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Re: Rs485 problems





Jarkko Tuomi wrote:
> Robert Hibberdine wrote:
> 
> 
>>cable with the Axis 82 about 70 metres from one end. Both ends of the
>>cable are terminated with 120 ohms. In this situation the application
>>can only (sometimes) see the nearer logger when using ttyS3.
> 
> 
> Try connecting the external RS485 converter to the bus to see if the
> problem is with transmission or reception
Can't do this for another week!

> Did you have the termination  resistors connected when you tested 
 > with a short cable?
Yes. Actually, it worked both with and without.


> Have you checked the grounding, i.e. that there's no large common mode 
 > voltage on the bus?
I'm just a software engineer! The hardware engineer says the grouding is 
fine. :)

> What kind of cabling and transmission rate you are using?
4 core screened cable (Belden 8273 if that means anything to you) and 
9600 baud.

Can't help thinking that if it works using the Amplcon Rs232 - Rs485
converter it ought to work using the Axis 82's ttyS3.


> Good luck,
Thanks!

> 
> Jarkko
> 
> 
> 
>