VS-3232DN - Protocol 3000
135
17.4 Using the Packet Protocol
The packet protocol is designed to transfer large amounts of data, such as files, IR
commands, EDID data, etc.
To use the packet protocol:
1. Send a command, for example
LDEDID
2. Receive
READY
or
ERR###
3. If
READY
:
•
Send a packet
•
Receive
OK
on the last packet
•
Receive
OK
for the command
4. Packet structure:
•
Packet ID (1, 2, 3…) (2 bytes in length)
•
Length (data 2 for CRC) - (2 bytes in length)
•
Data (data length -2 bytes)
•
CRC - 2 bytes
01
02
03
04
05…
Packet ID
Length
Data
CRC
5. Response:
~
NNNN
SP
OK
CR LF
Where NNNN is the received packet ID in ASCII hex digits.
When calculating the CRC, the polynomial for the 16-bit CRC is:
CRC-CCITT: 0x1021 = x
16
+ x
12
+ x
5
+ 1
Initial value: 0000
Final XOR Value: 0
For a code example, see:
http://sanity-free.org/133/crc_16_ccitt_in_csharp.html
CRC example:
Data = “123456789”
Result => 0x31C3
