Controlling an RGB led using a Wemos Mini

In this example we will connect an RGB led to a Wemos Mini, we will then create an example web page that will display buttons to switch on and off the various individual leds of an RGB led.

Our code example is based on a common cathode RGB led type, if you have a common anode type t hen you would have to invert the code, for example a high from an output would switch an led off and a low would switch it on.

Lets look at the Wemos MIni

Here is a picture I took of one alongside an Arduino Nano

DSCN2718

As you can see its nice and compact for any projects where space is an issue. Another great feature for ease of development is the ability to use the Arduino IDE or NodeMCU. this means you can get up and running quickly. The pin headers are located in a sensible layout, so it looks easy to create your own basic shields for the board

Lets look at some basic specs, the operating voltage and the input voltage to Analog are critical, remember this is a 3.3v board

Microcontroller ESP-8266EX
Operating Voltage 3.3V
Digital I/O Pins 11
Analog Input Pins 1(Max input: 3.2V)
Clock Speed 80MHz/160MHz
Flash 4M bytes

Here are the pin functions

Pin Function ESP-8266 Pin
TX TXD TXD
RX RXD RXD
A0 Analog input, max 3.3V input A0
D0 IO GPIO16
D1 IO, SCL GPIO5
D2 IO, SDA GPIO4
D3 IO, 10k Pull-up GPIO0
D4 IO, 10k Pull-up, BUILTIN_LED GPIO2
D5 IO, SCK GPIO14
D6 IO, MISO GPIO12
D7 IO, MOSI GPIO13
D8 IO, 10k Pull-down, SS GPIO15
G Ground GND
5V 5V –
3V3 3.3V 3.3V
RST Reset RST

So to summarise, the Wemos D1 mini has

  • 11 digital input/output pins, all pins have interrupt/pwm/I2C/one-wire supported(except D0)
  • 1 analog input(3.2V max input)
  • a Micro USB connection
  • Compatible with Arduino
  • Compatible with nodemcu

 

Now back to the RGB led controlled via a web page example

Parts List

Label Part Type Properties
LED1 RGB LED (com. cathode, rgb) rgb RGB; package 5 mm [THT]; polarity common cathode; pin order rgb
R1 1kΩ Resistor resistance 1kΩ; pin spacing 400 mil; bands 4; package THT; tolerance ±5%
R2 1kΩ Resistor resistance 1kΩ; pin spacing 400 mil; bands 4; package THT; tolerance ±5%
R3 1kΩ Resistor resistance 1kΩ; pin spacing 400 mil; bands 4; package THT; tolerance ±5%
WeMos D1 Mini1 WeMos D1 Mini headers female above; variant variant 1; cpu ESP-8266EX

Schematics

Here is a schematic and layout showing the required connection for the Wemos MIni and RGB led

 

wemos rgbled_bb

 

wemos rgbled_schem

 

Code

[codesyntax lang=”cpp”]

#include <ESP8266WiFi.h>
 
const char* ssid = "iainhendry";
const char* password = "iain061271";
 
int redPin = D5;
int greenPin = D6;
int bluePin = D7;

WiFiServer server(80);
 
void setup() 
{
  Serial.begin(115200);
  delay(10);
 
  //set up LEDs
  pinMode(redPin, OUTPUT);
  digitalWrite(redPin, LOW);
  pinMode(greenPin, OUTPUT);
  digitalWrite(greenPin, LOW);
  pinMode(bluePin, OUTPUT);
  digitalWrite(bluePin, LOW);
  
  // Connect to WiFi network
  Serial.print("Connecting to ");
  Serial.println(ssid);
   
  WiFi.begin(ssid, password);
   
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("WiFi connected");
   
  // Start the server
  server.begin();
  Serial.println("Server started");
 
  // Print the IP address
  Serial.print("Use this URL : ");
  Serial.print("http://");
  Serial.print(WiFi.localIP());
  Serial.println("/");
    
}
 
void loop() {
  // Check if a client has connected
  WiFiClient client = server.available();
  if (!client) {
    return;
  }
   
  // Wait until the client sends some data
  Serial.println("new client");
  while(!client.available()){
    delay(1);
  }
   
  // Read the first line of the request
  String request = client.readStringUntil('\r');
  Serial.println(request);
  client.flush();
   
  // Match the request
  int redvalue = LOW;
  if (request.indexOf("/REDLED=ON") != -1) {
    digitalWrite(redPin, HIGH);
    redvalue = HIGH;
  } 
  if (request.indexOf("/REDLED=OFF") != -1){
    digitalWrite(redPin, LOW);
    redvalue = LOW;
  }

  int greenvalue = LOW;
  if (request.indexOf("/GREENLED=ON") != -1) {
    digitalWrite(greenPin, HIGH);
    greenvalue = HIGH;
  } 
  if (request.indexOf("/GREENLED=OFF") != -1){
    digitalWrite(greenPin, LOW);
    greenvalue = LOW;
  }

  int bluevalue = LOW;
  if (request.indexOf("/BLUELED=ON") != -1) {
    digitalWrite(bluePin, HIGH);
    bluevalue = HIGH;
  } 
  if (request.indexOf("/BLUELED=OFF") != -1){
    digitalWrite(bluePin, LOW);
    bluevalue = LOW;
  }
   
 
  // Return the response
  client.println("HTTP/1.1 200 OK");
  client.println("Content-Type: text/html");
  client.println(""); //  do not forget this one
  client.println("<!DOCTYPE HTML>");
  client.println("<html>");
   
  client.print("Red led pin is now: ");
  if(redvalue == HIGH) {
    client.print(" On");  
  } else {
    client.print(" Off");
  }
  client.println("<br>");
  
  client.print("Green led pin is now: ");   
  if(greenvalue == HIGH) {
    client.print(" On");  
  } else {
    client.print(" Off");
  }
  client.println("<br>");
  
  client.print("Blue led pin is now: ");  
  if(bluevalue == HIGH) {
    client.print(" On");  
  } else {
    client.print(" Off");
  }
  client.println("<br>");
  
  client.println("<table>");
  client.println("<tr><td>");
  client.println("<a href=\"/REDLED=ON\"><input type=\"button\" value=\"RED LED ON\"></a><br>");
  client.println("</td><td>");
  client.println("<a href=\"/REDLED=OFF\"><input type=\"button\" value=\"RED LED OFF\"></a><br>");
  client.println("</td></tr>");
  client.println("<tr><td>");
  client.println("<a href=\"/GREENLED=ON\"><input type=\"button\" value=\"GREEN LED ON\"></a><br>");
  client.println("</td><td>");
  client.println("<a href=\"/GREENLED=OFF\"><input type=\"button\" value=\"GREEN LED OFF\"></a><br>");
  client.println("</td></tr>");
  client.println("<tr><td>");
  client.println("<a href=\"/BLUELED=ON\"><input type=\"button\" value=\"BLUE LED ON\"></a><br>");
  client.println("</td><td>");
  client.println("<a href=\"/BLUELED=OFF\"><input type=\"button\" value=\"BLUE LED OFF\"></a><br>");
  client.println("</td></tr>");
  client.println("</table>");
  client.println("</html>");
 
  delay(1);
  Serial.println("Client disconnected");
  Serial.println("");
 
}

[/codesyntax]

 

Testing

navigate to the web page and click on the buttons, you can open the serial monitor to verify the IP address.

 

Links

You can pick up one of these from about $5
D1 mini – Mini NodeMcu 4M bytes Lua WIFI Internet of Things development board based ESP8266 by WeMos

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