Campbell Scientific TDRSDK Software Developement Kit - Manual (Page 23)

B-1
Appendix B. TDR100 Response
Protocol
|S| quoted data |E|
S Start Character 0x3A : (colon)
E End Character 0x0D (carriage return)
“ Quote Character 0x22 “ (double quote)
Quoted Data includes
Unquoted Data
CRC-16
Quoted data is the same as unquoted data except that it doesn’t allow the bytes
(characters) colon, carriage return or double quote. When those values are
encountered in the data they are replaced with the quote character <”> followed
by the 2’s complement of the data. i.e.
unsigned char data;
data = -data;
Quoted Replacements
: 0x22C6
cr 0x22F3
“ 0x22DE
Unquoted Formats
Unquoted data adheres to the following formats with a maximum of 8200 bytes
followed by the CRC-16.. The first byte of unquoted data is “:”, and the last
byte is “cr”. The CRC is computed on the unquoted data without the first byte
, the last byte, and CRC16. CRC16 is in the Big-Endian format. Since the CRC
might have quoted characters, the CRC cannot be compared until the unquoted
data is retrieved.