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Flarm data / checksum error causes exit from navigation mode on Android


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Alastair Mutch
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I'm using 3.13.3.0 on an Android tablet - Samsung S2 - with data from a Powerflarm via an Airconnect wifi interface. 

A couple of times now I've got a pop-up dialogue saying "Flarm data invalid" along with a flarm data string displayed. Clicking to acknowledge this results in the program going back to planning mode.  This has happened on the ground before take-off only and not in the air (so far at least).

Interesting enough I was playing with the set-up in the house with both the tablet and my PC connected to the Airconnect and Skydemon running in navigation mode on both.  Both were using the current latest version - 3.13.3  When I got the error on the tablet the PC continued quite happily with the data with no errors.

If it is a checksum error on a data sentence please, please, please could you just dump that sentence and continue on to the next. I don't really want to know about what is probably a single bit error in the data transfer.  If there are multiple or frequent errors then by all means put up a warning or refuse to use the data stream.  Yes it shouldn't go wrong... but it obviously can do. 

Thanks.

Alastair


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Alastair Mutch
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Alastair Mutch - 1/20/2020 7:47:28 PM
Alastair Mutch - 1/20/2020 5:03:40 PM
Alastair Mutch - 1/20/2020 1:57:16 PM
Tim Dawson - 1/20/2020 10:42:23 AM
Could you please post a screenshot or the exact error you saw? "Flarm data invalid" is not a message in SkyDemon so we don't know exactly what is happening from your post.

We do not halt navigation mode on receipt of an invalid checksum.

Sorry you are right. I mis-remembered the exact error message.  It was actually "Unexpected GPS data encountered:" Here is the screen dump. It looks like a block of data has got lost somewhere. 

Build is 16732
Anyway it dumps Skydemon out of Nav mode and I can reproduce it but just leaving it sitting in navigation mode static on the ground. 
The extra error messages regarding lack in internet connection appear after the error has occurred and it has dropped back into planning mode.  The wifi connection is still up when the error occurs. 

Regards,
Alastair 

Hmmm....
When I connect to the airconnect wifi with my PC and capture the port 2000 data output to a log file using telnet I can see frequent data errors in the data stream due to what looks like missing bytes / blocks of data..   I'll investigate further to see what my actual problem is.  This is with a single device connect to the airconnect and the serial interface from flarm to airconnect only runnng at 19200baud. 

If it is possible to get Skydemon to not exit navigation mode on a datastream error that would still be good.

Alastair


I fixed it by increasing the serial interface speed between the Flarm and Airconnect from 19k2 up to the maximum of 56k7 baud. It looks like a problem in the Flarm firmware in how it handles multiple messages getting queued up when it gets busy.  I'm on the approach ot Edinburgh airport so the rate of messages increases when Mode C / ADSB stuff is going past but it should still be able to handle the data at 19k2 but seems to be overwriting buffers or FIFO data. There are warnings in the flarm manual about losing data if there are too many messages for the baud rate. .  
. .  
I've left it running for an hour whilst monitoring the data on my PC and it all looks good - no missing data.  Problem solved.  

Alastair


I spoke too soon. I got an Unexpected GPS error after a couple of hours.  The data stream looks clean and I can't spot the error in the log file captured on the PC but obviously it still has a very occasional error GPS sentence.   

Any chance of getting this handled less "hard" in Skydemon please? 

I don't have any expectation of the Flarm firmware getting improved to completely eliminate the error - assuming that is the source.  One error in the data stream every couple of hours is not ideal but the current handling of the error is likely to cause more problem than the data error itself. 

Alastair


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Alastair Mutch - 1/18/2020 7:29:57 PM
Tim Dawson - 1/20/2020 10:42:23 AM
Alastair Mutch - 1/20/2020 1:57:16 PM
Alastair Mutch - 1/20/2020 5:03:40 PM
Alastair Mutch - 1/20/2020 7:47:28 PM
                         I spoke too soon. I got an Unexpected GPS error after a couple of...
Alastair Mutch - 1/20/2020 10:07:02 PM
Tim Dawson - 1/21/2020 11:01:59 AM
Alastair Mutch - 1/21/2020 12:21:15 PM
Tim Dawson - 1/23/2020 11:19:10 AM
Alastair Mutch - 1/23/2020 1:18:06 PM
Alastair Mutch - 1/24/2020 7:54:17 PM
Tim Dawson - 1/24/2020 12:16:15 PM
Alastair Mutch - 1/24/2020 8:00:59 PM
Alastair Mutch - 1/24/2020 8:30:55 PM
Tim Dawson - 1/27/2020 12:11:51 PM
Alastair Mutch - 1/27/2020 2:27:58 PM
ken@blackman.co.uk - 2/4/2020 1:27:56 PM
ken@blackman.co.uk - 2/4/2020 1:29:30 PM
Alastair Mutch - 2/4/2020 7:21:31 PM
tarutino - 3/20/2020 7:40:00 AM
Alastair Mutch - 3/20/2020 10:13:27 AM
                         Hello Alastair, thank you very much for your Description. I have...
tarutino - 3/23/2020 2:43:39 PM
                         Dear Alastair, I have been struggling with the same data transfer...
Europa XS - 6/1/2020 10:35:18 AM
                             Dear Herbert, The instructions are dependant on the type of Wifi unit...
Alastair Mutch - 6/1/2020 1:34:31 PM
ken@blackman.co.uk - 3/20/2020 11:50:25 AM
Tim Dawson - 3/23/2020 11:38:27 AM
Alastair Mutch - 3/23/2020 11:42:32 AM
ken@blackman.co.uk - 3/23/2020 2:56:21 PM
                 Hi Ken, which firmware is on your PF Portable?
Fliegerpeer - 5/5/2020 10:08:07 AM
ken@blackman.co.uk - 5/18/2020 12:38:17 PM

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