Both posts are bad links. I'll use the VW85 protocol.

38400, 8-Even-1

All commands are 8 bytes long.

Byte 0 - Start Code - Always "A9"
Byte 1 - Item Number Upper Byte - From Item List - Table 1
Byte 2 - Item Number Lower Byte - From Item List - Table 1
Byte 3 - Type - Always "00" for setting a value or "01" for querying
Byte 4 - Data Upper Byte - From Item List - Table 2, left 2 digits
Byte 5 - Data Lower Byte - From Item List - Table 2, right 2 digits
Byte 6 - Checksum - Byte 1 to Byte 5 using the "Or" function
Byte 7 - End Code - Always "9A"

Let's try setting the Wide Mode to Zoom.
Item Number Upper Byte= 00
Item Number Lower Byte= 20
Data Upper Byte= 00
Data Lower Byte= 03

So:
Byte 0=A9 -Start Code
Byte 1=00 -Wide Mode Upper Byte
Byte 2=20 -Wide Mode Lower Byte
Byte 3=00 -Set
Byte 4=00 -Zoom Upper Byte
Byte 5=03 -Zoom Lower Byte
Byte 6=23 -Checksum (See below)
Byte 7=9A -End Code


The Checksum is calculated by using the "Or" function. The best way to do this is by using Windows Calculator. You must put the calculator into scientific or programmer mode to show the "Or" function. You must also change from DEC to HEX. The checksum is the result of the Or function from Byte 1 through Byte 5. The "Or" function works just like + or -.

00 or 20 or 00 or 00 or 03 = 23