Appendix D. RS-232 and RS-485 Operation
D-12
D.6.2 Information Message Output
The measurement output string for the SR50AT is as follows:
<STX>aa;SSSSS;H.H;F.F;BBBBB;WWWWW<CR><LF><ETX>
<STX> is the hex character 0x02 (2 in decimal)
aa
These two characters are the serial address of the sensor. The default is 33.
Note this is two ASCII characters of 0x33 in hexidecimal or 51 in decimal.
SSSSS
This is the serial number of the sensor.
H.H
This is the hardware version of the sensor.
F.F
This is the firmware version of the sensor.
BBBBB
This is the checksum of the boot code.
WWWWW
This is the checksum of the firmware.
CC
This is a two-character checksum of the data packet. The checksum is the two’s
complement of the data packet sum including control characters.
The least significant byte is used resulting in a two-character checksum.
<STX> = &h02 (hexadecimal)
<CR> = &h0D (hexadecimal)
<LF> = &h0A (hexadecimal)
<ETX> = &h03 (hexadecimal)
The following is a sample packet with proper checksum:
<STX>33;1838;194;11011;2C<CR><LF><ETX>
SUM =
02+33+33+3B+31+38+33+38+3B+31+39+34+3B+31+31+30+31+31
+3B+0D+0A+03
=0x3D4
Use Last byte only (D4) and calculate two’s complement = 100 – D4 = 2C
<CR>
Carriage return character. &h0D in hexadecimal or 13 in decimal
<LF>
Line feed character. &h0A in hexadecimal or 10 in decimal
<ETX>
End of transmission character. &h03 in hexadecimal or 3 in decimal
