Modbus TCP Communication Errors

To have good exception/error handling I recommend you to use libmodbus 2.9.3, set the debug mode (see the documentation on libmodbus.org) to display a detailed modbus request.

Could you provide your modbus source calls too?

By curiosity, which energy meters do you use (you can answer in private to avoid advertising)?

Here is example where I'm getting the communication errors:

CODE:

      modbus_param_t mbParam;
      modbus_init_tcp( &mbParam, "10.192.10.60", 502);
      uint16_t data [24];
      if ( modbus_connect(&mbParam) > -1) {
  printf("\nDevice connected\n");
  int ret = read_holding_registers( &mbParam, 1, 0x513, 1, data);
  printf("\nreturn from reading: %d\n", ret);

 }else {
   printf("\nCould not connnect to device\n");
 }

OUTPUT:
      Device connected

      ERROR Target device failed to respond (-11)

      return from reading: -11

Could you provide all requested information, please?

Hello Stéphane,

I'm going to download the 2.9.3 version and then I can give you more info.
I already sent you a email about the energy meter.

Please tell me of you need some more information.

Thank you for your reply.

Best Regards,
Nuno Santos

Yes, I need to see the request trame (libmodus is able to show it) and the modpoll command used.

Here is the request made:
[00][01][00][00][00][06][01][03][05][13][00][01]

Modpoll command:
./modpoll -m tcp 10.192.10.60 -1 -a 1 -r 513 -t 4 -c 1

Modpoll response:
modpoll - FieldTalk(tm) Modbus(R) Polling Utility
Copyright (c) 2002-2006 FOCUS Software Engineering Pty Ltd
Visit http://www.modbusdriver.com for Modbus libraries and tools.

Protocol configuration: MODBUS/TCP
Slave configuration...: Address/Id = 1, start reference = 513, count = 1
Communication.........: 10.192.10.60, port 502
Data type.............: 16-bit register, output (holding) register table

Polling slave ...
[513]: 0

Yes, I though that the value had to being passed into the function as hexadecimal. The error given leads me to look up around communication problems
Thanks for you support.

Best Regards