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MODBUS - Incorrect response

APC UPS for Home and Office Forum

Schneider Electric support forum for our APC offers including Home Office UPS, Surge Protectors, UTS, software and services and associated products designed to share knowledge, installation, and configuration.

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ltrost_apc
Crewman
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MODBUS - Incorrect response

This was originally posted on APC forums on 4/19/2011


I have a Symmetra-LX Single Phase unit with Building Management Integration Card (AP9622). At this time, there is no load on the UPS. I poll the unit using MODBUS (via the holding register function) and RS-232 serial connection. I am able to successfully retrieve information for all but three registers based on the "Single-Phase Symmetra Modbus Register Map" dated 10/2007 and the "Building Management Integration Card Addendum-Register Descriptions" documentation. The three registers are as follows:

0x4001F: Bypass Input Voltage - Phase B
0x40037: Measure-UPS Contact Position
0x40048: Battery Current

When a request of these three registers is performed, I receive a invalid and, what appears to be, a corrupted MODBUS response.

Another problem involves the values received for 5 registers:

0x40015: Utility Input Current Phase A : value returned is 121 amps (decimal), expected value is 0-5 amps
0x40017: Bypass Input Voltage Phase A: value returned is 207 volts (decimal), expected value is 120 V
0x4001C: Peak Output Current Phase A: value returned is 121 amps (decimal), expected value is 0-5 amps
0x4001E: Utility Input Current Phase B: value returned is 207 amps (decimal), expected value is 0-5 amps
0x40025: Peak Output Current Phase B: value returned is 209 amps (decimal), expected value is 0-5 amps

Enclosed is the request and responses for all polled registers which do not involve the three registers which gave suspect responses in hex format.

The proper values are seen on the front panel LCD of the UPS for these 5 registers. All other registers are correct.

Thanks in advance for any insight you can provide.

Larry

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BillP
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Re: MODBUS - Incorrect response

This reply was originally posted by Angela on APC forums on 5/9/2011


i did get in at 9600 which i believe is the default baud rate. i am just not a modbus expert so it takes me a while..its like reading a foreign language. i was trying to use the program modbus poll which takes a little getting used to.

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ltrost_apc
Crewman
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Re: MODBUS - Incorrect response

This was originally posted on APC forums on 5/12/2011


I downloaded the program "modbus poll" and installed it. I was able to get it to work. Enclosed are 3 screen shots of the configuration settings for communications and the poll request format. These are for polls with absolute starting registers 0 to 6 (decimal) and a one for absolute starting register 21 (Utility Input Current Phase A). Note that the window "Communication Traffic". It shows the transmits and receive data in HEX format for each poll. I also polled for the "Bypass Input Voltage - Phase B" and received the same response in hex. The application alos displayed the error message " SLAVE DEVICE FAILURE".

I had a type-oh in the first message. It should be 0x40016 for the "Bypass Input Voltage Phase A" instead of 0x40017.

Hope this helps you understand MODBUS and the application you are using a bit better.

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BillP
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Re: MODBUS - Incorrect response

This reply was originally posted by Angela on APC forums on 5/13/2011


hi larry,

i really appreciate you taking the time to put that together. i will be back in the office next week to mimic those settings and re-try.

BillP
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Re: MODBUS - Incorrect response

This reply was originally posted by Angela on APC forums on 5/16/2011


alrighty, I think we got some where. someone a lot more experienced with modbus gave this a try and came to a conclusion that there are a few issues.

4001F (31) - This one appears to be indeed reporting incorrectly and will be logged.
40037 - (55) - As I mentioned mentioned, with no Measure-UPS installed, this register is not used.
40048 - (72) - This one isn't supported. Symmetra LX does not support battery current in the particular value that the Modbus card looks for on this register.
40015 - (21) - 121 - Not working due to issue with 4001F
40016 - (22) - 207 - Not working due to issue with 4001F
4001C - (28) - 121 - This one is reporting an output voltage and will be logged.
4001E - (30) - 207 - Register not supported by LX, the card is getting some value and reporting it back which is incorrect.
40025 - (37) - 209 - Register not supported by LX, the card is getting some value and reporting it back which is incorrect.

ltrost_apc
Crewman
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Re: MODBUS - Incorrect response

This was originally posted on APC forums on 5/17/2011


OK. Thanks for the support. No problem on providing additional information

Any idea on how long it will take to resolve the logged issues and what we then have to do to receive and implement the fix? This may be beyond the scope of this forum, but just wanted to ask. Also, will this mean updates to the register map and addendum?

Should I close out this thread?

ltrost_apc
Crewman
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Re: MODBUS - Incorrect response

This was originally posted on APC forums on 5/18/2011


I have no further issues from a technical perspective.

Just a question on understanding things from a customer perspective. How is one notified when the new version of the card is available? Do you need some Point of Contact information?

BillP
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Re: MODBUS - Incorrect response

This reply was originally posted by Angela on APC forums on 5/17/2011


i know someone was working on adjusting the maps yesterday but i am not sure on the actual fix for the card itself. generally, those cards aren't upgradable in the field and would require a hardware replacement, which is not an issue because we could send you one. the bugs would need to be reviewed by the product manager as far as priority, etc so i just don't have an answer at this point to be honest.

you can close out the thread if you'd like. let me know if you need anything else.

BillP
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Re: MODBUS - Incorrect response

This reply was originally posted by Angela on APC forums on 5/18/2011


hi larry,

i will send you an email. because this particular card has a firmware chip, it is not usually something we notify people about unfortunately. for network management card firmware updates that get released regularly, i believe there is a mailing list.

BillP
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Re: MODBUS - Incorrect response

This reply was originally posted by Angela on APC forums on 4/19/2011


hi Larry,

What Rev of the AP9622 are you using? this can be found on the card itself on a sticker, something like Rev H or through the console interface on AP9622 using 940-0103 cable at 9600 baud rate.

Measure-UPS Contact position should only give you a response if you are using an AP9612TH Measure UPS card, which is an older, legacy type accessory. I assume you are not using this and may have an AP9619 or AP9631 NMC along with the AP9622 in your Symmetra LX. please confirm where the AP9622 and other devices are installed - top or bottom slot.

i'd have to look and see if battery current is even supported from this particular UPS. i assume it is since it is on the register map.

lets find out the rev of your card. from there, i may have to plan on testing some of this as well, but to be honest, i might not be able to until next week but i'd like to help.

ltrost_apc
Crewman
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Re: MODBUS - Incorrect response

This was originally posted on APC forums on 4/27/2011


Hello,

Thanks for the response.

The AP9622, located in the bottom slot, is using Rev. H.

AP9619 is not being used in this configuration so the top slot is empty.

Hope this helps.

Larry

BillP
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Re: MODBUS - Incorrect response

This reply was originally posted by Angela on APC forums on 4/28/2011


ok, i will try to look into this next week when i have access to an LX with an AP9622.

BillP
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Re: MODBUS - Incorrect response

This reply was originally posted by Angela on APC forums on 5/5/2011


sorry, just getting to this today...i should have results later today to post.

EDIT_ - not being a modbus expert, i am trying to use modbus poll without much luck. what settings to you use and are you using a 0 based system or 1 based system. i guess i am having trouble being able to poll values which i got to work once but i am not sure what settings i should be using.

not sure if you could tell me what you're doing so i can try to get it to work?

BillP
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Re: MODBUS - Incorrect response

This reply was originally posted by Angela on APC forums on 5/9/2011


i did get in at 9600 which i believe is the default baud rate. i am just not a modbus expert so it takes me a while..its like reading a foreign language. i was trying to use the program modbus poll which takes a little getting used to.