ESP32 Overview

#include <Arduino.h>

// PWM output: this is connected to the LED in this first safe experiment.
// Later, the same output can feed a suitable MOSFET driver for a DC pump.
constexpr int PWM_OUTPUT_PIN = 25;
constexpr int PWM_FREQUENCY_HZ = 5000;
constexpr int PWM_RESOLUTION_BITS = 8;
constexpr int PWM_MAX = (1 << PWM_RESOLUTION_BITS) - 1;

int pumpPercent = 0;
int directionStep = 1;
unsigned long lastUpdateMs = 0;

void setPumpPercent(int percent) {
  pumpPercent = constrain(percent, 0, 100);
  int duty = map(pumpPercent, 0, 100, 0, PWM_MAX);
  ledcWrite(PWM_OUTPUT_PIN, duty);

  Serial.print("PWM command: ");
  Serial.print(pumpPercent);
  Serial.print("%  |  duty: ");
  Serial.println(duty);
}

void setup() {
  Serial.begin(115200);
  ledcAttach(PWM_OUTPUT_PIN, PWM_FREQUENCY_HZ, PWM_RESOLUTION_BITS);

  Serial.println("ESP32 PWM demo started.");
  Serial.println("The LED represents pump speed: dim = slow, bright = fast.");
  Serial.println("Type a number from 0 to 100 in Serial Monitor, then press Send.");
  setPumpPercent(0);
}

void loop() {
  // A typed value, such as 65, replaces the automatic demonstration level.
  if (Serial.available() > 0) {
    int requestedPercent = Serial.parseInt();
    if (requestedPercent >= 0 && requestedPercent <= 100) {
      setPumpPercent(requestedPercent);
    } else {
      Serial.println("Please enter a whole number from 0 to 100.");
    }
    while (Serial.available() > 0) {
      Serial.read();
    }
  }

  // Move the simulated pump speed up and down once every 50 ms.
  if (millis() - lastUpdateMs >= 50) {
    lastUpdateMs = millis();
    pumpPercent += directionStep;

    if (pumpPercent >= 100) {
      pumpPercent = 100;
      directionStep = -1;
    } else if (pumpPercent <= 0) {
      pumpPercent = 0;
      directionStep = 1;
    }

    int duty = map(pumpPercent, 0, 100, 0, PWM_MAX);
    ledcWrite(PWM_OUTPUT_PIN, duty);
  }
}