// =================================================================================================

// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to ModbusClient

// MIT license - see license.md for details

// =================================================================================================

// Includes: <Arduino.h> for Serial etc., WiFi.h for WiFi support

#include <Arduino.h>

#include <WiFi.h>

// Modbus server TCP

#include "ModbusServerTCPasync.h"

#ifndef MY_SSID

#define MY_SSID "WiFi network ID"

#endif

#ifndef MY_PASS

#define MY_PASS "WiFi network password"

#endif

char ssid[] = MY_SSID; // SSID and ...

char pass[] = MY_PASS; // password for the WiFi network used

// Create server

ModbusServerTCPasync MBserver;

uint16_t memo[32]; // Test server memory: 32 words

// Server function to handle FC 0x03 and 0x04

ModbusMessage FC03(ModbusMessage request) {

ModbusMessage response; // The Modbus message we are going to give back

uint16_t addr = 0; // Start address

uint16_t words = 0; // # of words requested

request.get(2, addr); // read address from request

request.get(4, words); // read # of words from request

// Address overflow?

if ((addr + words) > 20) {

// Yes - send respective error response

response.setError(request.getServerID(), request.getFunctionCode(), ILLEGAL_DATA_ADDRESS);

}

// Set up response

response.add(request.getServerID(), request.getFunctionCode(), (uint8_t)(words * 2));

// Request for FC 0x03?

if (request.getFunctionCode() == READ_HOLD_REGISTER) {

// Yes. Complete response

for (uint8_t i = 0; i < words; ++i) {

// send increasing data values

response.add((uint16_t)(addr + i));

}

} else {

// No, this is for FC 0x04. Response is random

for (uint8_t i = 0; i < words; ++i) {

// send increasing data values

response.add((uint16_t)random(1, 65535));

}

}

// Send response back

return response;

}

// Setup() - initialization happens here

void setup() {

// Init Serial monitor

Serial.begin(115200);

while (!Serial) {}

Serial.println("__ OK __");

// Connect to WiFi

WiFi.begin(ssid, pass);

delay(200);

while (WiFi.status() != WL_CONNECTED) {

Serial.print(". ");

delay(500);

}

IPAddress wIP = WiFi.localIP();

Serial.printf("WIFi IP address: %u.%u.%u.%u\n", wIP[0], wIP[1], wIP[2], wIP[3]);

// Set up test memory

for (uint16_t i = 0; i < 32; ++i) {

memo[i] = (i * 2) << 8 | ((i * 2) + 1);

}

// Define and start RTU server

MBserver.registerWorker(1, READ_HOLD_REGISTER, &FC03); // FC=03 for serverID=1

MBserver.registerWorker(1, READ_INPUT_REGISTER, &FC03); // FC=04 for serverID=1

MBserver.registerWorker(2, READ_HOLD_REGISTER, &FC03); // FC=03 for serverID=2

MBserver.start(502, 1, 20000);

}

// loop() - nothing done here today!

void loop() {

static unsigned long lastMillis = 0;

if (millis() - lastMillis > 10000) {

lastMillis = millis();

Serial.printf("free heap: %d\n", ESP.getFreeHeap());

}

}