190-01115-01 G3X™/G3X Touch™ Avionics Installation Manual
Rev. AV Page C-1
APPENDIX C RS-232 TEXT OUTPUT FORMAT
This data is output from a GDU™ 37X/4XX display RX-232 port that has been configured to the “Text
Out” format.
C.1 Electrical Interface
The output signals are compatible with RS-232C. Data is generated at 115,200 baud with a word length of
8 bits, one stop bit, and no parity.
C.2 Message Output Selection
Text messages are grouped into categories. Categories may be enabled or disabled in configuration mode.
Enabling or disabling one category has no effect on the other categories. Enabling a category will result in
all messages of that category being sent out the RS-232 port. This may be one or more messages depending
on which category is enabled.
C.3 General Message Output Format
Most text output messages have the following general format:
• Escape character ('=' symbol, 0x3D hex)
• ID character
• Version character
• Data characters (length determined by message ID)
• Checksum - 2-character (1-byte) ASCII hex value that is the simple sum of all previous
bytes, including the escape character
• Carriage return (0x0D hex)
• Line feed (0x0A hex)
An exception to the above is the GPS Data message, which is backwards compatible with the Garmin
Simple Text Output format described at:http://www8.garmin.com/support/text_out.html
. The GPS Data
Message has the following general format:
• Escape character ('@' symbol, 0x40 hex)
• Data characters
• Carriage return (0x0D hex)
• Line feed (0x0A hex)
All text output messages use only printable ASCII characters. For all messages, a value that is out of range,
missing, not configured, uncalibrated, or otherwise invalid is indicated by replacing the corresponding
bytes within the message with the underscore character ('_', 0x5F hex).
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