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Checksum calculation in level sequences

For calculating checksum in level sequences you will need to make a dynamic calculating string.

In the example below we will use the Philips protocol!


Always start by reading the protocol of the device thoroughly.
All good configuration starts this way!
In section 2.3 of the Philips RS232 protocol we see the structure for the messages we are about to construct for the Philips display.


Notice the way the Checksum is calculated, in this case it’s done with an XOR function.

Checksum calculation in level sequences 1.png

Philips uses a protocol, where the ensure the integrity of the sent message by calculating the checksum!

The checksum is a mathematical calculation of all of the bytes prior to the checksum!

Checksum calculation in level sequences 2.png

You need Biamp Device Editor and Windows calculator in programme mode in order to calculate the checksum:

Checksum calculation in level sequences 3.png

Checksum calculation in level sequences 4.png

In this case we would like to change an input, therfore we have to do the following:

  • Find the right section in the protocol(Message Set)
  • Choose the input we want to set (HDMI 2)
  • Note the command and use the example in order to edit our command.

Checksum calculation in level sequence 5.png

Rewrite the command so that it fits:

Take the this:

Checksum calculation in level sequences 21.png

And this:

Checksum calculation in level sequences 22.png

Now what is the checksum?:

Checksum calculation in level sequences 23.png

Checksum

Now add all of the bytes like this:

Checksum calculation in level sequences 26.png

09 Xor 01 Xor 00 Xor AC Xor 06 Xor 09 Xor 01 Xor 00 = Checksum = AA

Checksum calculation in level sequences 27.png

Philips uses the Xor function, but normal addition is also very common in other protocols.

Now insert the string into Biamp Device Editor:

Checksum calculation in level sequences 7.png

This command is done, and the procedure can be repeated for all other controls:

Checksum calculation in level sequences 8.png

The next thing is to create a step volume control, where the checksum is calculated automatically.

Find the correct values in the protocol:

Checksum calculation in level sequences 9.png

Insert them in Device Editor:

Checksum calculation in level sequences 10.png

______________________________________________________________________________

Now learn your device driver to calculate the checksum automatically.

Select the bytes you wish to calculate:

Checksum calculation in level sequences 11.png

Select the target byte, where to put the checksum calculation:

Checksum calculation in level sequences 13.png

Choose the method of calculation:

Checksum calculation in level sequences 14.png

Define the field where the count is being performed.

Place your cursor in the field:

Checksum calculation in level sequences 15.png

Field is marked:

Checksum calculation in level sequences 16.png

Now press "Count" and "Define first count":

Checksum calculation in level sequences 17.png

The field now turns purple:

Checksum calculation in level sequences 18.png

 

Now Choose the in/decrease value, repeat time and step value:

Checksum calculation in level sequences 6.png

The procedure is the same for LAN!

Please also find this description attached as PDF.