Compiler Error Declaring Spark Function for Cloud

Troubleshooting
1

Howdy everyone,

I’m having some issues with publishing one of my functions to the Spark Cloud. I’m getting the following error:

invalid conversion from 'void (*)(int)' to 'int (*)(String)' [-fpermissive]

This seems to be a fairly common error (seems like I’m passing arguments around incorrectly) but unfortunately I don’t know enough C to have any idea how to fix it. I’ve looked around at a few other posts but haven’t understood the answers:

I’ve published my code below, and it’s also on Github here. To be clear: I want to pass in a color through the Spark cloud to the threshold() function — hopefully that’s actually possible.

/*
 * This is a minimal example, see extra-examples.cpp for a version
 * with more explantory documentation, example routines, how to 
 * hook up your pixels and all of the pixel types that are supported.
 *
 */

#include "application.h"
#include "neopixel/neopixel.h"

SYSTEM_MODE(AUTOMATIC);

// IMPORTANT: Set pixel COUNT, PIN and TYPE
#define PIXEL_PIN D2
#define PIXEL_COUNT 16
#define PIXEL_TYPE WS2812B

Adafruit_NeoPixel strip = Adafruit_NeoPixel(PIXEL_COUNT, PIXEL_PIN, PIXEL_TYPE);
// Code that powers the neoring. Lights up when you get tweets! Built for the Particle: https://www.particle.io/

Adafruit_NeoPixel pixels = Adafruit_NeoPixel(32, PIXEL_PIN);

uint32_t color  = 30; // rgb value

void setup() {
  pixels.begin();

  threshold(color);
  
  pixels.show();
  
  // We are also going to declare a Spark.function so that we can turn the LED on and off from the cloud.
  Spark.function("tweet", threshold);
  // This is saying that when we ask the cloud for the function "threshold", it will employ the function threshold() from this app.

}

void loop() {
  // need to have a loop function for some reason
}

// Loop animation
// Three for loops to make the animiation glow
void threshold(int color) {
  int counter = 4;
  int origColor = color;

  for (counter; counter > 0; counter--) {
    while(color > 0) {
      // dim slowly
      for(int i = 0; i < 16; i++) {
        pixels.setPixelColor(i, pixels.Color(color, color, color));
      }

      pixels.show();
      color -= 1;
      delay(50);
    }

    // dim to nothing
    for(int i = 0; i < 16; i++) {
      pixels.setPixelColor(i, pixels.Color(0, 0, 0));
    }

    pixels.show();
    delay(50);

    // get brighter again
    while (color < origColor) {
      for(int i = 0; i < 16; i++) {
        pixels.setPixelColor(i, pixels.Color(color, color, color));
      }

      pixels.show();
      color += 1;
      delay(50);
    }
    Serial.print(counter);
  }

  // Color displayed when nuthin's going on
  for(int i = 0; i < 16; i++) {
    pixels.setPixelColor(i, pixels.Color(5, 5, 5));
  }
  
  return 1;
}

Thank you so much!

2

Your function needs to look like this

//  void threshold(int color)  // this is wrong
int threshold(String sColor)
{
  int color = sColor.toInt();
  ...
  return 0;
}