H520E RTK - problem after repair

[polskipilot]

Welcome.
I have a H520E RTK drone, the drone is after a collision which resulted in the bracket being replaced so the drone required a full disassembly and reassembly and now unfortunately outside it is not catching satellites at all. There is an image, the camera starts up normally but there are messages like in the picture. The GPS is properly connected and unfortunately the drone cannot be started even in indoor mode (I am also sending pictures). I don't really have much idea where to start and check to start with?

 

[h-elsner]

It looks like the last mission hangs somehow in the system. The message has something to do with handling of waypoints. maybe this will be solved by itself if GPS is ready.

To check what is wrong with GPS please send us .TLOG files from ST16S from the last tries and the related .ULOG files from the drone.

 

[h-elsner]

One question that came in my mind when I see the error message from EKF status: Is the GPS module mounted in the same direction as it has had before?
I know from my Typhoon H that the arrow on the module is directed backwards, forward as I would expect.

 

[polskipilot]

The top case including the GPS was not damaged, so I just plugged in the board. The inner bracket was simply broken and that is why it was disassembled.
I am uploading the logs from the controller below as the drone is disassembled.

Dropbox

www.dropbox.com

.

 

[h-elsner]

I refer to the last log file from 28.03.2025. The EKF status is OK all the time. In the System Status the GPS is present (or with other words expected), not enabled and not healthy. For a short period of time the AHRS subsystem (Attitude Heading Reference System) is not healthy. The same time as the message about Yaw estimator comes. But this happens only in two MAVlink messages SYS_STATUS. I would not overestimate this.

But the missing GPS (no messages GPS_RAW_INT at all) is the real problem. The compass is on the same module and is present and healthy and we can read the X/Y/Z values from it. This tells me the GPS moldule is plugged in, power is supplied and the I²C bus is working. The GPS chip itself is connected via UART (not on I²C bus). Maybe the UART is defective or there is a problem with wiring.
Could you please check if there is no bent or broken pin ind the GPS plug? Sometimes a bent pin causes such problems. This is not so rare as we think. A magnifier would help to check this out.

 

[polskipilot]

Hello
I think I am already slowly running out of ingenuity. I'm uploading pics because it's already after swapping various GPS but still no effect, and I'm wondering if the motherboard in some module responsible for communication with the GPS is physically damaged. Does anyone perhaps have a technical diagram of the board for the H520 drone? When INDOOR MODE is switched on, everything is fine (propellers spin and it flies normally) while when switching to normal mode there is a message like in the picture and unfortunately the drone reports an error message. Does anyone have any ideas?

 

[h-elsner]

My only idea in this case is to look with an oscilloscope what is going on at Rx and Tx wire. As far as I know, Rx and Tx are directly connected to the processor pins usually with a resistor.

 

[polskipilot]

I have already swapped 2 different compasses and it is the same all the time (even from a working flying drone). Which UART is this and where is it located? In the picture there is a plug which seems good (all pins seem to be in place), there is also a picture of the board so if you zoom in you can see something worrying. The drone is after a crash. I'll still replace the wire connecting the drone to the motherboard later.

 

[h-elsner]

The UART is two wires from the six-wire cable to the GPS-module.
If the H520E has the same or similar GPS module then the location is as here labeled as Rx and Tx.


SCL and SDA belongs to the I²C bus to compass chip.
Rx and Tx belongs to the serial connection (UART) of the GPS chip.