AP_Compass: add IIS2MDC driver

[dakejahl]

Adds a driver for the ST IIS2MDC magnetometer
https://www.st.com/resource/en/datasheet/iis2mdc.pdf

[peterbarker]

Please fold the commits.

Please also outline the testing you've done.

[dakejahl]

Please fold the commits.

Done. Should I do a separate commit for Tools/? I assumed a single commit since this PR should be atomic.

Please also outline the testing you've done.

Bench tested on the ARK FPV. I've uploaded the log file to Drive.

QGC

PlotJuggler

[dakejahl]

@peterbarker can you let me know if there's anything else here you'd like to see?

[dakejahl]

Is there anything else needed to get this merged? The ARK FPV board support depends on it.

I've also uploaded a flight log in position mode demonstrating functionality
#28603 (comment)

[peterbarker]

LGTM apart from the minor include issue

[dakejahl]

BTW, this driver will also work for the LIS2MDL. Just discovered this while doing a betaflight port board. ST says that this is basically just a better version of the LIS2MDL

LIS2MDL, IIS2MDC, LSM303AGR and LSM303AH are firmware and pin-to-pin compatible solutions

https://www.st.com/resource/en/design_tip/dt0131-digital-magnetometer-and-ecompass-efficient-design-tips--stmicroelectronics.pdf

[andyp1per]

Binary Name      Text [B]        Data [B]     BSS (B)        Total Flash Change [B] (%)      Flash Free After PR (B)
---------------  --------------  -----------  -------------  ----------------------------  -------------------------
arducopter-heli  996 (+0.0546%)  0 (0.0000%)  4 (+0.0015%)   996 (+0.0545%)                                   137060
antennatracker   996 (+0.0739%)  0 (0.0000%)  -4 (-0.0015%)  996 (+0.0738%)                                   614956
arducopter       996 (+0.0546%)  0 (0.0000%)  -4 (-0.0015%)  996 (+0.0544%)                                   135436
ardurover        996 (+0.0596%)  0 (0.0000%)  4 (+0.0015%)   996 (+0.0595%)                                   292164
arduplane        996 (+0.0550%)  0 (0.0000%)  4 (+0.0015%)   996 (+0.0549%)                                   149348
blimp            996 (+0.0727%)  0 (0.0000%)  -4 (-0.0015%)  996 (+0.0726%)                                   592608
ardusub          996 (+0.0617%)  0 (0.0000%)  -4 (-0.0015%)  996 (+0.0616%)                                   348032

This adds 1k to all the boards that include all the compasses, but none of them are using it. I think we should consider having this off by default or disabling by default one of the other compass drivers that is now little used.

[dakejahl]

@andyp1per does ardupilot have a mechanism to enable only certain drivers for a target? For example in PX4 uses Kconfig
https://github.com/PX4/PX4-Autopilot/blob/main/boards/ark/fpv/default.px4board#L17

[andyp1per]

@andyp1per does ardupilot have a mechanism to enable only certain drivers for a target? For example in PX4 uses Kconfig https://github.com/PX4/PX4-Autopilot/blob/main/boards/ark/fpv/default.px4board#L17

Yes, just define the backends you need -

ardupilot/libraries/AP_HAL_ChibiOS/hwdef/skyviper-v2450/hwdef.dat

Line 109 in 6095512

define AP_BARO_ICM20789_ENABLED 1

[dakejahl]

@andyp1per hmm it seems that I need to change both of these

Feature('Compass', 'IIS2MDC', 'AP_COMPASS_IIS2MDC_ENABLED', 'Enable IIS2MDC compasses', 0, None),

and

#ifndef AP_COMPASS_IIS2MDC_ENABLED
#define AP_COMPASS_IIS2MDC_ENABLED 0
#endif

which is a little strange since I would expect the latter to only be necessary if the former is missing. I noticed only changing the "Feature" to 0 (default disabled) still results in the .cpp being compiled

[dakejahl]

Re-tested on hardware functional.

[andyp1per]

Feature only affects custom build server.
File will be compiled regardless, but the lack of linkage means it will be elided

[dakejahl]

Okay, should I change one of these back to 1? Or does this look good to go?

[andyp1per]

Looks good to me

[peterbarker]

Merged, thanks!