Modbus RTU reception problems.

[asmatec]

While carrying out a project, I realized that during the data transmission through the Modbus RTU protocol, the signal was sent without problems but the reception of the signal did not occur, pin 7, that controls the MAX3485 Modbus controller chip, does not activate the reception of the input signal to the microcontroller. Do you know why this happens? Is it a library problem? Thanks.

[BenR]

Hello,

Please can you attach your project .fcfx file so we can investigate.

[asmatec]

Yes, I do. The communication stage is repair. I use a different adapter from Serial to RS485, which doesn't use the direction pin. Now I have a different problem, when I send the data bytes, the Modbus macro give a byte with the result of the communication, and always return CRC error, (1). I attach the project, an image of the connection and finally the documents I use. In the image appears a PCB, its the module I try to communicate with. Thanks.

[BenR]

Hello,

In the Modbus component properties the UART Receive Timeout is set to 0, this should probably be something more like 100 to allow it time for the slave to process the command and issue the reply. Hopefully this will solve the problem for you.