Archive for February, 2010

Broadcast traffic is being blocked on my network, Can I still use CAS BACnet Explorer?

Published by cpascu February 23rd, 2010 in BACnet. 0 Comments

Question: Broadcast traffic is being blocked on my network, Can I still use CAS BACnet Explorer?

Answer:

Yes, but with some restrictions.

The BACnet discovery uses two services – called ‘Who-Is’ and ‘I-Am’ these messages rely on the use of broadcasts. Without the ability to send broadcast messages on a network, CAS BACnet Explorer will not be able to do the initial discovery of objects.

Once a device or objects has been added to CAS BACnet Explorer it no longer uses broadcasts messages to communicate with it. You should be able to poll a device for its object list and read/write its objects properties.

You can add BACnet objects and devices to CAS BACnet Explorer manually from the discover dialog.  You will need to know some of the devices settings. Network type, IP/MAC address, network, Device instance, Object type, Object identifier.

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SQLite vs mySQL (short summary)

Published by cpascu February 22nd, 2010 in Database and Utilities and tools. 0 Comments

If you’re trying to decide between SQLite and mySQL (which one to use as your DBMS), you must first figure out what you need. These few simple questions should point you in the right direction:

  • Do you have a storage space limit?
    • The SQLite library is a mere 250kb, which is perfect for most embeded devices that don’t come with very much storage space.
  • Do you need the database to be portable?

    • SQLite stores the database directly into a single file, which can be simply copied or moved.
    • mySQL has an export feature which lets you back the database into a single file. mySQL uses its own format for storing data so the content can’t be moved or viewed by other DMBSs. Only after the database is exported will it be portable. Depending on how large the database is, this could be time consuming.
  • Do you need security or authentication for your database?

    • SQLite does not provide an authentication system. You can add one within your application, however the database file itself can be updated/read by anyone.
    • mySQL requires a username and password to make any kind of changes to the database.
  • How large will your database get in the future?

    • SQLite requires too much memory to run if the database is over 1GB in size (256 bytes of RAM for each MB of database space).
    • mySQL can have a maximum database size of 4GB.
  • Will the database be accessed multiple times simultaneously?
    • SQLite does not handle multiple simultaneous queries well. All read operations have priority over the write operations. There is a small delay caused by this since the operations must wait their turn, which could become a problem if there are large numbers of simultaneous queries.
    • mySQL has a query mechanism which handles mutiple query operations very well.

Hopefully your basic doubts about SQLite and mySQL have now been answered.

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Same Windows (XP) license on both the host machine and virtual machine

Published by cpascu February 16th, 2010 in Operating Systems and Utilities and tools. 1 Comment

Can we use the same Windows license used with our machine’s installation to install Windows on a virtual machine (VM), which is running on top of the original installation? What is the legal method for achieving this?

Unfortunately, you cannot have a VM running Windows using the same license used on your host machine, because the VM is treated as a separate computer. The Microsoft EULA is very ambiguous when referring to virtualization:

“The term ‘COMPUTER’ as used herein shall mean the
HARDWARE, if the HARDWARE is a single
computer system, or shall mean the computer system with
which the HARDWARE operates, if the
HARDWARE is a computer system component.”

1.1 Installation and use. You may install, use, access,
display and run one copy of the SOFTWARE on the
COMPUTER. The SOFTWARE may not be used by more than
two (2) processors at any one time on the COMPUTER,
unless a higher number is indicated on the COA.”

“1.2 SOFTWARE as a Component of the COMPUTER – Transfer.
This license may not be shared, transferred to or used
concurrently on different computers. The SOFTWARE
is licensed with the COMPUTER as a single integrated
product and may only be used with the COMPUTER.”

After various forums responses from several Microsoft representatives its clear that Microsoft expects you to purchase a new license for every Windows installation.

Some legal solutions to this problem:

  • The obvious one: Buy another Windows license to use with your VM. Not very desirable, seeing as Vista and Windows 7 are each over $70. Windows XP is not even sold anymore (according to Microsoft).
  • Use Linux as the host OS, using your Windows license only on the VM (Linux has excellent VM capabilities)
  • Get Vista Ultimate along with Software Assurance from Microsoft. This allows up to 4 VM uses of the same license key.
  • See if running Linux on the VM instead of Windows suits your needs (simulate Windows using Wine, etc…), and keep the Windows installation on the host machine.
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CAS Modbus Scanner v1.02aB

Published by cpascu February 3rd, 2010 in Modbus, RS232 and RS485. 0 Comments

CAS Modbus Scanner is a utility to retrieve coils, inputs, holding registers, and input registers from a Modbus enabled device. Values retrieved from the device can be viewed in many different formats including Binary, HEX, Uint16, Int16, Uint32, Int32, and Float32.

Features:

  • Can read; coil status (0xxxx), input status(2xxxx), input registers (3xxxx), and holding registers (4xxxx)
  • Data is viewable in Binary, HEX, Uint16, Int16,Uint32, Int32, and Float32
  • Multiple connections
  • Works with RS232 and RS485, TCP
  • Easy to use interface
  • 100% Free to use, no registration required.

New

  • Works with Modbus TCP
  • Works on Windows Vista and Windows 7 (32bit and 64bit)

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