Hi everyone, I'm having a problem. I want to establish communication between my ESP32 (as a Modbus TCP client) and a Modbus Slave software in my PC via the RJ45 port. I'm using the LAN8720 module for the Ethernet connection.
However, I haven't been able to make it work, and I'm not sure if there's something wrong with my code.
First, this is my schematic, and I didn't use the resistors shown in the picture:
Second, this is my Modbus Slave interface:
And finally, here is my source code:
#include <ETH.h>
#include <ModbusIP_ESP8266.h>
// I²C-address of Ethernet PHY (0 or 1 for LAN8720, 31 for TLK110)
#define ETH_PHY_ADDR 1 // DEFAULT VALUE IS 0 YOU CAN OMIT IT
// Type of the Ethernet PHY (LAN8720 or TLK110)
#define ETH_PHY_TYPE ETH_PHY_LAN8720 // DEFAULT VALUE YOU CAN OMIT IT
// Pin# of the enable signal for the external crystal oscillator (-1 to disable for internal APLL source)
#define ETH_PHY_POWER -1 // DEFAULT VALUE YOU CAN OMIT IT
// Pin# of the I²C clock signal for the Ethernet PHY
#define ETH_PHY_MDC 23 // DEFAULT VALUE YOU CAN OMIT IT
// Pin# of the I²C IO signal for the Ethernet PHY
#define ETH_PHY_MDIO 18 // DEFAULT VALUE YOU CAN OMIT IT
// External clock from crystal oscillator
#define ETH_CLK_MODE ETH_CLOCK_GPIO0_IN // DEFAULT VALUE YOU CAN OMIT IT
// Cấu hình địa chỉ IP tĩnh cho ESP32
IPAddress localIP(192, 168, 1, 100); // Địa chỉ IP của ESP32
IPAddress subnet(255, 255, 255, 0); // Subnet mask
IPAddress gateway(0, 0, 0, 0); // Không có gateway
IPAddress dns1(0, 0, 0, 0); // Không có DNS
IPAddress modbusServerIP(192, 168, 1, 30); // Address of Modbus Server device
const int startRegister = 0; // Starting holding register
const int numberRegister = 10; // Number of holding registers to read
const int interval = 1000; // interval between reads (in milliseconds)
ModbusIP modbus;
uint16_t res[numberRegister];
void setup()
{
Serial.begin(115200);
// Khởi tạo kết nối Ethernet
ETH.begin(ETH_PHY_ADDR, ETH_PHY_POWER, ETH_PHY_MDC, ETH_PHY_MDIO, ETH_PHY_TYPE, ETH_CLK_MODE);
// Cấu hình Ethernet với IP tĩnh và subnet
if (ETH.config(localIP, gateway, subnet, dns1))
Serial.println("Ethernet initialized successfully.");
else
Serial.println("Failed to initialize Ethernet.");
// Kiểm tra kết nối Ethernet
if (ETH.linkUp())
Serial.println("Ethernet connection established.");
else
Serial.println("Ethernet connection failed.");
modbus.client();
modbus.connect(modbusServerIP, 502);
if (modbus.isConnected(modbusServerIP))
Serial.println("Connect to Server successfully!");
else
Serial.println("Connected to Server failed!");
}
void loop()
{
if (modbus.isConnected(modbusServerIP))
{
// Read holding registers from Modbus Slave
uint8_t transaction = modbus.readHreg(modbusServerIP, startRegister, res, 10, nullptr, 1);
// Wait for the transaction to complete
while (modbus.isTransaction(transaction))
{
modbus.task();
delay(10);
}
// Print holding register values
Serial.println("Holding Register Values:");
for (int i = 0; i < numberRegister; i++)
{
Serial.print("Register ");
Serial.print(i);
Serial.print(": ");
Serial.println(res[i]);
}
}
else
{
// If not connected, try to connect
Serial.println("Unconnected!");
modbus.connect(modbusServerIP);
}
delay(interval);
}
It always prints "Unconnected", even though I can ping the ESP32's IP address from my CMD and it responds.