, 80, 55) disp:drawLine(7+a*4, 10, 100, 55) end function triangle(a) local offset = a disp:drawStr(0, 0, "drawTriangle") disp:drawTriangle(14,7, 45,30, 10,40) disp:drawTriangle(14+offset,7-offset, 45+offset,30-offset, 57+offset, disp:drawTriangle(57+offset*2,10, 45+offset*2,30, 86+offset*2,53) disp:drawTriangle(10+offset,40+offset, 45+offset,30+offset, 86+offset, end function ascii_1() local x, y, s disp:drawStr(0, 0, "ASCII page 1") for y = 0, 5, 1 do for x = 0, 15, 1 do s = y*16 + x + 32 disp:drawStr(x*7, y*10+10, string.char(s)) end end end function extra_page(a) disp:drawStr(0, 12, "setScale2x2") disp:setScale2x2() disp:drawStr(0, 6+a, "setScale2x2") disp:undoScale() end
-- the draw() routine function draw(draw_state) local component = bit.rshift(draw_state, 3) prepare() if (component == 0) then box_frame(bit.band(draw_state, 7)) elseif (component == 1) then disc_circle(bit.band(draw_state, 7)) elseif (component == 2) then r_frame(bit.band(draw_state, 7)) elseif (component == 3) then
stringtest(bit.band(draw_state, 7)) elseif (component == 4) then line(bit.band(draw_state, 7)) elseif (component == 5) then triangle(bit.band(draw_state, 7)) elseif (component == 6) then ascii_1() elseif (component == 7) then extra_page(bit.band(draw_state, 7)) end end function graphics_test(delay) print("--- Starting Graphics Test ---") -- cycle through all components local draw_state for draw_state = 0, 7 + 8*8, 1 do disp:firstPage() repeat draw(draw_state) until disp:nextPage() == false --print(node.heap()) tmr.delay(delay) -- re-trigger Watchdog! tmr.wdclr() end print("--- Graphics Test done ---") end init_i2c_display() graphics_test(50000)
Save this code.
9.4 Testing Now you can compile and run this program into NodeMCU board. You should see OLED displays some characters, symbols and graphics.
10. Connecting to a Network
In this chapter I’m going to explain how to connect a network from NodeMCU.
10.1 Connecting to a WiFi Hotspot We can wifi object to work with WiFi module on NodeMCU. For instance, we connect a SSID with a pin password. Write this code. -- connect a WIFI network wifi.setmode(wifi.STATION) wifi.sta.config("SSID","password") print("connecting…") wifi.sta.connect() ip = wifi.sta.getip() print("IP: ",ip)
Change SSID and password values. Save this code into a file called network.lua. Upload this program. Then, run it via Serial program so you can see NodeMCU’s IP Address.
10.2 Building a Simple Web Server The second demo is to build a simple web server. Write this code. wifi.setmode(wifi.STATION) wifi.sta.config("SSID","password") print("connecting…") wifi.sta.connect() ip = wifi.sta.getip() print("IP: ",ip)
srv = net.createServer(net.TCP) srv:listen(80, function(conn) conn:on("receive",function(conn,payload) print(payload) conn:send("HTTP/1.1 200/OK\r\nServer: NodeMCU\r\nContent-Type: text/html conn:send("NodeMCUHello, NodeMc end) conn:on("sent",function(conn) conn:close() end) end)
Change SSID and password values. Save this code into a file called webserver.lua. Upload this program. Then, run it via Serial program so you can see NodeMCU’s IP Address. Open a browser and navigate to IP address of NodeMCU.
The following is the program output on Serial app.
Source Code
You can download source code on http://www.aguskurniawan.net/book/nodemcu_11301082015.zip .
Contact
If you have question related to this book, please contact me at [email protected] . My blog: http://blog.aguskurniawan.net
