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