AP_GPS: Remove external event from Septentrio driver #11025
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khancyr
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Apr 12, 2019
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Testred it today, worked fine. |
amilcarlucas
approved these changes
Apr 12, 2019
If the event pin floats, this can lead to UART congestion, causing the EKF to reject the GPS data, and the vehicle will drift around the sky in a most disturbing manner
This improves log analysis of bad GPS health messages when you have a report of bad GPS health but lost the MAVLink message, or didn't have access to the autopilot log with the information for some reason.
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This was on the list to backport to Rover-3.5 but I hit significant merge conflicts so I'll leave it to Rover-3.6 unless there are objections |
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@rmackay9 I'd object given that if this happens the EKF will be rejecting all GPS data until the situation recovers, which could be a undefined time period. |
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@WickedShell, any chance that you could create a PR or just merge it to the Rover-3.5 branch? Sorry to put extra load on your but I just don't trust myself to get it right.. |
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The Septentrio driver was logging camera feedback that the GPS witnessed. This was useful from a minimum hardware perspective, but it does pose a safety risk to flight. If to many events are triggered (due to noise on the input pin, or a truly fast camera) you can create congestion on the serial port to the GPS and the position data gets delayed. We detect this in the health bits, but the lag the data experiences becomes significant enough that the EKF will start rejecting the GPS data. This leads to oscillations in the sky, and all kinds of horrifying stuff happening. To correct for this I've removed the feedback into ArduPilot. I'm happy to restore it in the future if there is a patch on the GPS firmware that would prevent this from blocking the flight critical positioning data. As a note the GPS did detect the buffer overflow/port congestion, and we did detect it on the ArduPilot side. This does not have any impact on the PPK workflow, all events are still logged to the GPS SD card the same as they were before.
Example of external event induced lag (this line of timestamps should be perfectly flat, instead of bending in the middle):
This also makes a change to ensure that we log receiver status to the GPS SD card. This is useful for problem analysis, when the statustext message from the autopilot gets lost, or the user has misplaced the log files.
This was test flown on a AsteRx-M2
@amilcarlucas this patch may be of interest to you.