PickettPLC

/*
 * PickettPLC — ESP32 Hardware Bridge Firmware
 * Compatible with PickettPLC simulator at pickettech.com
 *
 * WIRING:
 *   GPIO 18 = I0.0 (button to GND)    GPIO 22 = Q0.0 (LED/relay)
 *   GPIO 19 = I0.1 (button to GND)    GPIO 23 = Q0.1 (LED/relay)
 *   GPIO 20 = I0.2 (sensor / button)  GPIO 25 = Q0.2 (LED/relay)
 *   GPIO 21 = I0.3 (optional)         GPIO 26 = Q0.3 (LED/relay)
 *
 * HOW IT WORKS:
 *   - ESP32 creates a WebSocket server on port 81
 *   - Simulator sends output states (Q bits) as JSON every scan
 *   - ESP32 drives GPIO outputs accordingly
 *   - ESP32 reads GPIO inputs every 50ms and sends to simulator
 */

#include <WiFi.h>
#include <WebSocketsServer.h>
#include <ArduinoJson.h>

// ── WiFi credentials ──────────────────────────────────────────────
const char* WIFI_SSID     = "YOUR_WIFI_SSID";
const char* WIFI_PASSWORD = "YOUR_WIFI_PASSWORD";

// ── Input pins (INPUT_PULLUP — LOW when pressed) ──────────────────
const int INPUT_PINS[]  = { 18, 19, 20, 21 };
const char* INPUT_ADDR[] = { "I0.0", "I0.1", "I0.2", "I0.3" };
const int NUM_INPUTS = 4;

// ── Output pins ───────────────────────────────────────────────────
const int OUTPUT_PINS[]  = { 22, 23, 25, 26 };
const char* OUTPUT_ADDR[] = { "Q0.0", "Q0.1", "Q0.2", "Q0.3" };
const int NUM_OUTPUTS = 4;

// ── WebSocket server ──────────────────────────────────────────────
WebSocketsServer webSocket(81);
int connectedClient = -1;

// ── Previous input state for change detection ─────────────────────
bool prevInputState[4] = { false, false, false, false };

unsigned long lastSendTime = 0;
const unsigned long SEND_INTERVAL = 50; // ms

void setup() {
  Serial.begin(115200);
  Serial.println("\n\n=== PickettPLC ESP32 Bridge ===");

  // Setup GPIO
  for (int i = 0; i < NUM_INPUTS; i++) {
    pinMode(INPUT_PINS[i], INPUT_PULLUP);
  }
  for (int i = 0; i < NUM_OUTPUTS; i++) {
    pinMode(OUTPUT_PINS[i], OUTPUT);
    digitalWrite(OUTPUT_PINS[i], LOW);
  }

  // Connect to WiFi
  Serial.printf("Connecting to %s", WIFI_SSID);
  WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("\nWiFi connected!");
  Serial.printf("IP Address: %s\n", WiFi.localIP().toString().c_str());
  Serial.println("Enter this IP in the PickettPLC simulator");

  // Start WebSocket server
  webSocket.begin();
  webSocket.onEvent(wsEvent);
  Serial.println("WebSocket server started on port 81");
}

void loop() {
  webSocket.loop();

  unsigned long now = millis();
  if (now - lastSendTime >= SEND_INTERVAL) {
    lastSendTime = now;
    sendInputs();
  }
}

// ── Read physical inputs and send to simulator ────────────────────
void sendInputs() {
  if (connectedClient == -1) return;

  StaticJsonDocument<256> doc;
  JsonObject inputs = doc.createNestedObject("inputs");

  for (int i = 0; i < NUM_INPUTS; i++) {
    // INPUT_PULLUP: LOW = pressed = 1 in simulator
    bool state = !digitalRead(INPUT_PINS[i]);
    inputs[INPUT_ADDR[i]] = state ? 1 : 0;
  }

  String json;
  serializeJson(doc, json);
  webSocket.sendTXT(connectedClient, json);
}

// ── WebSocket event handler ───────────────────────────────────────
void wsEvent(uint8_t num, WStype_t type, uint8_t* payload, size_t length) {
  switch (type) {

    case WStype_CONNECTED:
      connectedClient = num;
      Serial.printf("Simulator connected from %s\n",
        webSocket.remoteIP(num).toString().c_str());
      // Send welcome message
      webSocket.sendTXT(num, "{\"status\":\"connected\",\"device\":\"PickettPLC-ESP32\"}");
      break;

    case WStype_DISCONNECTED:
      Serial.printf("Simulator disconnected (client %d)\n", num);
      if (connectedClient == num) {
        connectedClient = -1;
        // Safe state: turn off all outputs on disconnect
        for (int i = 0; i < NUM_OUTPUTS; i++) {
          digitalWrite(OUTPUT_PINS[i], LOW);
        }
      }
      break;

    case WStype_TEXT:
      // Receive output states from simulator and drive GPIO
      {
        StaticJsonDocument<256> doc;
        DeserializationError err = deserializeJson(doc, payload, length);
        if (err) { Serial.println("JSON parse error"); return; }

        if (doc.containsKey("outputs")) {
          JsonObject outputs = doc["outputs"];
          for (int i = 0; i < NUM_OUTPUTS; i++) {
            if (outputs.containsKey(OUTPUT_ADDR[i])) {
              int val = outputs[OUTPUT_ADDR[i]];
              digitalWrite(OUTPUT_PINS[i], val ? HIGH : LOW);
            }
          }
        }
      }
      break;

    default:
      break;
  }
}