GSM module connected via RS485

[Tomas]

Hello,

I would like to ask you for help with connecting the GSM module Cinterion BGS2T via RS485 (modbus).

Does anyone have experience example of how to connect GSM SMS sending via RS485 not RS232.
Thank you

Tomas

[kratmel]

Hi,

I do not use Cinterion BGS2T via RS485, but i try to read some manuals and find - it is not modbus device. RS485 is only  variant of communication interface.

Then you can find p.14

https://www.activexperts.com/files/manuals/cinterion-bgs2t-at-command-set.pdf

and use modem via external RS232 to RS485 convertor (it is not possible to select RS485 in Visilogic modem settings).

 

But i think - better way is to change this modem to Unitronics UCR product.

[Tomas]

Thank you for your answer. I am not sure if I catch your idea. My problem is I have v430 with 1 port 485 (already used). I need send SMS." it is not possible to select RS485 in Visilogic modem settings" - I supose I can not use RS485 for GSM in Visilogic and libraries. 

[kratmel]

You did not specify which PLC was used. Therefore, I recommend adding an additional port V100-17-RS4/V100-17-RS4X to V430.

This will allow you to connect a standard modem via RS232. 

33 minutes ago, Tomas said:

I supose I can not use RS485 for GSM in Visilogic and libraries. 

This is probably true.

However, nothing prevents you from transmitting commands to the modem via additional port RS232 port (and external convertor RS232 to RS485 if no RS232 port present on modem).

Please,  describe your configuration - what your existing RS485 port is used for, what modem you have, or maybe you haven't chosen it yet.

[Tomas]

My configuration,

v430-J-T38, I have already installed additional port ethernet (for remote connection). 1 Port RS485 I use for communication by Modbud with electricity meters.

It's my problem that I don't have another port to use as RS232.

I guess it has no solution?

Thank you

[AlexUT]

Hi Tomas,

All Unitronics PLCs are designed to work with supported modems "peer-to-peer" by use of RS232 interface.

RS485 interfacce cannot be used.

B.R.

 

[Tomas]

Thank you for your answer.

B.R.

[kratmel]

53 minutes ago, Tomas said:

I guess it has no solution?

One old trick that can be used for solve problem with one communication port.

If you read installation manual

https://www.unitronicsplc.com/wp-content/uploads/2015/12/Vxxx_J_T38_INSTAL-GUIDE_01-15.pdf

you can find Port 1 pinout table and some information below:

Note that it is possible to establish a PC to PLC connection using RS232 even when the PLC is set to
RS485 (this eliminates the need to open the controller to set jumpers).
To do so, remove the RS485 connector (pins 1 & 6) from the PLC and connect a standard RS232
programming cable.
Note that this is possible only if DTR and DSR signals of RS232 are not used (which is the standard
case).

If you can temporarily not read the readings from your meter, then with the help of an external relay connected to the logic output, you can switch the connection between the modem and the meters while changing the configuration of the communication port in the program.

Switching between different types of modems is shown in the example from Unitronics.

I think you understand the idea. Therefore, from time to time you will be able to send SMS if necessary, but during the transfer - no meter readings will be received.

[AlexUT]

Kratmel,

I c annbot recommend this for field use.

1. PLC attempting to read meter, and contineously will return COM port settings to RS485.

2. When connecting PC and activate VisiLogic communication - PC send BREAK signal to RS232 and change protocol to PCOM (7, E, 1), which is not compatible for modem (8.N, 1).

3. Possible colution (but not perfect) is to make COM INIT for RS485 and for RS232 in separate Nets.

Use modem communication , then make COM INIOT for RS485 and read from meter.

8Use 1 and 6 pins to connect meter.

Use 2,3,4,5 pins to connect modem.

This will not always work at field.

B.R.

 

*Both modes cannot be used.

[kratmel]

2 hours ago, Tomas said:

additional port ethernet (for remote connection)

present on this PLC (maybe Visilogic and remote connection)  then only Meter RS485 / Modem RS232 changeover needed.

To prevent problem with strange data comes to modem or meter i recommend relay switch.

Maybe it is not perfect solution but i think it possible.

[Tomas]

Thank you for your time.

1 hour ago, kratmel said:

you can find Port 1 pinout table and some information below:

Note that it is possible to establish a PC to PLC connection using RS232 even when the PLC is set to
RS485 (this eliminates the need to open the controller to set jumpers).
To do so, remove the RS485 connector (pins 1 & 6) from the PLC and connect a standard RS232
programming cable.
Note that this is possible only if DTR and DSR signals of RS232 are not used (which is the standard
case).

I had the same idea. And I tried it but not function (because there is HW switch  on board).

B.R.

[kratmel]

You can connect meter to RS485 and after that - change cable, do not change dip and try to connect to modem via standard 4 wire connection. 

I think if you manage RS485 to RS232 change in program - modem connection is possible without dip change.