Understanding Registers Help

[bburford]

Fernando, all of that was written by a programmer - Yuk.
Most of it describes how Modbus works and isn't relevant to just using it.

What you need is probably in Tables 6-15, 6-30, 6-31 and 6-32
Print them and use the programming option of Windows Calculator to convert them back to Decimal Register values ie 0FFDH is Hex value 0FFD = 4093 Decimal.

Word means it is 16 bit (one "register" only), DWord means it is 32 bit (two consecutive "registers" - but in some instances they are in reverse order).
It doesn't say they are Signed Values (1st bit is a +/- sign) so assume not.

16 bit Registers are a gimme because there is no possibility of Big Endian / Little Endian reverse order problems - they are either there or not. Try and find these first.

R/W means you can read and Write from the register in this case Read means Type 3 "Read Holding Registers" and Write is Type 16 "Write Multiple Holding Registers".

The Modbus PlugIn sorts the Type 3 / Type 16 out itself depending on whether you ask it to Read or Write but does need to be told to to write Multiple Registers (Register Write Function) because single Register Writes (Type 6) are not valid for your meter.

Create a Modbus IP Gateway pointed at the Slave (Meter) IP address and TCP Port 502 (unless it has been changed). Set a 10 Sec poll interval for now and remember the Write Multiple Register option. Leave Big Endian and Zero Addressing blank. Note if you have multiple Modbus IP Slaves they will need a gateway setup for each.

I would start by trying to read the Baud Rate at 1002H (4098) as it is a 16 bit register and you know what you've set it to.

Create a device (Register) within the Gateway.
In Status Graphics Tab you need to Add New Range Value and give it Value Limits (-65438 => 65438 should be safe although Float Values can be very large). If the value received is outside these limits the Modbus Plugin will stop with an Error. At first just try to Read the Register - set Status-Control to Status.

In the Modbus Tab, select the Gateway you just set up, Register Type Holding Register, Slave ID 1 (usually default for IP Modbus because the IP Address itself is unique - sometimes it is still 1 even if an alternative address is able to be programmed!). Add the Register Address (4098), Return (Data) Type of Int16, leave Signed Value blank, Multiplier 1, and select Read Only and Device Enabled.

If it doesn't work, try one register lower and then one register higher. If one of these works you can toggle Zero Based Addressing in the Gateway to offset the Registers by one and try to make them line up with the documentation.If you cant it doesn't matter - just adjust your Register List to suit. If you need to adjust this register then every other Register in the device WILL have the same Offset (unless the documentation is extremely poor).

Note if you cant find 16 bit data at any of the three consecutive addresses it is most likely you have a comms problem of some sort as it should be easy.

After you've found a Register and tested on a few other 16 Bit Registers move to Table 30 etc. These have an Address of two "Registers" so are either 32 Bit Float or Int32 (dword) as specified. Usually the lowest address of the two is the "Register Address" that you enter.

Here's where it gets tricky. The two 16 Bit words are normally read and the bits lined up in order 32->17 16->1 but not always. Depending upon the vagaries of the device programmer they may be lined up in Reverse Order 16->1 32->17. The Big Endian toggle will fix this.

Again look for something you know and keep trying until you find a a valid entry. Line Voltage is always a safe bet in an Energy Meter.

Coils are easier - the same Register Offset will apply but data possibilities are only 0 and 1. Again the Plugin will switch to Type 1 Read or Type 5 Write Single Coils or Type 15 Write Multiple Coils as required.

Sometimes binary data is stored in a standard Holding Register - it may even be available in both so you can choose. Sometimes you get a choice of data type ie Float in one Register Range and Int in another with both containing the same data.
Modbus' biggest strength is that it is extremely configurable.
Modbus' biggest weakness is that it is extremely configurable.
You need to work out what the programmer was trying to achieve.

[FernandoSolanes]

Thanks guys for your response.

I have the device connected to my ethernet network and can read the values on the web page but they update slowly and figured Modbus would be the best way to update the virtual homeseer devices..


Here is the link to the device manual, and also a paste of the section that includes how the device comunicates its values.

https://www.accuenergy.com/files/acu...-1040E1303.pdf



5.2.10 Description of Modbus-TCP protocol
The Modbus-TCP protocol is used for communication in Ethernet modules. The
protocol sets up master/slave link in Ethernet. First, master device (client) sets
up TCP link with slave device (server). Second, master device sends request
frame to slave device, and slave device receives request frame and returns
response frame to master device. Fig 5-41 displays working mode of ModbusTCP
protocol.
159
Modbus Client Modbus Server
Request Indication
Confirmation Response
Fig 5-41
1. Protocol
a. Data Frame Format
Table 5-2
MBAP Header Function Data
7x8-Bits 8-Bits Nx8-Bits
b. Modbus Application Header (MBAP Header) Field
The Modbus application header field is the start of the data frame and consists
of seven bytes.
Table 5-3
Field Length Description
Transaction
Identifier 2 Bytes Identification of a Modbus Request/Response transaction
Protocol Identifier 2 Bytes Modbus protocol=0
Length 2 Bytes Number of following bytes
Unit Identifier 1 Byte Slave address, in the range of 0~247 decimal.
c. Function Field
The function code field of a message frame contains eight bits. Valid codes are
in the range of 1~255 decimal. When a message is sent from a client to a server
device the function code field tells the server what kind of action to perform.
160
Table 5-4
Code Meaning Action
01 Read Relay Output Status Obtain current status of Relay Output
02 Read Digital Input(DI) Status Obtain current status of Digital Input
03 Read Data Obtain current binary value in one or more registers
05 Control Single Relay Output Force Relay to a state of on or off
16 Write Multiple-registers Place specific value into a series of consecutive
multiple-registers
d. Data Field
The data field is constructed using sets of two hexadecimal digits, in the range
of 00 to FF hexadecimal. The data field of messages sent from a master to slave
devices contains additional information which the slave must use to take the
action defined by the function code. This can include items like discrete and
register addresses, the quantity of items to be handled, and the count of actual
data bytes in the field. For example, if the master requests a slave to read a
group of holding registers (function code 03), and the data field specifies the
starting register and how many registers are to be read. If the master writes to
a group of registers in the slave (function code 10 hexadecimal), the data field
specifies the starting register, how many registers to write, the count of data
bytes to follow in the data field, and the data to be written into the registers.
2. Format of communication
Explanation of frame
Table 5-5
Transaction
identifier hi
Transaction
identifier lo
Protocol
identifier hi
Protocol
identifier lo Length hi Length lo Unit
identifier
00H 00H 00H 00H 00H 06H 01H
Fun Data start reg hi Data start reg lo Data #of regs hi Data #of regs lo
03H 40H 00H 00H 48H
161
As shown in Table 5-5 the meaning of each abbreviated word is:
Transaction identifier hi: Transaction Identifier high byte
Transaction identifier lo: Transaction Identifier low byte
Protocol identifier hi: Protocol Identifier high byte
Protocol identifier lo: Protocol Identifier low byte
Length hi: length high byte
Length lo: length low byte
Unit identifier: slave address
Fun: function code
Data start reg hi: start register address high byte
Data start reg lo: start register address low byte
Data #of regs hi: number of register high byte
Data #of regs lo: number of register low byte
a. Read Status Relay (Function Code 01)
Function Code 01
This function code is used to read relay status in Acuvim II series meter.
1=On 0=Off
There are 8 Relays in the meter, and the starting address is 0000H.
The following query is to read 2 Relays Status of the meter Address 1.
162
Query
Table 5-6 Read 2 Relays Status Query Message
Transaction
identifier hi
Transaction
identifier lo
Protocol
identifier hi
Protocol
identifier lo Length hi Length lo Unit
identifier
00H 00H 00H 00H 00H 06H 01H
Fun Data start reg hi Data start reg lo Data #of regs hi Data #of regs lo
01H 00H 00H 00H 02H
Response
The Acuvim II series meter response includes MBAP Header, function code,
quantity of data byte and the data. For example response to read the status of
Relay 1 and Relay 2 is shown as Table 5-6. The status of Relay 1 and Relay 2 is
responding to the last 2 bit of the data.
Table 5-7 Read 2 Relays Status Response Message
Relay 1: bit0 Relay 2: bit1
Transaction
identifier hi
Transaction
identifier lo
Protocol
identifier hi
Protocol
identifier lo Length hi Length lo Unit
identifier
00H 00H 00H 00H 00H 04H 01H
Fun Byte count Data
01H 01H 02H
The content of the data is,
7 6 5 4 3 2 1 0
0 0 0 0 0 0 1 0
MSB LSB
(Relay 1 = OFF , Relay 2=ON)
163
b. Read Status of DI (Function Code 02)
Function Code 02
1=On 0=Off
There are 38 DIs in the meter, and the starting address is 0000H.
The following query is to read the 4 DIs Status of address 1 of Acuvim II series
meter.
Query
Table 5-8 Read 4 DIs Query Message
Transaction
identifier hi
Transaction
identifier lo
Protocol
identifier hi
Protocol
identifier lo Length hi Length lo Unit
identifier
00H 00H 00H 00H 00H 06H 01H
Fun Data start
reg hi
Data start
reg lo
Data #of regs
hi
Data #of regs
lo
02H 00H 00H 00H 04H
Response
The response includes MBAP Header, function code, quantity of data characters
and the data characters.
An example response to read the status of 4 DIs (DI1=On, DI2=On, DI3=On, DI4=
On) is shown as Table 5-9. The status of each is responding to the last 4 bit of the
data.
164
Table 5-9 Read 4 DIs Response Message
DI1: bit0 DI2: bit1 DI3: bit2 DI4: bit3
Transaction
identifier hi
Transaction
identifier lo
Protocol
identifier hi
Protocol
identifier lo Length hi Length lo Unit
identifier
00H 00H 00H 00H 00H 04H 01H
Fun Byte count Data
02H 01H 0FH
The content of the data is,
7 6 5 4 3 2 1 0
0 0 0 0 1 1 1 1
MSB LSB
c. Read Data (Function Code 03)
Query
This function allows the users to obtain the measurement results of Acuvim II
series meter.
Table 5-9 is an example of reading the 6 measured data (Time) from server
device address 1, the data start address is 1040H.
Table 5-10 Read Time Query Message
Transaction
identifier hi
Transaction
identifier lo
Protocol
identifier hi
Protocol
identifier lo Length hi Length lo Unit
identifier
00H 00H 00H 00H 00H 06H 01H
Fun Data start
reg hi
Data start
reg lo
Data #of
regs hi
Data #of
regs lo
03H 10H 40H 00H 06H
165
Response
An example response to read Time (2006-12-18 14:15:20) is shown as Table 5-10.
Table 5-11 Read Time Response Message
Transaction
identifier hi
Transaction
identifier lo
Protocol
identifier hi
Protocol
identifier lo Length hi Length lo Unit
identifier
00H 00H 00H 00H 00H 0FH 01H
Fun Byte
count
Data1
hi
Data1
lo
Data2
hi
Data2
lo
Data3
hi
Data3
lo
Data4
hi
Data4
lo
Data5
hi
Data5
lo
Data6
hi
Data6
lo
03H 0CH 07H D6H 00H 0CH 00H 12H 00H 0EH 00H 0FH 00H 14H

[beerygaz]

1. Does your meter support Modbus?
2. What protocol?
3. Do you have an IP to RS485/RS232 modbus gateway or a direct serial connection to the meter?
4. Do you have any documentation for the meter that might help us work out how to get you connected?

[Qbus]

There is a lot more than Modbus in book, but this is what I give to new techs in the building automation industry.

https://www.ccontrols.com/ncbpost.htm

[FernandoSolanes]

I managed to get the plugin in trial installed and i believe the gateway (IP) tests fine

Im trying to poll my Acuvim II utility meter but i have absolutely no clue how the register and values work.
I tried random settings etc but can get any value responses
Is anyone familiar with the AcuvimII meter?