Modify APB sentence Frequency

[keuponTed]

Hi everybody,


Is it possible to tune the APB sentence frequency send by openCPN via Serial Communication? I saw that the default frequency is 1Hz but I didn't find a setting to modify it.


Thanks!

[bdbcat]

keuponTed...
The 1 Hz APB frequency is hard coded.
Can you tell us more about your requirement for faster (or slower?) APB output?


Thanks
Dave

[keuponTed]

Thanks for the answer Dave.


I am developing my own autopilot and I use APB sentence to receive the route to follow (autopilot order). To detect the end of a route, I am using a timeout on APB sentence : when I don't receive it during 2s (2 APB frames), I stop my autopilot.


I would like to increase the APB frequency to reduce the timeout duration of my timer.


I hope it is sufficiently clear.
--

Ted

[stevead]

To detect the end of a route, why not use APB sentence fields 6 or 7 for the purpose they were intended ?

[keuponTed]

Dear Stevead,


Fields 6 and 7 of the APB sentence only give arrival to the target waypoint but what I need is the end of a route (multiple waypoints). So with these fields, I can't determine if I am at the end of the route or if I just reach one of the waypoints.


I see another solution which is to send the route to my autopilot with WPL sentences, but I have to make a lot of modifications on my autopilot software.


Best,
--

Ted

[bcn]

From the definition of APB:

[keuponTed]

Dear Bcn,


Please read my previous post.


I explained why I can't use these fields...


Best,

--

Ted

[seandepagnier]

What is the name of your autopilot?


It is not sensible to "timeout" for lack of APB, in this case it is expected the autopilot will hold the current route until such time another apb message is received.


the autopilot route plugin offers many more options for APB message generation compared to the core opencpn



a 1hz rate is adequate for nearly all applications, you would need a very agile or fast boat to benefit from higher rates.

[keuponTed]

Dear Seandepagnier,


The autopilot is a home made conception. I implemented a time out on APB sentence to know when I reach the end of the route.



I need metric precision for what I want to do, so 1 or 2 seconds at 5knots is prohibitive for my application.



The autopilot route plugin seems promising, but there is some issues with it :

- You can not see the actual target WP (blink in red/yellow in std OpenCPN)
- The range field in APB or RMB is not correctly fill.


Thanks!
--

Ted'

[bcn]

Ted..


as your application is "private" you might add a "dummy endpoint" to your route beyond the real end WP, with some special WP-ID like "end-of-route" or "9999999999", parsing for that to identify that you passed the final WP.


Out of curiosity: how do you achieve sub meter precision for position? Differential corrections in real time? From where? What type of GNSS receiver?



hubert

[keuponTed]

Dear bcn,


Thanks you very much for your answer. Create a dummy endpoint could be a good solution but I would like something "user-friendly" to create a new route. And I think, create new route and add a dummy way-point at the end is not an automatic procedure.


For sub-meter position, you could use differential or RTK GPS. For example, you have the hemisphere A222 which could work in DGNSS or RTK.


Ted'