DISCUSSION

Introduction
This technical document outlines the information output by the 312 and 315 built-in NMEA combiner under input error conditions. In order to observe these error codes, you must run HyperTerminal and monitor the NMEA combiner output port (com4). The NMEA combiner uses the special NMEA 183 sentence “PNOLE” to output combiner status.


Format
The PNOLE sentence identifies the channel(s) in error and error type(s) with an alphanumeric code. The format is as follows:
$PNOLE, ,

The error message is sent only once each half second when errors are present. The message will contain a summary of all channels with errors and error types which occurred during the previous half-second interval.


Channel Codes
The channel(s) in error (GPS, Depth, Autopilot Input) and the error code(s) are each represented by a single character. This means that when multiple channels have error conditions a single character is used to indicate this. The meanings of these characters are as follows:
Channel Code 1: Autopilot Input
Channel Code 4: GPS
Channel Code 5: Autopilot Input + GPS
Channel Code 8: Depth
Channel Code 9: Autopilot Input + Depth
Channel Code C: GPS + Depth
Channel Code D: Autopilot Input + GPS + Depth


Error Types
The combiner outputs error codes for the following error types:
Error Type: sync
Cause: Synchronization or Framing Error
Notes: Invalid START or STOP bits. Usually caused by corrupted data.

Error Type: char
Cause: Character Error
Notes: Most significant bit of character (d7) is a ‘ONE’

Error Type: dolr
Cause: Start of Sentence Expected
Notes: The NMEA start of sentence indicator ($) was not received when expected.

Error Type: lnfd
Cause: Missing linefeed/overflow
Notes: Sentence contains too many characters before linefeed

Error Type: ovfl
Cause: Buffer Overflow
Notes: More data input than can be output.


Error Codes
As with the Channel Code, a single character Error Code can represent multiple simultaneous errors. The single character codes for these errors are:
Error Code 1: sync
Error Code 2: char
Error Code 3: sync + char
Error Code 4: dolr
Error Code 5: dolr + sync
Error Code 6: dolr + char
Error Code 7: dolr + char + sync
Error Code 8: lnfd
Error Code 9: lnfd + sync
Error Code A: lnfd + char
Error Code B: lnfd + char + sync
Error Code C: lnfd + dolr
Error Code D: lnfd + dolr + sync
Error Code E: lnfd + dolr + char
Error Code F: lnfd + dolr + char + sync
Error Code G: ovfl
Error Code H: ovfl + sync
Error Code I: ovfl + char
Error Code J: ovfl + char + sync
Error Code K: ovfl + dolr
Error Code L: ovfl + dolr + sync
Error Code M: ovfl + dolr + char
Error Code N: ovfl + dolr + char + sync
Error Code O: ovfl + lnfd
Error Code P: ovfl + lnfd + sync
Error Code Q: ovfl + lnfd + char
Error Code R: ovfl + lnfd + sync
Error Code S: ovfl + lnfd + dolr
Error Code T: ovfl + lnfd + dolr + sync
Error Code U: ovfl + lnfd + dolr + char
Error Code V: ovfl + lnfd + dolr + char + sync


Examples
$PNOLE,8,1
Depth input had one or more sync errors (most likely corrupted data).

$PNOLE,C,D
Depth and GPS inputs had one or more lnfd, dolr, and sync errors.

$PNOLE,1,G
Autopilot Input caused the combiner to overflow.


Notes
When attempting to isolate the source of PNOLE sentences, the obvious first place to look is at the input(s) reported in the sentence. Note, however, that in the case of overflow (ovfl) errors, the combiner may report the channel that finally overflows the buffer rather than the channel that is flooding the combiner with excess data.