Weintek cMT2078x Modbus Addressing Help

Ignition
1

I've got a new machine in the plant that I'm trying to get Modbus TCP setup on. The OEM sent me some information on the setup, for example

READ 100 RECORDS STARTING FROM 400
ReadValues = modbusClient.ReadInputRegisters(400, 100)

MACHINE STATUS
REGISTER 400 -> 1=RUN  2=STOP

Based on a Weintek PDF I found online input registers are 3x, so my Ignition OPC tag path is ns=1;s=[Silo A]3x400 which gives me a bad quality. What am I missing?

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2

If that's the literal address you're using you missed the part where you read the Ignition user manual to understand the Modbus address syntax. 3x400 is not a valid address.

It would maybe be something like [Silo A]IR400.

https://docs.inductiveautomation.com/display/DOC81/Modbus+Addressing#ModbusAddressing-ModbusSpecificAddressing

3

Weintek has gone out on a limb defining non-existent address types. There's no such thing as a 5x address, though the functionality described can be configured on an Ignition driver. The protocol spec has a totally different definition for 6x addresses, with dedicated function codes.

4

I read the manual first. I took it that 3x was the prefix, and using the device address mapping tool generated the ns=1;s=[Silo A]3x400, which I see is wrong now. 3x just means the 30000 range.

I tried the manual address of [Silo A]IR400 but it didn't work.

5

I figured it out :slight_smile: I was able to hack the admin password into the Weintek HMI. With easybuilder pro, I downloaded the project from the HMI, and decompiled it. They had the Modbus unit id set to 1 where I was trying to use unit id 0.

2 Likes
6

@Kevin.Herron Seems I need a little help on string conversion.

IR480-499 are being read as 16int. I set up a tag with path [Silo A]1.HRS480:20

  • Without any string handling options I get an empty string.
  • With reverse byte order, I get Z
  • With read raw string checked, I get Z Pillow 4
  • Change path to [Silo A]1.HRS480:40, I get Z Pillow 43OZCAC`

The manual says that each word is 2 characters, but best I can tell I only have one char per word.

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7

What string are you expecting? You may have some trouble here, the Modbus driver doesn't so Strings in any kind of sane manner.

8

Sorry, I meant to include that in the last post
Z Pillow 43 OZ is the correct value

9

[Silo A]1.HRS480:40 is probably closest to what you want.

This means read 40 bytes, aka 20 registers. The string either has to be fixed width or null terminated.

edit: if you're expecting null-terminated, make sure the raw strings option is false.

1 Like
10

I think it is null terminated, 0 in ascii should be null; therefore the null would be RecipeName15

hmm, I reloaded the recipe name on the HMI, and it started acting completely different. I had to reverse the byte order and then uncheck the raw string option and it worked as expected :man_shrugging:

11

Eww. That suggests that different parts of its code do strings differently.

12

Weird, with HRS480:40 the string must be over 20 chars long for it to read correctly. If I do 20 chars or less, it only shows the very first character in the string. So weird.