Making Things Talk

256 MAKING THINGS TALK

Continued from previous page.

// read <numSamples> 10-bit analog values, two at a time

// because each reading is two bytes long:

for (int i = 0; i < numSamples * 2; i=i+2) {

// 10-bit value = high byte * 256 + low byte:

int thisSample = (thisPacket[i + adcStart] * 256) +

thisPacket[(i + 1) + adcStart];

// put the result in one of 5 bytes:

adcValues[i/2] = thisSample;

// add the result to the total for averaging later:

total = total + thisSample;

}

// average the result:

int average = total / numSamples;

print("Average reading:" + average + "\t");

// print the received signal strength:

println("Signal Strength:" + rssi);

}

Now that you’ve got the average

reading printing out, add some code to

graph the result. For this, you’ll need a

new global variable before the setup()

method that keeps track of where you

are horizontally on the graph:

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int hPos = 0; // horizontal position on the graph

Now add a new method,

drawGraph(), to the end of the

program:

Call this from the parseData() method,

replacing the println() statement that

prints out the average, as well as the

println() statement that prints out the

signal strength (rssi), like so:

// draw a line on the graph:

drawGraph(average/4);

Now when you run the program, it

should draw a graph of the sensor

readings, updating every time it gets

a new datagram.

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