Add GPS hardware version to MSP and optimize defaults for M8/M9/M10

[sensei-hacker]

User description

Summary

Extends MSP_GPSSTATISTICS to include GPS hardware version (hwVersion) for auto-detection, and updates GPS defaults for better out-of-box accuracy across all u-blox modules.

This enables the configurator to automatically detect GPS module type (M8/M9/M10) and apply optimal presets.

Changes

MSP Extension

• src/main/fc/fc_msp.c: Extended MSP_GPSSTATISTICS from 20 to 24 bytes to include gpsState.hwVersion
• docs/development/msp/msp_messages.json: Documented hwVersion field with value mappings (800=M8, 900=M9, 1000=M10, 0=Unknown)
• Backward compatible: Old configurators ignore the extra bytes

GPS Defaults

• gps_ublox_use_galileo: OFF → ON
• gps_ublox_use_beidou: OFF → ON
• gps_ublox_use_glonass: OFF (unchanged)
• gps_ublox_nav_hz: 10 → 8

Rationale for Defaults based on research on the u-blox forum, PX4 discussion, Clive Turvey (u-blox expert), and Jetrell's testing

• 8Hz rate allows M9 modules to use 32 satellites (vs 16 at ≥10Hz hardware limitation)
• 3 constellations (GPS+Galileo+Beidou) provide excellent global coverage
• Safe for all modules: M8 handles it easily, M9 gets full accuracy, M10 optimized at default clock
• Glonass OFF avoids unnecessary processing overhead, especially on M10

Updated gps_ublox_nav_hz description in settings.yaml to document M9's 16-satellite limitation at ≥10Hz.

Research & Citations

This work is based on research and community contributions:

u-blox Forum Research

• M9 16-satellite limitation
• u-blox forum posts documenting 10Hz threshold:
  • https://portal.u-blox.com/s/question/0D52p00008HKEbOCAX/can-neom9n-only-use-16-satellites-with-nav-update-rate-5hz
  • https://portal.u-blox.com/s/question/0D52p00009IsVqkCAF/is-the-neom9n-limited-to-16-svs-for-the-navigation-solution
  • https://portal.u-blox.com/s/question/0D52p0000990yQ1CAI/neom9n-reduced-satellites-at-increased-rates-is-there-a-way-around-it

Clive Turvey's Code Analysis

• Documented undocumented configuration key CFG-NAVSPG-CONSTR_GNSS (0x20110011 / 0xD5)
• Code: https://github.com/cturvey/RandomNinjaChef/blob/main/M9_channels.c
• Shows M9 hardware enforces 16-sat limit at ≥10Hz, 32-sat below 10Hz

PX4 GPS Driver Decision

• PX4 GPS drivers chose 5Hz for M9 for better accuracy (32 satellites)
• PR discussion: u-blox: reduce update rate for M9N to 5Hz (instead of 10Hz) PX4/PX4-GPSDrivers#57
• Confirms industry consensus on prioritizing accuracy over latency

Field Testing

• Jetrell's INAV testing contributed to understanding real-world M9 behavior
• Community-reported HDOP improvements: ~1.0-1.3 at 5Hz vs ~2.0-2.5 at 10Hz

Testing

Tested ✅

• Build: AOCODARCF4V3_SD target compiles successfully
• Flash: Firmware flashes and boots correctly
• MSP Extension: hwVersion field correctly reports 800 for M8 module
• Backward Compatibility: Old configurators work with extended message
• Settings: New defaults apply correctly on fresh config

Testing Needed ⚠️

• M9 modules: Community testing needed to verify hwVersion=900 detection
• M10 modules: Community testing needed to verify hwVersion=1000 detection
• Satellite tracking: Verify M9 actually uses 32 sats at 8Hz vs 16 at 10Hz
• Various GPS modules: Test with different M8/M9/M10 variants

Related PR

• Configurator PR: [will be linked after configurator PR is created]
• The configurator PR adds preset UI with auto-detection using this hwVersion field

Documentation

• Updated Settings.md (auto-generated from settings.yaml)
• MSP message documentation in msp_messages.json

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Testing help appreciated! If you have M9 or M10 modules connected, please test and report auto-detection

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PR Type

Enhancement

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Description

• Extend MSP_GPSSTATISTICS with GPS hardware version field

  • Add hwVersion field for auto-detection of M8/M9/M10 modules
  • Backward compatible with existing configurators

• Optimize GPS defaults for improved accuracy across all u-blox modules

  • Change gps_ublox_nav_hz from 10Hz to 8Hz (enables 32 satellites on M9)
  • Enable Galileo and Beidou constellations by default
  • Provides 3-constellation coverage for better global positioning

• Document M9 satellite limitation and rationale in settings

  • M9 limited to 16 satellites at ≥10Hz, 32 satellites below 10Hz
  • 8Hz default balances accuracy and latency across M8/M9/M10

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Diagram Walkthrough

flowchart LR
  A["MSP_GPSSTATISTICS<br/>Extended Message"] -->|"Add hwVersion<br/>field"| B["GPS Module<br/>Auto-detection"]
  C["GPS Defaults<br/>Configuration"] -->|"8Hz rate<br/>3 constellations"| D["Improved Accuracy<br/>M8/M9/M10"]
  B -->|"Enables"| E["Configurator<br/>Preset UI"]
  D -->|"Supports"| E

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File Walkthrough

	Relevant files
Enhancement	fc_msp.c Add hwVersion field to MSP_GPSSTATISTICS                                  src/main/fc/fc_msp.c Add sbufWriteU32(dst, gpsState.hwVersion) to MSP_GPSSTATISTICS message Extends message from 20 to 24 bytes with hardware version field Maintains backward compatibility with existing configurators +1/-0
Documentation	msp_messages.json Document GPS hardware version field in MSP                              docs/development/msp/msp_messages.json Document new hwVersion field in MSP_GPSSTATISTICS (message 166) Define version code mappings (500=UBLOX5, 600=UBLOX6, 700=UBLOX7, 800=UBLOX8, 900=UBLOX9, 1000=UBLOX10, 0=UNKNOWN) Specify field type as uint32_t with units as "Version code" +6/-0      Settings.md Update GPS settings documentation with new defaults            docs/Settings.md Update gps_ublox_nav_hz default value from 10 to 8 in table Expand description with M9 16-satellite limitation at ≥10Hz Document 32-satellite capability below 10Hz for better accuracy Update gps_ublox_use_beidou default from OFF to ON Update gps_ublox_use_galileo default from OFF to ON +4/-4
Configuration changes	settings.yaml Update GPS defaults and navigation rate documentation        src/main/fc/settings.yaml Change gps_ublox_nav_hz default from 10 to 8 Hz Enable gps_ublox_use_galileo by default (OFF → ON) Enable gps_ublox_use_beidou by default (OFF → ON) Update gps_ublox_nav_hz description with M9 satellite limitation details +4/-4

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[qodo-code-review]

PR Compliance Guide 🔍

All compliance sections have been disabled in the configurations.

[qodo-code-review]

Suggestion: Gate the new hwVersion field behind an explicit buffer/feature check (or protocol/version check) so legacy/size-assuming consumers don't break and serialization can't overrun a constrained buffer. [Learned best practice, importance: 6]

Suggested change

	sbufWriteU16(dst, gpsSol.hdop);
	sbufWriteU16(dst, gpsSol.eph);
	sbufWriteU16(dst, gpsSol.epv);
	sbufWriteU32(dst, gpsState.hwVersion);
	sbufWriteU16(dst, gpsSol.hdop);
	sbufWriteU16(dst, gpsSol.eph);
	sbufWriteU16(dst, gpsSol.epv);
	if (sbufBytesRemaining(dst) >= 4) {
	sbufWriteU32(dst, gpsState.hwVersion);
	}