Possible use when the autopilot is old and does not receive heading (true or magnetic). In NMEAconverter create a HDG (compass) sentence from your COG.
NMEA CHECKSUM ZIP
etc.Īs seen above, the $XXMTA sentence is sent each time a $WIMDA sentence is received and read by Dashboard.įor testing use VDR_pi or VDRplayer and run WIMDA+OCMDA.txt from this zip 4. Where $WIMDA5 is replaced by the 5th field of the $WIMDA sentence. Note that the data needed is in fields 5 and 6 of the MDA sentence. To get the data, Dashboard needs an $xxMTA sentence, however I had a Airmar PB200 unit that is sending $xxMDA sentences. The reason I wrote this plugin was I wanted Dashboard to show the air temperature. The real power of this plugin is that you can change the data of the sent sentence by cherry picking from incoming sentences. Setting the data to ignore will not affect the converter, the data will still be received there, it simply prevents the display of the data in OpenCPN.įor Reference from the NMEA Sentences Page, sentences that can be displayed in OpenCPN include: If you are making unit conversions, for instance, and do not ignore the original data you will end up with a display that flashes between the original value and the converted value. You do not need to add the end delimiter (*) or the checksum in your converter definitions - the converter will calculate the checksum and add the delimiter and checksum automatically.ĭepending on the data you are manipulating you may want to go into the OpenCPN Connections Tab and tell OpenCPN to ignore the original data. Once a conversion is defined you can select whether to send the calculated sentence on a fixed timing (every x seconds) or only when the incoming data is updated. Every time the plugin evaluates it will see its own creation, because of the wildcard it will reevaluate, … $XXHDG, $?HDG3,….) you will create a loop that will crash the plugin (and OpenCPN). If you create a conversion that outputs the same sentence as any field used in the input (e.g. Be careful when using wildcards and the talker ID, especially when correcting malformed sentences. $?HDG3 will retrieve the third field from any HDG sentence regardless of sender). The wildcard “?” at the front of an argument will tell the converter to use data from any talker sending the requested sentence (e.g. When inserting argument fields the wildcard “?” can be used to tell the converter to use data with any content where the “?” appears.
A number of detailed examples are provided below for reference. You must build a complete version of the sentence you want to send, and put the right data/fields from the original source in the right places for the converter to work properly. Use the NMEA Sentences Page to figure out what sentence you want to send, what data fields are required, and how the fields are configured.
In the simplest form an argument is an incoming NMEA sentence and field number - $GPRMC4 will get the fourth value in any RMC sentence received by OpenCPN from talker GP. A simple conversion example - this sample takes the 5th and 6th fields of an MDA sentence and transmits a new MTA sentence:Īrguments can take the form of constants (numeric or text), values from an incoming NMEA sentence, or calculations using either or both constants and incoming data. YYY is the NMEA sentence identifier you would like to send.
NMEA CHECKSUM MANUAL
The examples in this manual generally use XX as the talker ID for newly created sentences. NewSentence = $IDYYY where ID is a talker ID you would like to use to denote sentences from the converter. NewSentence, Argument for Field 1, Argument for Field 2. The basic format of a conversion command is:
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