A potential command is considered to begin when its first character is received. For the serial port this is straightforward; for the USB it is hard or impossible for the CPU to 'see' how the messages are packaged, but the overall effect is similar. In both cases the potential command has been received once the logger sees a termination character; either one of <CR> (0x0D) or <LF> (0x0A). Combinations of the two characters are dealt with as follows:
- <CR><LF>
- <LF><CR>
- <CR><CR>
- <LF><LF>
For (1) and (2), the second character is considered redundant and is discarded. For (3) and (4), the second character in either case is treated as an empty command, which simply provokes the logger's prompt, Ready: (see the prompt command).
The received message may or may not form a valid command; errors detectable by the logger will vary from one command to another, but some of the common, general errors include:
- E0102 invalid command '<unknown_text>'
- E0107 expected argument missing
- E0108 invalid argument to command: '<unknown_text>'
See Error messages for a complete list.