Re: [ts-7000] TS-7200 talking to Siemens S7-200

[russell hill <>]

Hello Sergio,

I have interfaced with many different modbus devices via RS-485, RS-232 and TCP/IP. I have not seen this before. I have seen a modbus device sending back a NAK on the function code. So for example if you send a function code 0x05 and the slave device did not like what it recieved it will raise the most significant bit and return 0x85 and the error code. Can you capture the entire data stream and post it. Perhaps using a simulator would help you caputure the paper.

sergio_dellasantina <> wrote:

I managed setting up an half duplex RS-485 (/dev/ttyAM1) data transfer
between an TS-7200 and a PLC Siemens S7-200, via modbus protocol.

The modbus messages sent by the TS-7200 are correctly received by the
S7, but the answers sent back from the S7 to the TS-7200 device have
the most significant bit of their bytes set to zero, regardless of
their real value.

For example, if the S7 sends me the byte 0xA5, I get the value 0x25,
and this happens for each byte sent.

I am sure that the S7 works correctly, maybe a wrong RS-485 setting of
the TS-7200?

Thank you very much

Sergio

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