I have troubles in the communication between a ECMB (Energy meter communication board, brand Schneider) that permits communicate through Modbus RTU, and the gateway EGX100 (of Powerlogic, brand Schneider) that permits communicate between Modbus and Ethernet. Then i am trying to test it with Modscan installed in my laptop, but i can't achieve the right answer. I don't know if the problem is the way to use the MODSCAN then i wish some help to locate the problem and do a reliable test.

The data are: i have communication right between the Energy meter and the communications card, the LEDs indicate the communication between EMCB and main frame is OK. The communication between the laptop and EGX is OK because i checked it with IPCONFIG and the LEDs of EGX are OK in that part. The problem are the LEDs (of EGX) of RS485 communication that are OFF indicating there isn't communication. I installed the MODSCAN to send some registers and check what happen, but not happen nothing, mark not received and TIMEOUT. Also i changed the RS485 cable twice and i've been checked changing the connection.

The help i need mainly is advice to do a reliable test using this testing software (MODSCAN) and maybe some advise if someone have experience with this devices to share with me. Maybe the equipment is not OK and i can probe it.

Thank you very much

My best regards
Jorge Guespi

 

I too have had trouble getting MODSCAN to communicate. I had much better results with Simply Modbus, a small stand-alone test program that shows everything in one window. Hopefully it will work better for you too.

 

> I too have had trouble getting MODSCAN to communicate. I had much better
> results with Simply Modbus, a small stand-alone test program that shows
> everything in one window. Hopefully it will work better for you too.

Thank you very much Tim...i will try...Any version that you recommend?

Best regards
Jorge Guespi

 

I use both Modscan32 and Simply Modbus. Either is entirely functional and suitable for establishing and proving serial or ethernet link communication to Modbus slaves.

The first task in using either software package is to configure and establish the comm link, serial or ethernet, with associated setup parameters (port; baud/word/parity/stop; IP).
Somewhere there's a selection for the serial protocol: RTU or ASCII.

Subsequent tasks involve selecting an RTU slave node address, a word format and register addressing.

My approach is 'divide and conquer', starting with the slave:

1) get the PC Modbus master talking to the ECMB serial RS-485 port so that it can do a read.

This probably requires a USB/RS-485 serial converter or an RS-232/485 converter to connect directly to the serial device. Each serial converter needs a driver installed on the PC.

Use the Master program to read a value from the slave device. Pick a register with a value that you know is not zero (empty registers frequently default to zero). Getting a wrong value can be a one offset address issue, wrong register number, wrong instruction reading the wrong part of the map, wrong word format.

Once you accomplish a read, then do a write, if needed. Check the slave's documentation to confirm that the slave register will accept a write.

Connecting the PC directly to the serial device confirms its operation and lets you check how the LEDs blink for read or a write operation.

Since there's no convention for serial A/B designations, it pays to know what a good, working LED pattern looks when you connect the gateway converter's serial side directly to the device, in case the gateway serial line connections need to be swapped.

2) Configure the gateway converter. Some converters need a firmware upgrade out-of-the-box, some need the Modbus 'handler app' installed.

The converter has two 'sides'; an ethernet side and a serial side. Each 'side' needs configuration that is appropriate for the device or network that it will be on. Gotta read the manual for details.

3) Connect the converter's serial port to the device's serial port and use the PC's Modbus master program to read/write the same registers via the ethernet port, proving the network-to-serial functionality via the gateway.

4) Once the PC's Modbus master can talk to the slave device through the gateway, connect the SCADA/HMI to the network, configure the Modbus driver's port for ethernet and work through a tag read operation.

 

Hello,

You can use the modbus scanner from www.modbus.pl to check if your configuration for the connection is correct.

Regards
Andrzej