Citect and CRC16 calculation

captain_is · Sep 9, 2010

Hello guyzz,

I have a problem that sounds something like this:

I need to read from Citect a energy meter (Type Algodue UPT210) over RS-485 and Modbus protocol. The connection is made and it's ok because i can see the measurements within a windows application.I need to request those measurements over Modbus and display it in a Citect project and for that i need to make a CRC calculation algorithm in CiCode.

Is anyone who encountered this kind of problem ? ..

I look forward to hear news from you.

Thanks in advance!!

tragically1969 · Sep 10, 2010

Why do you need to make a CRC check, the modbus driver in Citect should take care of everything ?

captain_is · Sep 10, 2010

no..i need to make a request for the meter to give me the informations i need.

for example :
request current measurements:

slave addr : 01
function code : 03
starting addr hi : 00
starting addr lo : 1C
number of word hi : 00
number of word lo : 10
error check : 85
C0

that value 85 C0 i need to calculate based on the rest of the message
message hex : 0103001C0010
CRC result : 85C0

and this is my problem..i don't know how to make an algorithm to do this calculation.

thanks for reply

Marsupilami · Sep 10, 2010

Thats looks like a Modbus frame and as tragically1969 said. You should use the drivers in citect to communicate with the device.

there is really no reason you would write the modbus driver in cicode. the only thing I can think of is that you want to circumvent the tag count in citect.

Marsi

tragically1969 · Sep 10, 2010

captain_is said:
no..i need to make a request for the meter to give me the informations i need.

No you dont, the driver does that, just configure an IO device to use the Modbus protocol, create your tags on the correct address and it will read them, if you need to control how often and how much data the driver reads you can set all this in the citect.ini file.

captain_is · Sep 10, 2010

this meter has registers like this in his memory
$0000 - 4 words - $1000 2 words System Voltage
$001C - 4 words - $1006 2 words System Current

I know how to configure this as an I/O device, configuring the board type COMXX, and port on this board. But how i will make the variable tags in Citect ? wich addresses will read those registers ?
like 400001 citect address reads %MW0 from a plc.

I need to say that i'm at the begining with all this stuff...and please don't be agressive

Tanks a lot for your interest!

tragically1969 · Sep 10, 2010

captain_is said:
this meter has registers like this in his memory
$0000 - 4 words - $1000 2 words System Voltage
$001C - 4 words - $1006 2 words System Current

I know how to configure this as an I/O device, configuring the board type COMXX, and port on this board. But how i will make the variable tags in Citect ? wich addresses will read those registers ?
like 400001 citect address reads %MW0 from a plc.

I need to say that i'm at the begining with all this stuff...and please don't be agressive

Tanks a lot for your interest!

I wasn't being agressive, you got an answer from me and then tried to tell me that it was wrong ?

Anyway, without the device manual in front of me i couldnt say, but at a guess if its over 2 registers it could be floating point (REAL) or a double integer (LONG) in Citect terms.

You need to check in the manual what type of registers they are.

The modbus addressing is the same, register 1000 in the device would be 401000 in modbus

Note: there may be an offset in there though depending on the driver you use so register 1000 might need to be 401001

captain_is · Sep 10, 2010

No, i was just kiddin`...it was agressive between ""...i consider all your answers and don't judge on them...because i'm very grateful for your answers...i just needed to say that i'm a begineer and maybe i say sometimes things that are really foolish..but i'm confident that this will disapear once i will get more experience..

now i want to ask you..if it is so..1000 = 401000 because it sounds logical but now i don't have time to test it...then register 101C will be?

also i need to read from that device on a PLC..and this plc (TWDLCAA16DRF) does not support floating point and double integer.

Thanks again for your understanding.

tragically1969 · Sep 10, 2010

captain_is said:
No, i was just kiddin`...it was agressive between ""...i consider all your answers and don't judge on them...because i'm very grateful for your answers...i just needed to say that i'm a begineer and maybe i say sometimes things that are really foolish..but i'm confident that this will disapear once i will get more experience..

now i want to ask you..if it is so..1000 = 401000 because it sounds logical but now i don't have time to test it...then register 101C will be?

also i need to read from that device on a PLC..and this plc (TWDLCAA16DRF) does not support floating point and double integer.

Thanks again for your understanding.

i would imagine that 101C is a hex address, you need to convert it to decimal, that would be 4134

I cant help that much with your PLC without knowing what format the analigue device stores its values in, you should be able to do some sort of conversions in the PLC

captain_is · Sep 13, 2010

i tried as you said..i created variable tags with addresses like
for $1000 in energy meter - 404097 in citect
for $101C - 404125
and my devices do not communicate...its says in kernel :
generic 000008 driver 00000257 error_in_cmd-3 16
i stucked here..

any other advices?

Citect and CRC16 calculation

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