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Old January 10th, 2019, 04:47 PM   #1
Walks
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RS232 Protocol for an Ishida Weigher

Does anyone have any resources that may give specifics about the RS232 protocol from an Ishida DACS-CW? I'm going to most likely use a Comtrl DeviceMaster to read the raw ASCII data from the Ishida and have it sent over Ethernet/IP to a PLC.

I think I have a good handle on how to receive the data and use it with the PLC, but in order for me to actually create a working code, I need to know which pieces of the ASCII data to extract (e.g. product weight is IshidaDATA.[17]-IshidaDATA.[25]). From my understanding the Comtrl can transmit a ASCII string up to 128 characters. Without having the machine to test with is there any documentation that may tell me what part of the 128 char string contains the weight data?

I'm certain I'll still have to change some things when I test with the actual machine, but if I can get close enough to where I just have to change a few tag names around would be awesome.

For the record I have contacted manufactures. They have to have this information but I've always gotten either no reply or not the answer I'm looking for.

Thanks for any help!
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Old January 10th, 2019, 05:02 PM   #2
Steve Bailey
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If you can't get details from the scale manufacturer or distributor, I don't see any other way than to read a string from the scale and decode it yourself.
Having said that, I've had to do what you're attempting and in every case I've been able to get the documentation I've needed. What would be the point of offering the feature without also telling you how to handle the data? Call the local rep for the scale company and ask to speak with their tech support person.
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Old January 10th, 2019, 05:20 PM   #3
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Thanks Steve,

My guess is that they don't want to give that information out. They offer their own add-on product that does what I'm trying to do, but their add-on is very expensive for something that is quite simple and more of a "nice thing to have" rather than a "need".

While their add-on product is very good and would contain significantly more data about the machine, it's FAR more than what is needed and there is no reason to spend 5x as much.

I've kind of already accepted that I'll just have to decode the data myself but I haven't entirely given up my search yet!
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Old January 13th, 2019, 11:01 PM   #4
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If you figure your time worth anything protocol and data reverse engineering is expensive. I probably have $2,000 in hardware to snoop a serial line. It is fun I make some nice money doing it.
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Old January 14th, 2019, 11:20 AM   #5
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Jeff,

Would you be able to provide a little detail about your setup and process for decoding serial lines?

I will have a comtrl and PLC available just no machine. I planned on using software such as Termite or something similar to simulate sending serial data through the comtrl to the PLC and that way I can at least get a rough format for the code.
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Old January 14th, 2019, 11:31 AM   #6
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Frontline test equipment. Docklight buy the good version. Its worth it.

I wpuld be more concerned with the raw ASCII data. Is it really ASCII or is it modus RTU, or some other special format that only the OEM has. What Baud, parity, handshaking are they using
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Old January 14th, 2019, 01:03 PM   #7
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Well, I'm about 90% certain that it is raw ASCII data that can be used they way I want. A colleague of mine did basically the same thing with a very similar Ishida weighing machine and I believe he said that he just had to wait until he could physically connect to the machine before he could decode the data and finish the program.

I've probably been blacklisted from their support for asking for that information so many times....not really, but maybe..haha
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Old January 14th, 2019, 02:10 PM   #8
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A redlion Datastation will make short of ASCII to Ethernet IP conversion. Ive done close to a hundred of them over the years.
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Old January 14th, 2019, 02:12 PM   #9
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If you have the time you can,take the data directly into the plc and have it do the parsing.
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Old January 15th, 2019, 12:51 PM   #10
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Thank you Jeff! You have been very helpful. I finally received some of the info I needed from the manufacture, but I'll almost certainly have to decode most of it with the machine.

This is somewhat off topic, but do you or anyone else here have any experience with sending multiple RS-232 devices to the same PLC? I know RS-232 is 1 to 1, but is it at all reliable to use a multiplexer? I've looked into and I think it MIGHT work, but I'm a little nervous about adding the extra complexity.

Another option I was looking into was to somehow convert multiple RS-232 connections to a single RS-485, which from my understanding can support multiple command and listening devices. My comtrl supports RS-485.

If this is too big of a question I'll just make a separate post.
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Old January 15th, 2019, 03:42 PM   #11
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I have done several multiple 232 to 1 PLC, BUT I used a RedLion Datastarion plus. Each 232 had its own channel. You can do half duplex , it gets ugly fast.

I would have a data bridge that can handle all the comms traffic and just let it send the data to the PLC.
I can reply later im on a job now
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Old January 15th, 2019, 04:01 PM   #12
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I was actually looking at those RedLion Datastations. I think one would work, but I'm not sure I fully understand what all it can do regarding my application or how it would be different than using a Comrl DeviceMaster.

I'll only have 5 devices. If I can use a RL Datastation to connect all 5 RS232 devices and have their data sent over Ethernet/IP to a PLC with each device separately addressed that would save me a lot of time.

Even if I used a RS-485 hub to transmit all device data over a single cable, I'm not sure if a single Comtrl port will be able to differentiate between each device. 20 separate comtrl ports would be pricey.

Last edited by Walks; January 15th, 2019 at 04:14 PM.
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Old January 16th, 2019, 12:25 PM   #13
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So you only have (5) 232 devices that you need to bring,back into the PLC correct?
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Old January 16th, 2019, 01:19 PM   #14
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Technically it would be 20 devices.... There are 4 machines, each has 5 scales with their own RS232 port. I figure If I get 1 machine down I'll just do the same to other 3.

Right now the plan is to have all 5 of the RS232 connections fed through a RS232/485 converter such as the one linked. The 5 RS232 data signals would be sent through the single RS485 output on the converter.

From the converter the single RS485 cable would be fed to a RS485 > Ethernet/IP converter where it would finally be sent to the PLC so that the data from each scale can be individual recorded.

I'm not sure if the PLC supports RS485, if it does maybe I don't even need to comtrl as long as each RS232 device has it's own address than can be used by the PLC.

RS232 > 485 converter

https://www.icpdas.com/root/product/...ay/i-7527.html
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