RS-485 Distinguishing v3 from v4 Meters

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simonprickett
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Joined: Mon May 15, 2017 12:53 pm

RS-485 Distinguishing v3 from v4 Meters

Post by simonprickett » Mon May 15, 2017 1:07 pm

Hi there - sorry if this is covered elsewhere, I tried searching... I'm writing some software that will receive RS-485 data from some EKM meters which could be v3 or v4 meters. I'm wondering if there's any easy way in the RS-485 hex data to know from checking a couple bytes if it's a v3 or v4 that generated the message?

I looked at the PDF docs for communication parsing and I'm thinking the "Model" bytes would be suitable, from the docs "10 17" would be a v3 and "10 24" would be a v4? Or is that too simplistic and are there other places / values I should look for?

Thanks,

Simon.

Jameson
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Re: RS-485 Distinguishing v3 from v4 Meters

Post by Jameson » Tue May 16, 2017 10:34 am

Hello Simon,

Welcome to the forum! When you make a meter request (you will make either a v3 type request or a v4 type request), you call for a given meter number and you get a meter response that includes both the "Model" information and the meter number.

1. Yes, you can use the 2 bytes for "Model" to distinguish between v3 and v4 meters.

2. You can also use the meter number format. v3 meter numbers look like either 000000024567 or 10001234 and v4 meter numbers look like 000300001234 or 000350001234

3. You can also use your awareness of making a v3 meter request to a given meter number (you would expect a v3 response from the same meter number)

Let me know if you would like more information.
Jameson
EKM METERING
http://www.ekmmetering.com
831.425.7371

simonprickett
Posts: 5
Joined: Mon May 15, 2017 12:53 pm

Re: RS-485 Distinguishing v3 from v4 Meters

Post by simonprickett » Tue May 16, 2017 10:59 am

Hi Jameson - thanks for the welcome and the quick reply!

I'm working on a server side component that won't be making the original request, so I'll be receiving the meter's response as an MQTT message from a Raspberry Pi which will in turn talk to the meter via RS485. The Pi making the requests to the meter will have some awareness of meter serial numbers and versions, so it will know which request type to send to the meter itself.

As we want to absolutely minimize the amount of data going between the Pi and the server component I am writing, we didn't want to add more to the MQTT message to tell the server what sort of meter the data is coming from, so I think I'll use item (1) from your list above, will check out (2) as well.

Thanks, I'll keep you posted if we have other questions.

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