This post describes how to control a remote LED using Arduino and Android. Nowadays a new emerging technology is Internet of Things (IoT): in other words all the physical objects (things) are connected together using internet infrastructure. Arduino is one of the most important object in this ecosystem. In this post, we will explore how to integrate Android with Arduino making a first step in IoT.Even Google at io15 presented its new IoT infrastructure called Brillo.
As said, we want to control a remote Led connected to Arduino Uno using an Android smartphone.
IoT Overview
The picture below shows the main objects involved in the IoT project:
What we need is:
- Arduino Uno
- Ethernet shield
- Smartphone with Android
Arduino: Web Server And Connections
#include <spi.h>
#include <ethernet.h>
byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
IPAddress ip(192, 168, 1, 130); // Arduino IP Add
EthernetServer server(80); // Web server
// Http data
String reqData; // Request from Smartphone
String header;
int contentSize = -1;
String CONTENT_LENGTH_TXT = "Content-Length: ";
void setup() {
// put your setup code here, to run once:
Serial.begin(9600);
pinMode(3, OUTPUT); // Set Pin 3 to OUTPUT Mode
Serial.print("Ready...");
//
Ethernet.begin(mac, ip);
server.begin();
}
void loop() {
EthernetClient client = server.available(); // Is there a client (Our Android smartphone)
if (client) {
// Let's start reading
boolean isLastLine = true;
boolean isBody = false;
header = "";
reqData = "";
int contentLen = 0;
Serial.print("Client connected!");
while (client.connected()) {
if (client.available()) {
// Read data
char c = client.read();
// Serial.print(c);
if (contentSize == contentLen) {
// Serial.println("Body ["+reqData+"]");
int idx = reqData.indexOf(":");
String status = reqData.substring(idx + 1, idx + 2);
Serial.println("Status : " + status);
if (status.equals("1")) {
digitalWrite(3, HIGH);
}
else {
digitalWrite(3, LOW);
}
client.println("HTTP/1.1 200 OK");
client.println("Content-Type: text/html");
client.println("Connection: close");
client.println();
// send web page
client.println("");
client.println("");
delay(1);
break;
}
if (c == '\n' && isLastLine) {
isBody = true;
int pos = header.indexOf(CONTENT_LENGTH_TXT);
String tmp = header.substring(pos, header.length());
//Serial.println("Tmp ["+tmp+"]");
int pos1 = tmp.indexOf("\r\n");
String size = tmp.substring(CONTENT_LENGTH_TXT.length(), pos1);
Serial.println("Size ["+size+"]");
contentSize = size.toInt();
}
if (isBody) {
reqData += c;
contentLen++;
}
else {
header += c;
}
if (c == '\n' ) {
isLastLine = true;
}
else if (c != '\r' ) {
isLastLine = false;
}
}
}
// Close connection
Serial.println("Stop..");
client.stop();
}
}Almost all the arduino source code is used to handle HTTP connection. Notice that at line 3 we set the MAC Address of the ethernet shield, while at line 4 we set the IP address.
Android Client: Send HTTP Request
On the Android side the things are much more simpler; the Android UI is shown below:
There is one simple button, when the user clicks on it, the app sends an HTTP request to Arduino.
The app layout is very simple and it is not covered here, the core of the app is where the button click is handled:
ledView = (ImageView) findViewById(R.id.ledImg);
// Set default image
ledView.setImageResource(R.drawable.white_circle);
// Init HTTP client
client = new HttpClient();
ledView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
client.doRrequest(status ? "1" : "0");
status = !status;
if (status)
ledView.setImageResource(R.drawable.white_circle);
else
ledView.setImageResource(R.drawable.red_circle);
}
});When the user touches the button, the app sends an HTTP request using HTTP client. In this case, this project uses OkHttp. The HTTP client is very simple:
public void doRrequest(String status) {
initClient();
Log.d("AA", "Making request..["+status+"]");
Request req = new Request.Builder()
.url(URL)
.post(RequestBody.create(JSON, createJSON(status)))
.build();
client.newCall(req).enqueue(new Callback() {
@Override
public void onFailure(Request request, IOException e) { }
@Override
public void onResponse(Response response) throws IOException {
Log.d("AA", "resp [" + response.body().string() + "]");
}
});
}Below are some images of my work:
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