reply timeout

[Danny Dayan]

Hi stephane,

can you help me please.

im using libmodbus-3.0.6 rtu over rs485.

my master on pc

and client -embeded arm system with rs485-usb cable

the tcp working good , but in rtu i get

reply timeout or bad crc

the master is modpol

and client is with unit-test-client.c

i can recieve the request but the reply is not good.

i tried setting several byte_timout and response_timeout

thanks

danny

[Danny Dayan]

Hi,
i found that the reply is the copy of the request.
and than i get CRC error in master.
what can cause that??

danny

[Torello Querci]

Hi Danny,

which king of rs485 port are you using on PC? If you are using a 485 available on PC can you perform e test using rs485-usb converter instead?

On a lot of box that I have I need to manually manag RTS or DTO bit to be able to read data. In that cases the timing is very important.

Best regards

Torello

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[Danny Dayan]

Hi Torello,
in pc (master) -ttyUSB0
in arm-system(slave) -ttymxc0
i dont have 485 port in pc.
and the cable only have D+,D- wired. no RTS or DTO

regards,
danny

[Torello Querci]

Hi Danny

2015-03-16 11:29 GMT+01:00 Danny Dayan <da...@phase3-tech.com>:

Hi Torello,
in pc (master) -ttyUSB0
in arm-system(slave) -ttymxc0
i dont have 485 port in pc.
and the cable only have D+,D- wired. no RTS or DTO

I know but on some PC board I have RTS or DTS used to handle the bus acquisition. Of course these signals are not on the wire.

The only think that I can imagine is try to realize a 485 sniffer to be sure about what is present on the wire in addition to use debug option with libmodbus.

Best regards

Torello