Introduction: RGB With SparkCore and Curl

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Controlling a common RGB-LED with a Spark core and curl.

The complete code is attached.

Step 1: Parts and Wiring

To light up a simple rgb-LED you need:

  • 1 Spark.io Spark Core
  • 1 rgb-LED
  • 3 220-Ω resistors
  • 1 jumper
  • 1 breadboard

Please wire all parts according to the scheme.

Step 2: Code

Hook up the core and claim it.

Transfer the code via the Spark core IDE.

This is the core part of the code parsing a list of numeric arguments separated by ',' into an array of double values:

for(int i=0;i<=length;i++)// parse all parts of args between the separators {
	
	if(args.charAt(i)==separator || i == length){
	String substring = args.substring(from, i);
	int bufSize = 1+ substring.length();
	char buffer[bufSize];
	substring.toCharArray(buffer, bufSize);
	double value = atof(buffer);


	*(allValues + allValuesCount)=value;
	allValuesCount++;


	if(i < length) // next substring beyond separator
	from = i+1;
	}
}

Attachments

Step 3: Command

The call on a terminal-application for a yellow LED would be:

curl https://api.spark.io/v1/devices/0123456789abcdef01234567/changeColor \ -d "access_token=1234123412341234123412341234123412341234"\ -d "args=255,255,0”

Of course, the device-ID and the access-token have to be taken from the device you are working on.