modbus comms

ganutenator

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May 2002
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kansas
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I'm talking to 6 altivar 312 drives and 2 212 drives via modbus out of the modbus port of an M340.

I'm sending speed commands to the drives.

I would like to read additional drive data during the process, but I need to not slow down the writes.

I've partially sped this up by only sending speed changes when the sp changes.

I haven't done much w/ error checking to ensure that the drive received the change correctly.

Was thinking of creating some sort of read/write var function where I could give different data requests being passed into the function different priorities.

Anyone ever do anything like this?
 
Redlion has a feature like this - called 'favor UI writes' or something like that. I implemented your concept in a Unitronics system a while ago that did the same - it had some standard reads in a rapid cyclic sequence (ModbusTCP but it doesn't matter from a logic standpoint) but if a write (arbitrary, think higher priority) was scheduled, it became next up in the sequence to execute and bumped the reads out - did not delete it, only inserted the write into the current sequence.

Are you using a single block (i.e. one write_var block) and swapping the data in and out or separate blocks, so one write_var for each of the eight devices? I think you could implement the prioritization logic either way.
 
Redlion has a feature like this - called 'favor UI writes' or something like that. I implemented your concept in a Unitronics system a while ago that did the same - it had some standard reads in a rapid cyclic sequence (ModbusTCP but it doesn't matter from a logic standpoint) but if a write (arbitrary, think higher priority) was scheduled, it became next up in the sequence to execute and bumped the reads out - did not delete it, only inserted the write into the current sequence.

Are you using a single block (i.e. one write_var block) and swapping the data in and out or separate blocks, so one write_var for each of the eight devices? I think you could implement the prioritization logic either way.

I am willing pay you or you and others to write this for me
 

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