Development

Selected build time options

Option	Values	Description
DFPLAYER	NO/YES	Enable DFPlayer Voice support (1.11.0+)
FLYSKY_GIMBAL	NO/YES	Enable FlySky FS-HZCZ03-ADJ gimbal support (1.11.0+)
PCBI6X_ELRS	NO/YES	Enable ExpressLRS/CRSF configuration tool (LUA alternative)
PCBI6X_INAV	NO/YES	Enable INAV Lite radar screen
PCBI6X_HELLO	NO/YES	Example "Hello World" radio tool to help developers to create their own
USB_SERIAL	NO/YES	Enable USB Serial modes - Telemetry mirror or debug in DEBUG build.
USB_MSD	NO/YES	Enable USB Mass Storage mode.
AFHDS2A_LQI_CH	1-17	Injects RSSI at channel, disabled by default
SBUS_TRAINER	NO/YES	Enable SBUS Trainer mode and trainer connected/disconnected sounds. (2.0.0+)
CRSF_FULLDUPLEX	NO/YES	Enable CRSF full duplex mode with RX pin at PA15 pad. Removes inversion. Use with i.e.: ELRS RX as TX configuration. (2.0.0+)
CRSF_EXTENDED_TYPES	NO/YES	Enable CRSF configuration parameters STRING and FLOAT types support.
FAKE_RSSI	NO/YES	Converts TRSS to RSSI data for receivers not sending RSSI.
EXTPWR_INVERT	NO/YES	Invert ext module power pin PC13 to allow use of P-MOSFET. (1.12.0+)
MENU_DIAG_ANAS_KEYS	NO/YES	Enable Keys and analogs diagnostics screens
DEBUG	NO/YES	Enable DEBUG serial output
GVARS	NO/YES	Enable Global Variables
HELI	NO/YES	Enable Heli menu

Compile

Example command:

docker run --rm -it -e "BOARD_NAME=i6x" -e "CMAKE_FLAGS=PCB=I6X HELI=NO GVARS=YES PCBI6X_INAV=NO PCBI6X_ELRS=YES DFPLAYER=YES USB_MSD=YES USB_SERIAL=YES SBUS_TRAINER=YES TRANSLATIONS=EN DEBUG=NO" -v ${PWD}:/opentx ajjjjjjjj/opentx-docker-i6x

Docker images:

• ajjjjjjjj/opentx-docker-i6x - to compile using recent GCC version with LTO, this is current default.
• vitass/opentx-fw-build - to compile older versions (1.8.0 and older) using GCC 4.7.

Flash

ST-Link is not required, you can flash using DFU mode without any additional hardware, but here is the ST-Link pinout.

ST-Link: sudo st-flash write firmware.bin 0x08000000

STM32 USB DFU Mode: dfu-util -a0 -s 0x08000000:leave -d 0483:df11 -D firmware.bin

APM32 USB DFU Mode: dfu-util -a0 -s 0x08000000:leave -d 314b:0106 -D firmware.bin

Debug port

Use USB Serial mode for debug log or AUX Serial port TX located at PA9 PCB pad. Serial port runs @115200 bauds, 8N1.

STM32F072 hardware mappings

GPIO / Exposed pads

Pad label	AF	Usage
PA9	USART1_TX	AUX Serial TX
PA10	USART1_RX	AUX Serial RX
PB8	TIM16_CH1, I2C1_SCL
PB9	TIM17_CH1, I2C1_SDA
TX2 (PD5)	USART2_TX	CRSF/Telemetry TX
PA15	USART2_RX	CRSF/Telemetry RX (CRSF_FULLDUPLEX mode)
PC9	TIM3_CH4	Backlight PWM
PC12	No useful AF
PC13	No AF	EXTMODULE Power switch
PC14	No AF	DFPlayer BUSY
PC15	No AF
PD0	SPI2_NSS (Slave select)
PD1	SPI2_SCK (Clock)
PD3	SPI2_MISO (Out)
PD4	SPI2_MOSI (In)
PD11	No useful AF
PF9	TIM15_CH1	PPM IN
PF10	TIM15_CH2	PPM OUT
TXD4	USART3/4_TX	AUX3 Serial TX - DFPlayer RX
RXD4	USART3/4_RX	AUX4 Serial RX - FS-HZCZ03-ADJ Gimbal TX

DMA

Channel	Mapping	Usage
1	ADC	ADC
2	TX1, TX3, SPI1_RX
3	RX1, RX3, SPI1_TX	AUX Serial RX (USART1)
4	TX1, TX2, SPI2_RX	Telemetry TX DMA (TX2) (USART2)
5	RX1, RX2, SPI2_TX	Telemetry RX DMA (RX2) (USART2)
6	RX2, RX3, RX4, SPI2_RX	AUX4 Serial RX (USART4)
7	TX2, TX3, TX4, SPI2_TX

Timers

Timer	Usage
TIM1	Buzzer PWM
TIM2
TIM3	BACKLIGHT_TIMER PWM
TIM6	STM32F0 delays
TIM7	TIMER_2MHz
TIM14	INTERRUPT_xMS
TIM15	EXTMODULE_TIMER (PPM + Trainer)
TIM16	INTMODULE_TIMER
TIM17	MIXER_SCHEDULER

NVIC priorities

Cortex-M0 (2 bits)	Cortex-M3/4 (4 bits)
0	0
1	1
2	2-6
3	7-15