I was able to get the Spark Core to upload data to Thingspeak after looking at some of the examples for using the arduino with the Wifi shield. a few things to note, I needed to put a slight delay after the stream or the spark would close the TCP connection too quickly. 100 ms seemed to do the trick. Also while my example has a delay to keep updates to Thingspeak I suggest using timers because over time the delay (which is blocking) will kill the Spark Cloud connection.
I set up a Sin wav as fake sensor data just to make a cool looking chart. I also setup an inverse of it to demo two streams. Below is the output chart and the example code.
#include "math.h"
// Thinkspeak channel information
String writeAPIKey = "<<Enter your channel's API key here>>";
String channelID = "<<Enter your channel's ID here>>";
// TCP socket initialize
TCPClient client;
float x;
float y;
/*--------------------------------------------------------
Setup
--------------------------------------------------------*/
void setup()
{
Serial.begin(9600);
delay(10000);
Serial.println("===Starting===");
}
/*--------------------------------------------------------
Main loop
--------------------------------------------------------*/
void loop()
{
if(Spark.connected())
{
for (float z = 4.712; z < 10.995; z = z + .15) // "z" sets the sin wave to the first zero crossing 4.712 and ends it on the next 10.995.
{
x = sin(z) * 127.5 + 127.5; // Making the sin wave all positive numbers and setting it to a scale of 0-255 (makes it easy to PWM an LED)
y = 255 - (sin(z) * 127.5 + 127.5); // This inverts the sin wave so we have two streams.
// Must convert data to Strings, make sure you use capital "S" in Strings
ThingSpeakUpdate("field1="+String(x)+"&field2="+String(y));
// I put this delay in place so we don't flood Thingspeak but you should really use a timer, delays screw with the sparkcloud connection some times.
delay(15000);
}
}
}
/*------------------------------------------------
Sends sensor data to Thingspeak
Inputs: String, data to be entered for each field
Returns:
------------------------------------------------*/
void ThingSpeakUpdate(String tsData)
{
Serial.println("Date string: " + tsData);
Serial.println("...Connecting to Thingspeak");
// Connecting and sending data to Thingspeak
if(client.connect("api.thingspeak.com", 80))
{
Serial.println("...Connection succesful, updating datastreams");
client.print("POST /update HTTP/1.1\n");
client.print("Host: api.thingspeak.com\n");
client.print("Connection: close\n");
client.print("X-THINGSPEAKAPIKEY: "+writeAPIKey+"\n");
client.print("Content-Type: application/x-www-form-urlencoded\n");
client.print("Content-Length: ");
client.print(tsData.length());
client.print("\n\n");
client.println(tsData); //the ""ln" is important here.
// This delay is pivitol without it the TCP client will often close before the data is fully sent
delay(200);
Serial.println("Thingspeak update sent.");
}
else{
// Failed to connect to Thingspeak
Serial.println("Unable to connect to Thingspeak.");
}
if(!client.connected()){
client.stop();
}
client.flush();
client.stop();
}
