[AT32F435] GREATMOUNTAINF435 Cloud Build compilation error in AT32 bus drivers

[bobberdolle1]

Description

Target GREATMOUNTAINF435 (AT32F435M MCU) fails to compile on the Betaflight Cloud Build server for versions 4.5.x and 2025.12.x.

Error Trace

make[2]: *** [Makefile:440: obj/main/AT32F435M_GREATMOUNTAINF435/drivers/at32/bus_i2c_atbsp.o] Error 1 cc1: all warnings being treated as errors make[2]: *** [Makefile:440: obj/main/AT32F435M_GREATMOUNTAINF435/drivers/at32/bus_spi_at32bsp.o] Error 1 make[1]: *** [Makefile:556: hex] Error 2 make: *** [mk/config.mk:62: GREATMOUNTAINF435] Error 2

Impact

Users attempting to flash GREATMOUNTAINF435 using Betaflight Configurator Cloud Build fail to compile or get missing drivers (e.g. ICM42688P gyro non-functional).

Proposed Fix

Fix the compiler warning in src/main/drivers/at32/bus_i2c_atbsp.c and src/main/drivers/at32/bus_spi_at32bsp.c or update configuration flags for AT32 bus initialization.

[haslinghuis]

[bobberdolle1]

Thanks @haslinghuis for checking!

The reason users with Great Mountain RGT7 boards experience a non-functional gyro when flashing the standard GREATMOUNTAINF435 target is due to the default IMU defines in configs/GMRC/GREATMOUNTAINF435/config.h:

c #define USE_ACCGYRO_BMI270 #define USE_ACC_SPI_ICM42688P #define USE_GYRO_SPI_ICM42688P #define GYRO_1_ALIGN CW180_DEG_FLIP

The retail Great Mountain AT32F435 RGT7 flight controller uses ICM42688P with CW270 alignment, whereas the default config specifies BMI270 and CW180_DEG_FLIP.

Would it be possible to update config.h in betaflight/config (or add a dedicated target definition GREATMOUNTAINF435_RGT7) so that Great Mountain RGT7 users get a working gyro and correct orientation out of the box without needing custom CLI configuration?

[haslinghuis]

Is this a new / other board re-using the same config? In that case a separate board config should be added.

@shanggl any info on this?

[bobberdolle1]

Yes, exactly. Great Mountain produces a few board variants (RGT7 = LQFP64 MCU, VMT7 = LQFP100 MCU). The RGT7 version uses ICM42688P with CW270 gyro alignment.

Adding a dedicated target definition GREATMOUNTAINF435_RGT7 with ICM42688P and CW270 orientation would give RGT7 users a working target out of the box.

[haslinghuis]

Links please :)

[bobberdolle1]

Here is the link to the official Chinese PDF manual for the Great Mountain AT32F435 RGT7 flight controller:

📄 Great_Mountain_AT32F435_RGT7_Manual.pdf

Key specs from the manual:

• MCU: AT32F435RGT7 (LQFP64)
• Gyro: ICM-42688-P (SPI1: CS PA4, EXTI PA15)
• Gyro Orientation: CW270 (Page 4 explicitly specifies CW270 alignment for Betaflight)
• Baro: DPS310 (I2C3: SCL PC0, SDA PC1)
• Flash: W25Q128 (SPI3: CS PD6)
• OSD: MAX7456 / AT7456 (SPI2: CS PD5)

[bobberdolle1]

Correction + verified pin map for the RGT7 board (follow-up to my earlier comment — please disregard the pins I posted there: they were copied from the VMT7 config and are wrong for this board; PD-port pins don't even exist on the LQFP64 package).

To get authoritative data I extracted the parameter-group reset defaults and the CLI resource table from the vendor's factory firmware (ATBF 4.3.4 fork, board name GREATMOUNTAINF435SS) and then verified the result on the actual hardware.

Verified result: the GreatMountain RGT7 board is pin-for-pin identical to the existing NEUTRONRCF435SE config (same open-source AT32 reference design). I flashed the NEUTRONRCF435SE 2025.12.5 cloud build on the RGT7 and everything works with zero CLI remapping: ICM-42688-P gyro, ADC (VBAT/CURR), W25Q128 blackbox flash, AT7456E OSD, UART1–5, LED strip, beeper, config save.

Actual RGT7 map (extracted from factory firmware, hardware-verified):

• MCU: AT32F435RGT7 (LQFP64, 1MB flash) → FC_TARGET_MCU AT32F435G
• Gyro ICM-42688-P: SPI1 (PA5/PA6/PA7), CS PA15, EXTI PA8, align CW180_DEG (default in the vendor 4.3.4 build; note the paper manual mentions CW270 for some 20×20 variants, so this may vary by revision/sub-model)
• Motors 1–4: PC9 / PC8 / PC7 / PC6
• Servo pads: PB6, PB7, PB1, PB0 (vendor dual-servo build also exposes PA0, PB8)
• Blackbox flash W25Q128: SPI3 (PB3/PB4/PB5), CS PB9
• OSD AT7456E: SPI2 (PB13/PB14/PB15), CS PB12
• UART1–5: PA9/PA10, PA2/PA3, PB10/PB11, PC10/PC11, PC12/PD2
• Baro DPS310: I2C2 PB10/PB11 (pads shared with UART3)
• ADC: VBAT PC2 (scale 110), CURR PC1
• LED strip PA1, status LED PC4, beeper PC15
• Vendor timer indexes (its timerIOConfig): PC9/PC8/PC7/PC6 idx 2, PA0 idx 2, PA1 idx 1, PB6/PB7 idx 1, PB1/PB0/PB8 idx 2

One more reason a dedicated config matters: flashing the existing GREATMOUNTAINF435 (AT32F435M) onto the RGT7 also breaks config persistence — save faults and the FC reboots into DFU, settings never stick, and ADC reads garbage (the M build keeps the config region beyond the RGT7's 1MB flash; the vendor's own 4.3.4 build stores config at 0x080FC000, inside 1MB). So RGT7 owners picking the target by board name currently get a non-working gyro and a board that can't save.

Suggestion: add GREATMOUNTAINF435RGT7 (manufacturer GMRC) as a duplicate of NEUTRONRCF435SE (AT32F435G) plus the servo pad defines above. I can open the PR against betaflight/config if that helps.

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