espec MC-811P don't connect with PC via RS 232 rs 485 converter

[Maraudeur]

Hello all,

I'm having some difficulties setting up and RS485 link with a climate control chamber from ESPEC.
It is a MC-811P climate chamber. The climate chamber has two male DB9 connectors on the outside, apparently used for linking multiple RS485 chambers together.

The pinout of the DB9 RS485 intrerface connector is:
1: SD+ Transmission data (A) Connected
2: SD- Transmission data (B) Connected
3: RD+ Reception data (A) Connected
4: RD- Reception data (B) Connected
5: GND Ground Connected
6: GND Ground Connected
7: NC (Not connected) Not connected
8: NC (Not connected) Not connected
9: NC (Not connected) Not connected

I have bought a RS-232-to-485 interface converter . This converter also has a male DB9 interface but the pinout is different.
1: Data -
2: Data+
3: -
4: -
5: GND
6: -
7: -
8: -
9: -

So - the pinouts do not match and I see different signal names on both interfaces.

Am I correct in assuming that I should only make the following connections:

Converter 485 to ESPEC climate chamber
1 2, 4
2 1,3
3 not connected
4 not connected
5 5,6
6 not connected
7 not connected
8 not connected
9 not connected

Are there some special things I need to do to get this setup to work?
I'm using LabVIEW as my programming language to try and control the climate chamber.
I'm especially not sure how I need to set up to get everything working...
In the ESPEC documentation I could find that the communication system used is "Synchronized modulation (four-wire, half duplexing)".

[K C]

Hi,

The converter you is a (standard) Rs-485 which is normally a 2-wire interface

The climate chamber has a RS-422 4-wire interface.

It is possible to connect it the way you do but you have to be sure that the climate chamber supports this. If the climate chamber should enable the transmitter only during transmit. Not all RS-422 devices are supporting this. Check the manual of the climate chamber.

You should also look at the terminator resistors at both sides. Especially if you use a long cable. These resistors can be build in the climate chamber and converter or must be added at the connection.

Kees

[Maraudeur]

Thank you for reply, but all this I know. From manual: Communication system - "synchronized modulation(4-wire, half-duplexing)", i.e.the transmitter only during transmit as you say.  Standard Rs-485 which is normally a 2-wire interface supports the half-duplexing. So I can't understand why there is not a connection between PC and chamber. May.. you is right and my device doesn't support this..

With best regards

[K C]

Half-duplex tells you that the device cannot transmit and receive at the same time. But the TX enable is something different.

[Maraudeur]

What do you mean by "TX enable"? If you have any info about it, I would be very much obliged to you 

[K C]

You can connect the wires of the 4-wire transmitter and receiver together to create a 2-wire interface but this can only function well if the transmitter has an enable/disable like RS-485 interface circuit.

[Maraudeur]

the protocol of connenction of chamber provides

1) response from chamber only after query from PC, and

2) never by initiative of chamber

thank you for your help!

[K C]

No that is the software protocol. Simply master and slave communication.

The TX enable is hardware