Maximum number of MODBUS commands/feedbacks

Hello Matthijs,
our command has checked work of Modbus controller and to be exact import from CSV, 4000 commands and 4000 feedback channels. Everything worked correctly, the project asked for data and sent commands. Recommended frequency of request is 10000 ms. Actually every register must work with about 56535 addresses but it depends on controller power.


With regards,
Victoria Vaynert.

Thank you Victoria,

That's clear, next thing:
I need "real time" feedback, so when a button is pushed in iridium i need the feedback object directly.

I noticed that this doesnt work so well when i have so many adresses programmed, its running on 500ms now and thats too much time in my opinion, when i make the update time lower it seems the controller or iridium can't keep up.

Is there a workaround for this? and what's the absolute minimum time for 4000 adresses?

I cannot answer your questions. It depends on a controller you use. Please test it on your own and then you can send us your feedback!


With regards,
Victoria Vaynert.

I'm using a Wago 750-881 controller, when tested it to communicate with an other 881 controller via ethernet, i can send/receive 4000 word variables in 50ms, Iridium cannot handle this so thats where my question came from.

Dear Matthijs, you can request about 200 variables (the usual number is 40-60). You mix two things: every 50 ms 1 transaction is requested to a little group of addresses not to 4000. If 4000 addresses are requested it will take more time. At best a controller can request in 1000-2000 ms using iRidium. And moreover speed depends on connection to the controller: connection can be direct among controllers, or they can be connected via router.
With regards,
Victoria Vaynert.

Okay,

will adapt to that then, is there a possibility to just receive variables when they are changed?
this makes the data-traffic a lot less.

It is impossible, iRidium requests for data and if it doesn't request you will not receive any variables. For more information how iRidium for Modbus driver works read here: http://wiki2.iridiummobile.net/Modbus


Have a good day,
Victoria Vaynert.

Thank you very much for the quick and clear replies Victoria!

Matthijs, you are always welcome!