Making Things Talk

136 MAKING THINGS TALK

void lookForData() {

// wait for bytes from server:

if (Serial.available()) {

inByte = Serial.read();

// If you get a "<", what follows is the air quality index.

// You need to read what follows the <.

if (inByte == '<') {

stringPos = 0;

status = reading;

}

}

}

The stuff you see at the top is the

HTTP header. When you call the PHP

script from a browser, you don’t see

all of the header, because the browser

strips it out for you. The lookForData()

method reads strip the header out by

ignoring all the bytes before the < sign:

8

void readData() {

if (Serial.available()) {

inByte = Serial.read();

// Keep reading until you get a ">":

if (inByte != '>') {

// save only ASCII numeric characters (ASCII 0 - 9):

if ((inByte >= '0') && (inByte <= '9')){

inString[stringPos] = inByte;

stringPos++;

}

}

// if you get a ">", you've reached the end of the AQI reading:

else {

interpretResults();

}

}

}

After you get the < sign, the

readData() method takes only the

numeric characters from the remaining

string and saves them to the inString[]

array. When it gets the > symbol indi-

cating the end of the string, it calls the

interpretResults() method:

8

void interpretResults() {

// convert the string to a numeric value:

int airQuality = atoi(inString);

// set the meter appropriately:

setMeter(ai