M9N GPS is limited to 16 sats with 1.16

PX4 Autopilot
1

PX4 1.16, holybro M9N GPS with holybro pixhawk 6c mini and 6x, m9N can see only 16 sats. But with 1.15.4 and earlier it can easily go up to 26. Is it now something configurable / limiting the number of sats or an issue?

2

nothing has changed in the ubx driver, are you sure it’s related to the version?

3

yes, after seeing this, verified with fw 1.15.4 and 1.16 back’n forth multiple times. Both on 6CMini and 6X. definetly px4 firmware.

4

@AlexKlimaj any ideas?

5

I think the issue lays in the PX4 source code. Searching for the reason behind my inability to increase the update rate of my GPS to a higher Hz value I looked in the source code and this seems to fit your problem (Path: PX4-GPSDrivers/src/ubx.ccp

// measurement rate
// F9P L1L2 in firmware <1.50 the max update rate with 4 constellations is 9Hz without RTK and 7Hz with RTK
// F9P L1L2 in firmware >=1.50 the max update rate with 4 constellations is 7Hz without RTK and 5Hz with RTK
// F9P L1L5 the max update rate with 4 constellations is 8Hz without RTK and 7Hz with RTK
// DAN-F10N the max update rate is 10Hz with GPS+GAL+BDS(Default)
// Receivers such as M9N and DAN-F10N can go higher than 10Hz, but the number of used satellites will be restricted to 16. (Not mentioned in datasheet)
int rate_meas = 100; // 10Hz

switch (_board) {
case Board::u_blox9_F9P_L1L2:
	rate_meas = 200; // 5Hz
	break;

case Board::u_blox9_F9P_L1L5:
	rate_meas = 143; // 7Hz
	break;

case Board::u_blox_X20:
	rate_meas = 40; // 25Hz

default:
	break;
6

I have implemented a fix. We will get it tested tomorrow.

7

@Mu_De this is now fixed in main, thanks for the report

8

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