Wiring

This page defines the electrical interconnects used on Romi, including motor driver control, encoder feedback, reflectance sensing, inertial sensing, bump event inputs, battery monitoring, and Bluetooth serial communication. The goal is to provide a single reference for connector level wiring, Nucleo pin assignments, and the signals required by each subsystem task.

STM32 Nucleo pinout reference used to assign timer, ADC, I2C, and UART signals for the Romi wiring harness.

Nucleo Pin Constraints

Several STM32 Nucleo pins are reserved for onboard functions such as ST-Link communication, USB, SWD programming, the user LED and button, and the 32 kHz oscillator. These pins were treated as unavailable during integration to preserve reliable REPL access, firmware flashing, and debugging support throughout development and testing.

Reserved Nucleo pins that were avoided to prevent conflicts with ST-Link, USB, SWD, onboard LED and button, and RTC oscillator functions.

Reserved pins not used in this project

Nucleo Pin	Arduino Label	Reserved Function
PA2	A2	UART2 link to ST-Link interface
PA3	A3	UART2 link to ST-Link interface
PA5	A5	Onboard user LED
PA11	A11	USB interface signals through the shoe
PA12	A12	USB interface signals through the shoe
PA13	A13	SWD programming interface
PA14	A14	SWD programming interface
PC13	C13	User button input
PC14	C14	32 kHz oscillator for RTC
PC15	C15	32 kHz oscillator for RTC

Motor Control

Motor driver pin mapping

Motor	Signal	NUCLEO Pin	Timer / Channel
Left	Enable	PB0	Digital output
Left	PWM A	PC12	TIM3 CH3
Left	PWM B	PC10	TIM3 CH3
Right	Enable	PC9	Digital output
Right	PWM A	PH1	TIM3 CH4
Right	PWM B	PH0	TIM3 CH4

Motor control wiring using TIM3 PWM channels for effort commands and dedicated enable lines for each motor driver.

Encoder Connections

Quadrature encoder mapping

Encoder	Signal	NUCLEO Pin	Timer / Channel
Left	Channel A	PA0	TIM2 CH1
Left	Channel B	PB3	TIM2 CH2
Right	Channel A	PA8	TIM1 CH1
Right	Channel B	PA9	TIM1 CH2

Encoder wiring using hardware timer encoder mode to produce wheel position and velocity feedback for control, odometry, and navigation.

Battery Monitoring

Battery ADC input

Signal	NUCLEO Pin	Notes
Battery ADC	PC0	ADC input from voltage divider output

Battery voltage measurement routed to an ADC channel for runtime monitoring and diagnostics.

IR Sensor Array

Reflectance sensor channel mapping

Channel	NUCLEO Pin	Position
1	PC4	Left far
2	PB1	Left mid
3	PA7	Left near
4	PC1	Center
5	PA4	Right near
6	PA1	Right mid
7	PC3	Right far

Seven channel reflectance array wiring used for centroid based line error computation in the line following controller.

IMU Connections

BNO055 I2C and reset mapping

BNO055 Pin	Wire Color	NUCLEO Pin	Notes
SDA	Purple	B14	I2C data
SCL	Grey	B13	I2C clock
RST	White	B15	Hardware reset line

BNO055 wiring over I2C with a dedicated reset pin to support deterministic startup and calibration handling.

Bump Sensors

Bump sensor wiring and jumpers

Side	Board Pin	Wire Color	NUCLEO Pin
Right	BMP 0	Purple	C11
Right	BMP 1	-	Jumper to 0
Right	BMP 2	-	Jumper to 0
Left	BMP 3	Teal	Jumper to 2
Left	BMP 4	-	Jumper to 3
Left	BMP 5	-	Jumper to 3

Bump sensor wiring consolidated into a single event input used by navigation for collision detection and recovery sequencing.

Bluetooth Serial

UART1 Bluetooth pin mapping

Signal	NUCLEO Pin	Notes
TX	B6	UART1 transmit to Bluetooth RX
RX	B7	UART1 receive from Bluetooth TX

Bluetooth serial link on UART1 used for calibration commands, trial parameters, and runtime telemetry at 460800 baud.

Full Assembly

Fully assembled Romi with integrated wiring harness, controller stack, and sensor mounts configured for obstacle course trials.