New Plugin NmeaConvertor

[rgleason]

PS: What seatalk converter do you have?

[Viking Sailor]

Originally Posted by RhythmDoctor

You can use that if you prefer. But two years from now, when something breaks and I'm trying to figure out wth I was doing, or if someone else is trying to figure out what I was doing, -180/3.14159265 is immediately recognizable as the needed conversion between degrees and radians. Sometimes the fewest keystrokes is not the cleanest code.

That's the same reason I used the unfactored Pythagorean theorem, instead of trying to reduce the terms using cos^2(x)+sin^2(x)=1 (like my trigonometry teacher would have demanded). It's just easier to see and debug.

Sorry!

I just thought you didn't know any better and didn't want you to look like a fool.

[RhythmDoctor]

Originally Posted by Viking Sailor

Sorry!

I just thought you didn't know any better and didn't want you to look like a fool.

No problem, your suggestion is fine. It’s all a matter of preference. Wouldn’t be the first time I looked like a fool. Nice to know you’ve got my back!

I’ll respond to the others’ questions later when I have more time.

[transmitterdan]

The rad and deg functions are part of the package. You can test by using a formula of deg(rad(90))

It should produce pretty close to 90.0.

[RhythmDoctor]

Originally Posted by rgleason

PS: What seatalk converter do you have?

vYacht router (Seatalk+NMEA0183 version). It's since been replaced by a version that also speaks NMEA2000. https://vyacht.net/

Originally Posted by transmitterdan

The rad and deg functions are part of the package. You can test by using a formula of deg(rad(90))

It should produce pretty close to 90.0.

Thanks for the tip! Here are the new/improved equations:

Generic variables:

TWA=90-deg(atan((AWS*cos(rad(AWA))-SOG)/AWS*sin(rad(AWA))))

TWS=sqrt(sqr(AWS*sin(rad(AWA)))+sqr(AWS*cos(rad(AW A))-SOG))

Seatalk - vYacht dialect:

TWA=90-deg(atan(($GPVWR3*cos(rad($GPVWR1))-$GPRMC7)/$GPVWR3*sin(rad($GPVWR1))))

TWS=sqrt(sqr($GPVWR3*sin(rad($GPVWR1)))+sqr($GPVWR 3*cos(rad($GPVWR1))-$GPRMC7))

NmeaConverter Sentences

Seatalk - vYacht dialect:

$XXVWT,90-deg(atan(($GPVWR3*cos(rad($GPVWR1))-$GPRMC7)/$GPVWR3*sin(rad($GPVWR1)))),$GPVWR2,sqrt(sqr($GPVW R3*sin(rad($GPVWR1)))+sqr($GPVWR3*cos(rad($GPVWR1) )-$GPRMC7)),$GPVWR4,,,,<return>

ZZZ’s dialect (Simrad?):

$XXMWV,90-deg(atan(($WIMWV3*cos(rad($WIMWV1))-$GPRMC7)/$WIMWV3*sin(rad($WIMWV1)))),T,sqrt(sqr($WIMWV3*sin (rad($WIMWV1)))+sqr($WIMWV3*cos(rad($WIMWV1))-$GPRMC7)),N,A

[transmitterdan]

Here is a list of all functions supported by the underlying equation engine:

 *  Math functions
 *      - abs : the absolute value, it removes the sign
 *      - ceil : the smallest integer greater than or equal to x
 *      - cub : x^3, safe way to compute such an exponent
 *      - deg : converts from radian to degree
 *      - exp : the exponential value
 *      - hvi : Heaviside's function, =0 if x<0, =1 if x>=0
 *      - int : the largest integer less than or equal to x
 *      - inv : inverts, 1/x
 *      - ln : the neperian logarithm
 *      - log : the logarithm base 10
 *      - rad : converts from degree to radian
 *      - sgn : the sign, -1 or +1. Zero returns +1.
 *      - sqr : x^2, safe way to compute such an exponent
 *      - sqrt : the root square
 *
 *  Trigonometric functions
 *      - acos : the secant (inverse of cosine)
 *      - acsh : the inverse of the hyperbolic cosine
 *      - asin : the cosecant (inverse of sine)
 *      - asnh : the inverse of the hyperbolic sine
 *      - atan : the cotangent (inverse of tangent)
 *      - atnh : the inverse of the hyperbolic tangent
 *      - cos : the cosine
 *      - cosh : the hyperbolic cosine
 *      - sin : the sine
 *      - sinc : the cardinal sine (radian)
 *      - sinh : the hyperbolic sine
 *      - tan : the tangent
 *      - tanh : the hyperbolic tangent

[RhythmDoctor]

Originally Posted by RhythmDoctor

NmeaConverter Sentences

...

ZZZ’s dialect (Simrad?):

$XXMWV,90-deg(atan(($WIMWV3*cos(rad($WIMWV1))-$GPRMC7)/$WIMWV3*sin(rad($WIMWV1)))),T,sqrt(sqr($WIMWV3*sin (rad($WIMWV1)))+sqr($WIMWV3*cos(rad($WIMWV1))-$GPRMC7)),N,A

I forgot to mention: I have not tested this revision of ZZZ's sentence, since I don't have the right VDR script. It would be good if someone else tested it.

[RhythmDoctor]

Originally Posted by RhythmDoctor

I forgot to mention: I have not tested this revision of ZZZ's sentence, since I don't have the right VDR script. It would be good if someone else tested it.

After some additional work tonight, I am concerned that this sentence in ZZZ's "dialect" of NMEA will fail except in certain quadrants of wind direction. The (obsolete) VWR and VWT sentences report angles from 0-180 with an additional parameter for L (left) or R (right). Fortunately, the Dashboard plugin recognized this and displays correctly.

But the newer MWV sentence syntax reports direction as 0-360° with no L or R provided. This creates a uniqueness issue for any use of the atan() function. tan(45°) =1. But tan (225°)=1 also. Conversely, atan(1) could be 45° or 225°. The answer is not unique without further information on the quadrant (such as L or R, which is provided by the obsolete VWR/VWT sentences).

Maybe this is why ZZZ's equation worked for others, but not for me (although the value > 1 within the atan() function still raises alarm bells). Perhaps my equation works for the obsolete VWR/VWT sentences, but ZZZ's equation is needed for MWV sentences.

Eventually, I suggest that examples of both types of sentences be included in the Wiki, but only after further testing. That testing must be sure to include wind angles from all four quadrants for a complete test.

[RhythmDoctor]

By the way, I found an error in the wiki for NmeaConverter:

3. Do math-Convert units, e.g. Centigrade to Fahrenheit
But what if I was living in the US and prefered the reading to be in degrees Fahrenheit? Just change the format to:

$XXMTA, 5 / 9 * $WIMDA5 + 32, F

The equation should be 9/5, not 5/9. Also, I suggest taking out the excess spaces, since that may cause problems of people paste the equation in to the plugin.

I'd make this change myself, but my login no longer works.

[knowconcept]

I am trying to show the Leeway (field2 of VMVBW) value as a DPT instrument. I setup NMEAConverter like this: $XXDPT,VMVBW2 The NMEAConverter shows the values updating, but when i set a Depth gauge up in OpenCPN I get no data. Any idea what I am doing wrong?

Thanks!

[bcn]

Rhythmdoctor,

done,

and btw.: the formula is correct in the window of the Wiki screenshot..

[RhythmDoctor]

Originally Posted by knowconcept

I am trying to show the Leeway (field2 of VMVBW) value as a DPT instrument. I setup NMEAConverter like this: $XXDPT,VMVBW2 The NMEAConverter shows the values updating, but when i set a Depth gauge up in OpenCPN I get no data. Any idea what I am doing wrong?

Thanks!

My tranducer puts out DBT, not DPT, so take this with a grain of salt:

DBT sentences have additional parameters that indicate units. For example:

$GPDBT,47.90,f,14.60,M,,

It's possible that without a valid parameter to indicate units, O will not display it.

It might be totally different for DPT, but I'd first try to enter units. Of course, if you enter N (typical abbreviation for kNots), it might refuse to accept it, since that's not a valid depth unit.

[knowconcept]

Awesome and Thank you! It required the entire sentence which makes sense. This is what I did: $XXDBT,1.1,f,VMVBW2,M,3.3,F

[transmitterdan]

DBT means depth below transducer. An offset is needed to get water depth from the surface (DPT). Just FYI.

O should display DPT if it is available.

[RhythmDoctor]

Originally Posted by transmitterdan

DBT means depth below transducer. An offset is needed to get water depth from the surface (DPT). Just FYI.

O should display DPT if it is available.

Yes, I am aware of that, DBT and DPT are different things, as I pointed out. My SeaTalk network is only reporting DBT at this time.

I have an offset programmed into the depth instrument, but it’s not reporting DPT on Seatalk. I can make my autopilot display depth, and it shows the value corrected for offset, so the DPT value is definitely going onto SeaTalk network (otherwise the autopilot wouldn’t display it), but I think it’s reporting the DPT value in the DBT sentence.

I’ll have to wait until the boat is in the water before I figure this out.