How to use modbus rtu to communicate esp8266 with PLC FX3u (slave)?

[vucong1612]

Hello everyone,
I have some issues when using esp8266 (nodemcu) reads data from D registers of PLC FX3u (slave) via modbus rtu (485) and create a web server. I have searched for it many days and I don't know how to do it.

Have anyone ever done this example? Can you help me?
Thank you!

Here is my code, I write similar to a source below

uint16_t au16data[16];
uint8_t u8state;
uint8_t u8query;
Modbus master(0,SerialPLC,13);
modbus_t telegram[6];
unsigned long u32wait;
uint16_t inputs[10];
uint16_t outputs[10];
uint16_t registers[20];

void initModbus()
{
    // telegram 0: read registers d10-15
    telegram[0].u8id = 1; // slave address
    telegram[0].u8fct = 3; // function code (this one is registers read)
    telegram[0].u16RegAdd = 10; // start address in slave
    telegram[0].u16CoilsNo = 5; // number of elements (coils or registers) to read
    telegram[0].au16reg = registers;

    // telegram 1: read registers d23
    telegram[1].u8id = 1;
    telegram[1].u8fct = 3;
    telegram[1].u16RegAdd = 23;
    telegram[1].u16CoilsNo = 1;
    telegram[1].au16reg = registers+5;

    // telegram 2: read registers d28-29
    telegram[2].u8id = 1;
    telegram[2].u8fct = 3;
    telegram[2].u16RegAdd = 28;
    telegram[2].u16CoilsNo = 2;
    telegram[2].au16reg = registers+6;

    // telegram 3: read registers d38-39
    telegram[3].u8id = 1;
    telegram[3].u8fct = 3;
    telegram[3].u16RegAdd = 38;
    telegram[3].u16CoilsNo = 2;
    telegram[3].au16reg = registers+8;

    // telegram 4: read registers d48
    telegram[4].u8id = 1;
    telegram[4].u8fct = 3;
    telegram[4].u16RegAdd = 48;
    telegram[4].u16CoilsNo = 1;
    telegram[4].au16reg = registers+10;

    // telegram 5: read registers d20-22
    telegram[5].u8id = 1;
    telegram[5].u8fct = 3;
    telegram[5].u16RegAdd = 20;
    telegram[5].u16CoilsNo = 3;
    telegram[5].au16reg = registers+11;

    SerialPLC.begin(19200);
    master.start();
    master.setTimeOut(5000);
    u32wait = millis() + 1000;
    u8state = u8query = 0;
}

void initWebServer()
{
    server.on("/", HTTP_GET, [](AsyncWebServerRequest *request)
    { 
        request->send(200, "text/html", index_html); 
    });

    server.on("/read", HTTP_GET, [](AsyncWebServerRequest *request)
    {
        String s = "{\"D10\":" + String(registers[0]) + ",\"D11\":" + String((registers[0]&2)>>1) + ",\"D12\":" + String((registers[0])>>2) + ",\"D13\":" + String(registers[3]) + ",\"D14\":" + String((registers[0]&16)>>4) + ",\"D28\":" + String(registers[6]) + "}" ;
        request->send_P(200, "text/plain", s.c_str()); 
    });

    server.on("/D10", HTTP_GET, [](AsyncWebServerRequest *request)
    {
        registers[0] = !registers[0];
        request->send_P(200, "text/plain", "OK"); 
    });

    server.on("/D11", HTTP_GET, [](AsyncWebServerRequest *request)
    {
        registers[1] = !registers[1];
        request->send_P(200, "text/plain", "OK"); 
    });
    server.begin();
}

source example: https://www.coder96.com/2022/06/web-server-plc-fx3u.html

[pylon]

The posted code is incomplete. Experience shows that the error is in that part of the code people are hiding from us.