inav/docs/boards/NEXUSX.md

Radiomaster NEXUS X and NEXUS XR

Flight controllers originally designed for helicopters using Rotorflight. Based on STM32F722RET6. Both NEXUS X and XR share the same target in iNav.

Built-in peripherals

Both models contain a ICM42688P IMU, a SPL06 barometer and a W25N02KVZEIR blackbox memory chip.

The NEXUS XR also contains a serial ELRS receiver based on the RP4TD-M using ESP32 and two SX1281. It is connected to the main STM32F7 Flight Controller on UART5. None of the external connections route to the receiver, they are all connected to the STM32F7 Flight Controller. The receiver can be disabled using USER1, which controls a pinio on pin PC8.

Pin configuration

The RPM, TLM, AUX and SBUS pins are Servo/Motor outputs by default. However, when UART1 or UART2 are assigned a function in the ports tab, the pins will become a UART instead. See the table below.

Marking on the case	Both UART1 and UART2 unused	UART1 in use	UART2 in use	Both UART1 and UART2 in use
S1	Output S1	Output S1	Output S1	Output S1
S2	Output S2	Output S2	Output S2	Output S2
S3	Output S3	Output S3	Output S3	Output S3
TAIL	Output S4	Output S4	Output S4	Output S4
ESC	Output S5	Output S5	Output S5	Output S5
RPM	Output S6	Output S6	UART2 TX	UART2 TX
TLM	Output S7	Output S7	UART2 RX	UART2 RX
AUX	Output S8	UART1 TX	Output S6	UART1 TX
SBUS	Output S9	UART1 RX	Output S7	UART1 RX
A	UART4 pin order: TX, RX, 5V, GND	UART4 pin order: TX, RX, 5V, GND	UART4 pin order: TX, RX, 5V, GND	UART4 pin order: TX, RX, 5V, GND
B	UART6 pin order: TX, RX, 5V, GND	UART6 pin order: TX, RX, 5V, GND	UART6 pin order: TX, RX, 5V, GND	UART6 pin order: TX, RX, 5V, GND
C	I2C pin order: SCL, SDA, 5V, GND or UART3 pin order: TX, RX, 5V, GND	I2C pin order: SCL, SDA, 5V, GND or UART3 pin order: TX, RX, 5V, GND	I2C pin order: SCL, SDA, 5V, GND or UART3 pin order: TX, RX, 5V, GND	I2C pin order: SCL, SDA, 5V, GND or UART3 pin order: TX, RX, 5V, GND
EXT-V	battery voltage max 60V pin order: Vbat, GND	battery voltage max 60V pin order: Vbat, GND	battery voltage max 60V pin order: Vbat, GND	battery voltage max 60V pin order: Vbat, GND
built-in ELRS	UART5	UART5	UART5	UART5

All pin orders are from left to right, when looking at the connector on the flight controller. Note that the pin order for "A", "B" and "C" is incorrect on radiomaster's website, it has RX and TX swapped.

Hardware layout

Marking on the case	STM32 pin	Servo	UART	I2C
S1	PB4	TIM3CH1	n/a	n/a
S2	PB5	TIM3CH2	n/a	n/a
S3	PB0	TIM3CH3	n/a	n/a
TAIL	PA15	TIM2CH1	n/a	n/a
ESC	PA9	TIM1CH2	UART1 TX	n/a
RPM	PA2	TIM2CH3 TIM5CH3 TIM9CH1	UART2 TX	n/a
TLM	PA3	TIM2CH4 TIM5CH4 TIM9CH2	UART2 RX	n/a
AUX	PB6	TIM4CH1	UART1 TX	I2C1 SCL
SBUS	PB7	TIM4CH2	UART1 RX	I2C1 SDA
A	PA1/PA0	TIM1 TIM5	UART2 UART4	n/a
B	PC7/PC6	TIM3 TIM8	UART6	n/a
C	PB11/PB10	TIM2	UART3	I2C2
EXT-V	PC0	n/a	n/a	n/a
built-in ELRS	PC12/PD2	n/a	UART5	n/a

The pinout is extremely similar to the F7C reference design from Rotorflight. https://github.com/rotorflight/rotorflight-ref-design/blob/master/Reference-Design-F7C.md