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I need to write a software program to communicate with a DX9100 controller.

Does anybody know how to calculate the data checksum/BCC (Block Check Code) for DX9100?

Thanks in advance.

Hello. IŽm Victor from Argentina. I can help you with that function. It is composed by the previous ASCII characters Sum (you have to take the low part of the sum). I would like to be in touch with you to interchange information and may be you need some additional help in the future.

Thank you.
Regards,
Victor

Hello Victor,

Thanks for your reply. Beside the 2 checksum characters you mention. I think there are additional 4 characters checksum. May I know that checksum is in what format? CRC16 or any other format? How can I contact you, how can I know your email? I still not very familiar using this forum...

Thank you.

Regards,
wclai

Hello, please find my e-mail address in my web site that is www.factory-solutions.com.ar.

Thank you.

Regards,
Victor.

Here write the code used to make the checkSum to comunicate with UNT and VAV of the JCI protocol N2, I'm not sure if this, work good with DX9100.

For i = 1 To Len(Command)
suma = suma + Asc(Mid(Command, i, 1))
Next
ByteHi = Int(suma / 256)
Resto = suma - ByteHi * 256 ' recupera el resto de la división

CheckSum = Format2Hex(Resto)
End Function

The S4 Group is in the business of providing integrations between proprietary building automation systems and open protocols.

We had the same problem only on a much larger scale. We recently released our S4 Open: OPC-N2 Router product which communicates to any Johnson Controls Metasys N2 controller via OPC.

In order to create our products we had to start with the documentation provided by JCI on their N2 Open protocol and then reverse engineered all of the N2 protocol variations. Communications to System-91 devices, like the DX-9100, is just one of the variations. You will find that there is a long way to go to have successful and reliable communications in addition to solving the BCC algorithm. There are a number of timing issues that have to be addressed, the N2 bus can only have one bus master, etc.

Using our product could get you to your goal of communicating with the DX-9100 much quicker than trying to reverse engineer the interface yourself. If you want details about how our system works you can download a white paper at http://www.thes4group.com. Please feel free to contact me directly if you want to discuss more details about your integration project requirements.