M1XSP in Serial Expander Mode does not correctly transmit ^ character

[Jeffrey Bakken]

The M1XSP (Firmware 1.0.50) when operating in Serial Expander Mode (S4-S8 jumpers = 01000, RS-232) does not correctly transmit “^” character (ASCII hex 0x5E).  Alphanumeric ASCII characters and most other characters are transmitted properly, but “^” is transmitted as hex 0x01 and the following character in the output stream is skipped.  Is “^” an output character with special meaning, or is there an escape character that is intended to be used with “^”?

[Brad Weeks]

The ^ is a special (caret notation) control character for the M1. Used in a M1 ASCII text string for line feed (^J) and carriage return (^M).

[Jeffrey Bakken]

The “Help” button on the ELK RP2 “Text String” edit dialog states “Because the caret symbol (^) is used to define the special characters, to insert it literally into a string, you must enter ^@.”

I intend to send the literal string “A^A002” from the M1XSP RS232 port, so I set the text string to “A^@A002”  I expect the RS232 character sequence sent from the M1XSP to be: (hex) 41, 5E, 41, 30, 30, 32.  Instead, the actual sequence sent from the M1XSP is: (hex) 41, 01, 30, 30, 32.  It appears that the ‘@’ character is ignored and the ‘^’ operator is applied to the following ‘A’, treating it as a special (control) character.  Stated differently, the three-character text string “^@A”, is treated by the M1XSP the same as if it were the two-character string “^A” – substituting in its place a single special character – rather than achieving the expected result of sending the literal pair of characters ‘^’ and ‘A’.

Is ‘@’ the correct trailing-escape character to send a literal ‘^’?  Have I missed something in the M1XSP setup?  If this is a known issue, is there a work-around for it?

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