Revision 19.1
SOLO7 Transmitter User Guide
Copyright © 2013 Domo Tactical Communications (DTC) Limited. All rights reserved.
Commercial in Confidence
Page 7-44
Reply packet structure to device:
ASCII
Value
Description
STX
02h
Start byte
0123
30h-39h
4-byte unit address. In range 0001-9999
Z
20h-7Eh
1-byte status
1 (31h) = command received ok
E (45h) = error, command could not be actioned
PQR
20h-7Eh
x byte data, optional, variable length
;
3Bh
1-byte separator
X
80h-FFh
1-byte checksum
ETX
03h
End byte
The checksum is the summation of all bytes in the packet, not including the start and end bytes. An AND
operation with FFh is done to discard higher order bytes. Then an OR operation is then performed with 80h
to prevent emulation of special characters.
Below is an example showing how to build up a remote command packet for reading the board type:
1.
Packet content based on address and required command:
Address of 0001… 30h 30h 30h 31h
Command rgbty… 72h 67h 62h 74h 79h
Separators no data… 3Bh 3Bh
2.
Sum above bytes then AND/OR operation to generate checksum:
30h + 30h + 30h + 31h + 72h + 67h + 62h + 74h + 79h + 3Bh + 3Bh = 35Fh
35Fh AND FFh = 5Fh
5Fh OR 80h = DFh
3.
Combine start and end bytes with content and checksum:
02h 30h 30h 30h 31h 72h 67h 62h 74h 79h 3Bh 3Bh DFh 03h
Several situations could cause an error status to be returned:
Message is incorrectly formatted (separators in wrong place or missing).
Command mnemonic or other characters are in upper case.
Command mnemonic does not match an available command.
Checksum is incorrect.
