#include <SoftwareSerial.h>
#include "FastLED.h"

#define NUM_LEDS 4
#define DATA_PIN 6
#define CLOCK_PIN 7
#define RX 2
#define TX 3

SoftwareSerial serial (RX, TX);

CRGB leds[NUM_LEDS];
unsigned char i = 0;
unsigned int counter = 0;
unsigned char val; //data from serial port

CHSV spectrumcolor;

void setup() { 
  serial.begin(115200);
  delay(50);
  serial.println("Hello, world?");
  FastLED.addLeds<APA102, DATA_PIN, CLOCK_PIN>(leds, NUM_LEDS); 
  spectrumcolor.hue =     222;
  spectrumcolor.saturation =  255;
  spectrumcolor.value =     100;
}

void loop() {
  if (serial.available()){
    val = serial.read();
  }

  spectrumcolor.hue = val;
  
  i=0;
  for(i; i<NUM_LEDS; i++){
    //leds[i] = CHSV(counter, 255, 100); //use counter instead of val for continuous rainbow
    hsv2rgb_spectrum( spectrumcolor, leds[i] );
  }
  FastLED.show();
  //counter++; use counter to smoothly cycle through rainbow
}