MODBUS Protocol

Draugar

Hi,
I have a project where I am supposed to control lights. The light controller system I have been told to talk with is an SH2WEB24, see link.
http://www.productselection.net/Pdf/UK/SH2WEB24.pdf
This unit can talk both via LAN and RS-485. Ports and bauds are all mentioned, but the protocol is nowhere to be found, even google isn't my friend on this case.
So, anyone had any experience with this system and/or MODBUS? Is it possible for me to hook their system up to a docklite, read out what is being transferred and copy this?

sling100

I haven't used that specific unit, but I have done quite a lot of modbus control from an AMX processor. The Modbus protocol is pretty standard - and there is even an open-source AMX module (of sorts) on the website. You will need to sort a few timing issues and change the ONLINE event to allow 485 control rather than the default 232, but I've done both and it works fine either way.

Simon

Draugar

Hi Simon,
Thanks for reply! Do I have to fiddle with sending binaries, or can I use regular hex? Is there a standard protocol like send_string dvRandom, "(StartOfModbus),(Set-Command),(This Address),'=',(value x%),(EndOfModbus)" ?
The project is on a boat whick I am going to tomorrow, I have 3 days to install both AV-rooms, but I suspect I won't get the light to work while I am there

sling100

Sorry - didn't see your reply. Did you get sorted?

You don't need binaries, just straight hex. If you want to change/poll more than one register at once you will need to do some bit shifting, but in reality you can do each point separately unless there are loads and loads.

Simon

Draugar

Hi Simon,
Sorry for late reply. I have not gotten sorted on this but I have left be as for now anyways. Due to little time, the electricians decided to install a button panel for the light controller right next to my touchpanel. I have asked to borrow a light controller so I can find out the protocol, but I assume the electricians have other things to bother with at the moment.