Search results

Since you're just trying to test your software, don't focus too much on the hardware connection (serial cable). There is no such concept as configuring software to be straight-through vs. crossover, this is a hardware-only concept and just dictates how the cable is wired. In software (i.e...

The load limitation of RS-485 is defined as 32 "Unit Loads". For older RS-485 devices, it may be true that 1 device presents 1 unit load on the bus. However, nowadays, there are many devices out there that present a fraction of a unit load, such as 1/4, 1/8, or even 1/10, onto the RS-485 bus...

Is the variable table a table of tags that you created or is it the raw I/O data array? If it is tags, is it possible for you to monitor the raw input data array? From reading the PLX51-PBM's manual, it doesn't seem that gateway has any diagnostics features that would allow you to confirm that...

Let's try to determine if the problem lies between your PROFIBUS master and the PLX51-PBM or if the problem is between the PLX51-PBM and your Modbus server device. You stated, "Receiving data but only for the first 8 registers from modbus to the input words. All the received data is correct and...

Modbus registers are 2 bytes each. Using a 16-byte input module could explain why you're only seeing 8 registers. You may need to use a 32 byte input module to see 16 Modbus registers. Have you mapped 16 Modbus Holding Registers per slot or 16 in total (presumably 8 per slot)?

I don't have any experience with the PLX51-PBM, just going off of the user's manual available here: https://www.prosoft-technology.com/prosoft/download/13492/295876/file/PLX51_PBM_UM.pdf How do you have your PROFIBUS master's I/O configured (i.e. what module(s) from the PLX51-PBM's GSD file are...

Which object are you attempting to write to? From what I believe is the relevant documentation (https://www.lochinvar.com/lit/574437100305786_2000558371_Rev%20C_AWH%20Modbus%20Bacnet%20Manual%20(Add%20AWH_KBX).pdf), it seems there are two Analog Values for the setpoint: AV2 "0-10 Volt Input /...

What does your bus monitor show with the DB05 disconnected? If it still shows RX bytes, that means your USB to RS-485 adapter is receiving its own transmissions. Some adapters have an "Echo" setting to enable and disable this functionality.

How are you wiring the DB05 to your USB to RS-485 adapter? The DB05, as you said, is a 4-wire RS-485 device. However, the adapter you show is a 2-wire RS-485 device. It's unclear whether your adapter has 2 independent channels (i.e. (1)TX/RX+ vs. (2)TX/RX+) or if the pins labeled (1) vs (2) are...

What kind of 10Kohm variable resister are you using? Is it linear or logarithmic? Your description sounds like you may be using a logarithmic potentiometer, but are expecting the behavior of a linear potentiometer. https://forum.digikey.com/t/linear-vs-logarithmic-potentiometer-test/3809

I've seen a lot of Modbus implementations over the last 15+ years helping customers integrate our gateway products to other equipment, but I've never come across anything like Case 1. It seems whoever built this custom PLC didn't actually implement Modbus, but rather simply implemented "test"...

Are you asking how to write an entire SECS/GEM simulator using C#? Have you written any code yet? And I have to ask, is this a homework assignment? If not, what is the purpose of this program, as opposed to just using the Ignition SECS/GEM Simulator?

Are you using the Ignition SECS/GEM Simulator or are you creating your own program that has the same functionality?

I can't comment on the secs/gem protocol specifically, but when developing communication drivers for TCP/IP protocols, you can start both a server and client on your local computer and target the loopback address (127.0.0.1) from your client to test communications. If you want to test...

OK, I think I see the problem and source of the confusion. In Modbus "0X addresses" means Coils (for completeness, Input Statuses are 1X, Holding Registers are 4X and Input Registers are 3X). I have a complete write up on this here...

The good news is that an exception response means you are communicating with the device from ModScan (wiring, baud rate, parity, and device address are correct). The next step is to find out what exception code the Modbus module is returning. The only way I know how to do this in ModScan is to...

I think there may be some confusion on the EtherNet/IP protocol here. It is perfectly fine for multiple EtherNet/IP devices to use the same local tag for data (otherwise you could never have two of the same product on one EtherNet/IP network). But, of course, you would need to store the data...

You should consider using a computer and a USB to RS-485 adapter to test communications to each piece of equipment separately. You can use software such as ModScan (as the Modbus master) to test communications to the inverter, and ModSim (as the Modbus slave) to test communications to the...

Your DOS-based data acquisition system very likely uses hardware handshaking and the new computer you're using (and the software running on it) to replace the serial printer is not doing the handshaking. Here's a helpful post describing RS-232 handshaking...

Your inverter is a 2-wire RS-485 device, not a 4-wire. The signals are just duplicated, likely for daisy-chaining purposes. Therefore you should connect the devices as follows: MB3130 Inverter Pin 3 (D+) Pin 1 485_B Pin 4 (D-) Pin 2 485_A Pin 5 (GND) Pin 3 GND-485 Note that there...