communicating with eurotherm 2704 via RS485

[Sholyoake]

Hi There,

I'm trying to develop an application to control and communicate with 5 Eurotherm 2704 controllers on the same bus, the program works with RS232 but I cannot get it to connect via RS485, I have all the correct modules installed in the Eurotherm unit and I have tried every concievable wiring configuration, loopback tests via MAX show that the port is working

eventually I hope to be able to connect to a cRIO-9068 unit, however I'm unable to establish comms, I'm thinking it may be a voltage level issue, has anyone else successfully connected a 2704 controller to a cRIO unit of any type via RS485?

is there any specific issue that anyone is aware of?

many thanks

[chiara.a]

Hi, 

The KnowledgeBase article whcih describes how to connect these up is here: http://digital.ni.com/public.nsf/allkb/D31BAE31637E9D2D8625669F00671AAD?OpenDocument

Have you connected up the pins as described therein, and have you connected the device up in "2 wire TX Rdy Auto" mode?  

Best wishes, 

[Sholyoake]

I am informed by Eurotherm tech support that the 2704 unit will only operate in 5-wire connectivity, the article you linked says to connect in 3-wire topology by bridging pins, I am informed this will not function...

can you please inform me how to connect in "2 wire TX Rdy Auto" mode?

I appreciate your response

Simon

[chiara.a]

Hi,

I'm very sorry, but that is the only information I can find on the NI side about the correct topology to connect up the Eurotherm board, and I believe it's our recommended setup with our serial boards - it may be worth checking with their tech support for further suggestions if you find that this doesn't work.

In terms of changing the port settings - instructions can be found here: http://digital.ni.com/public.nsf/allkb/1D516C10D7EDFAC6862571110073B8F4

I hope this helps!