The following web interface was created using javascript plugins on a ThingSpeak channel page to control a LED and monitor the state of digital and analog inputs on a Spark Core using Spark.variable() and the Spark rest api. The idea is to demonstrate a simple way to use ThingSpeak to monitor, control and log data from your core.
The line chart in the channel was updated by using the Spark.client function and by posting to the ThingSpeak API.
The actual circuit is pretty simple:
My goal was to be able to both control and monitor the core using both the Spark and ThingSpeak rest apis with a response time of a few seconds. In addition I wanted to be able to control from a dashboard.
The software is posted on Github and uses a copy of a ThingSpeak library by another author.
The ThingSpeak library was recently updated using suggestions in https://community.spark.io/t/core-becomes-unresponsive-after-http-request-solved/9285/14 to address http caching issues. I copied the ThingSpeak library and renamed it newThingSpeak to avoid a conflict in the Spark IDE. The main code is pretty simple:
// This #include statement was automatically added by the Spark IDE.
#include "newThingSpeak.h"
newThingSpeakLibrary::newThingSpeak newThingSpeak ("PutYourThingSpeakKeyHere");
// Define the pins we're going to use
int led = D0; // The led is connected here
int button = D1; // button is connected to D1
int led2 = D7; // This one is the built-in tiny one to the right of the USB jack
int analogPercent = 0; // variable to store the ThingSpeak analog value converted to percent
int analog = 0; // variable to store the analog value
unsigned long analogUpdate = 16000; // rate in ms to update ThingSpeak
unsigned long ioUpdate = 900;
unsigned long lastAnalogTime = 0;
unsigned long lastioTime = 0;
int digitalIn = 0; // variable to store the read value for the button
// This routine runs only once upon reset
void setup() {
Serial.begin(9600);
// Initialize D0 + D7 pin as output
// It's important you do this here, inside the setup() function rather than outside it or in the loop function.
delay(2000);
Serial.println('Starting up ...');
pinMode(led, OUTPUT);
pinMode(led2, OUTPUT);
Spark.function("led", ledControl); // define a function to control the led through the Spark api
Spark.variable("AI", &analog, INT); // define a function to read the analog input through the Spark api
Spark.variable("DI", &digitalIn, INT); // define a function to read the digital in through the Spark api
pinMode(button, INPUT_PULLDOWN); // define the button pin as an input
}
// This routine gets called repeatedly, like once every 5-15 milliseconds.
// Spark firmware interleaves background CPU activity associated with WiFi + Cloud activity with your code.
// Make sure none of your code delays or blocks for too long (like more than 5 seconds), or weird things can happen.
void loop() {
if(millis()-lastAnalogTime >analogUpdate) {
updateAnalog(); // update ThingSpeak every analogUpdate ms
}
if(millis()-lastioTime > ioUpdate) {
digitalIn = digitalRead(button); // read the input pin
analog = analogRead(A0); // read the analog input and return the raw 12-bit value
lastioTime = millis();
}
}
// function to read the analog value and write to ThingSpeak
void updateAnalog() {
Serial.println("Loop start");
analogPercent =100*analogRead(A0)/4095;
bool valSet = newThingSpeak.recordValue(1, String(analogPercent, DEC));
if(valSet) {
Serial.println("Value set to field 1 : " + String(analogPercent, DEC));
} else {
Serial.println("Value not set successfully");
}
bool valsSent = newThingSpeak.sendValues();
if(valsSent) {
Serial.println("Value successfully sent to thingspeak");
} else {
Serial.println("Sending to thingspeak failed");
}
lastAnalogTime = millis();
}
// function to control the led through the Spark.io api. Returns 1 if led is on, 0 if led if off, and -1 if the control message was undefined
int ledControl(String controlString) {
Serial.println("Entered ledControl loop ");
Serial.println(controlString);
if (controlString == "on")
{
digitalWrite(led, HIGH); // Turn ON the LED pins
digitalWrite(led2, HIGH);
return 1;
}
else if (controlString == "off")
{
digitalWrite(led, LOW); // Turn OFF the LED pins
digitalWrite(led2, LOW);
return 0;
}
else
{
return -1;
}
}
If one comments out the section of the code that posts to ThingSpeak:
if(millis()-lastAnalogTime >analogUpdate) {
updateAnalog(); // update ThingSpeak every analogUpdate ms
or alternatively if I post to ThingSpeak only and and do not use the Spark.variable(), things work fine. When the code is run with the http client and spark.variable functions together things go wrong and the following occurs:
- The software works as expected some of the time. The ThingSpeak channel updates, one can see the state of the core switch and one can toggle the LED on and off using the button.
- The Spark Core reboots randomly
- The ThingSpeak write fails randomly
- The Spark api calls using the Spark.variable() function fail randomly
Based on what I have read, my suspicion is that this is an http cache and/or timing issue and I am hoping that @bko and @Hootie81 or others might have suggestions on where to start troubleshooting?
