Sorry for the confusion, I tried to convert the original code myself while trying to teach myself. Here is the original code
#include <ESP8266WiFi.h>
#include <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels
#define OLED_RESET -1 // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);
String apiKey = "xxxxxxxxxxxxxxxxxxxxxxxxx; // Enter your Write API key from ThingSpeak
const char *ssid = "xxxxxxxx"; // replace with your wifi ssid and wpa2 key
const char *pass = "xxxxxx";
const char* server = "api.thingspeak.com";
#define LED_BUILTIN 16
#define SENSOR 2
long currentMillis = 0;
long previousMillis = 0;
int interval = 1000;
boolean ledState = LOW;
float calibrationFactor = 4.5;
volatile byte pulseCount;
byte pulse1Sec = 0;
float flowRate;
unsigned long flowMilliLitres;
unsigned int totalMilliLitres;
float flowLitres;
float totalLitres;
void IRAM_ATTR pulseCounter()
{
pulseCount++;
}
WiFiClient client;
void setup()
{
Serial.begin(115200);
display.begin(SSD1306_SWITCHCAPVCC, 0x3C); //initialize with the I2C addr 0x3C (128x64)
display.clearDisplay();
delay(10);
pinMode(LED_BUILTIN, OUTPUT);
pinMode(SENSOR, INPUT_PULLUP);
pulseCount = 0;
flowRate = 0.0;
flowMilliLitres = 0;
totalMilliLitres = 0;
previousMillis = 0;
attachInterrupt(digitalPinToInterrupt(SENSOR), pulseCounter, FALLING);
}
void loop()
{
currentMillis = millis();
if (currentMillis - previousMillis > interval)
{
pulse1Sec = pulseCount;
pulseCount = 0;
// Because this loop may not complete in exactly 1 second intervals we calculate
// the number of milliseconds that have passed since the last execution and use
// that to scale the output. We also apply the calibrationFactor to scale the output
// based on the number of pulses per second per units of measure (litres/minute in
// this case) coming from the sensor.
flowRate = ((1000.0 / (millis() - previousMillis)) * pulse1Sec) / calibrationFactor;
previousMillis = millis();
// Divide the flow rate in litres/minute by 60 to determine how many litres have
// passed through the sensor in this 1 second interval, then multiply by 1000 to
// convert to millilitres.
flowMilliLitres = (flowRate / 60) * 1000;
flowLitres = (flowRate / 60);
// Add the millilitres passed in this second to the cumulative total
totalMilliLitres += flowMilliLitres;
totalLitres += flowLitres;
// Print the flow rate for this second in litres / minute
Serial.print("Flow rate: ");
Serial.print(float(flowRate)); // Print the integer part of the variable
Serial.print("L/min");
Serial.print("\t"); // Print tab space
display.clearDisplay();
display.setCursor(10,0); //oled display
display.setTextSize(1);
display.setTextColor(WHITE);
display.print("Water Flow Meter");
display.setCursor(0,20); //oled display
display.setTextSize(2);
display.setTextColor(WHITE);
display.print("R:");
display.print(float(flowRate));
display.setCursor(100,28); //oled display
display.setTextSize(1);
display.print("L/M");
// Print the cumulative total of litres flowed since starting
Serial.print("Output Liquid Quantity: ");
Serial.print(totalMilliLitres);
Serial.print("mL / ");
Serial.print(totalLitres);
Serial.println("L");
display.setCursor(0,45); //oled display
display.setTextSize(2);
display.setTextColor(WHITE);
display.print("V:");
display.print(totalLitres);
display.setCursor(100,53); //oled display
display.setTextSize(1);
display.print("L");
display.display();
}
if (client.connect(server, 80)) // "184.106.153.149" or api.thingspeak.com
{
String postStr = apiKey;
postStr += "&field1=";
postStr += String(float(flowRate));
postStr += "&field2=";
postStr += String(totalLitres);
postStr += "\r\n\r\n";
client.print("POST /update HTTP/1.1\n");
client.print("Host: api.thingspeak.com\n");
client.print("Connection: close\n");
client.print("X-THINGSPEAKAPIKEY: " + apiKey + "\n");
client.print("Content-Type: application/x-www-form-urlencoded\n");
client.print("Content-Length: ");
client.print(postStr.length());
client.print("\n\n");
client.print(postStr);
}
client.stop();
}