Jump to content
gongue2005

Modbus RS485 Master w/multiple slave

Recommended Posts

I have a problem, when a slave is disconnected (without opening the trunk network) all other slaves lose the communication of the master. Does anyone have the method or solution of how to do it?

Share this post


Link to post
Share on other sites

Perhaps the timeout and retries on the missing slave are upsetting whatever intervals you have set for the sequential reads from all the others.  Carefully go through the total possible timing per read and ensure that you have allowed sufficient "overlap clearance".

cheers,

Aus

Share this post


Link to post
Share on other sites

Thanks for your help, I posted my problem in the visilogic forum where I have 9 modbus rs485 slaves and with only one port I was able to convincingly connect up to 3 slaves. each slave has a timeout of 100 millisec to go to network failure. the data exchange is to force 5 coils and read 11 coils each. (in less than 100 millisec) so when I connect the 4th slave, it goes to failure for more than 100 millisec. (manufacturer's fixed value) softstart PSTX ABB.
with your answer I can think that each port works with 2-3 slaves. but there is another problem with unistream that in the configuration sheet, you can not decrease the speed of penny popping at less than 100 millisec.
I have added my code developed with visiligic. I'm still not happy with this work, I think I lack knowledge to have a fast 485 network (with 9 slaves)
I forget to say that slaves have only 19200 bps.

3 Vision 6 esclavos pstx.vlp

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×