ME405 Final Project - MECH13

Wiring Overview

This page defines the electrical interconnects used on our Romi robot, including motor driver control, encoder feedback, reflectance sensing, inertial sensing, and bump-event inputs. The goal is to provide a single reference for connector-level wiring, Nucleo pin assignments, and the signals required by each subsystem in the final autonomous robot.

STM32 Nucleo pinout reference used to assign PWM, analog, I2C, and digital I/O signals for the Romi wiring harness.

Red wire
Black wire
Yellow wire
Blue wire
Green wire
Orange wire
Brown wire
Gray wire
Purple wire
White wire

Nucleo Pin Constraints

Several Nucleo pins were avoided because they are tied to onboard functions such as ST-Link communication, USB, SWD programming, the user button, the onboard LED, and the RTC oscillator. Avoiding these pins helped preserve reliable programming, debugging, and serial access during development and testing.

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

Power

Signal	Connection	Wire Color	Notes
VIN	VIN	Red	Main battery power input
GND	GND	Black	Common ground reference for the system

Motor Control

The drivetrain used separate effort, direction, and enable lines for each motor. These connections supported closed-loop speed control and direction changes during line following, turning, and wall-response behaviors.

Motor	Signal	Nucleo Pin	Wire Color
Right	Motor Effort	PB6	Green
Right	Motor Direction	PA7	Blue
Right	Motor Enable	PA6	Yellow
Left	Motor Enable	PB3	Yellow
Left	Motor Direction	PB5	Blue
Left	Motor Effort	PB4	Green

Encoder Connections

Quadrature encoder feedback from both wheels was routed directly to the Nucleo so that the software could measure wheel speed and traveled distance for closed-loop motor control and state estimation.

Encoder	Signal	Nucleo Pin	Wire Color
Right	Encoder Channel B	PA1	Yellow
Right	Encoder Channel A	PA0	Blue
Left	Encoder Channel B	PA8	Blue
Left	Encoder Channel A	PA9	Yellow

IR Sensor Array

The line sensor array used seven analog reflectance channels. These signals were read by the controller to compute line position and steering error during centroid-based line following.

Sensor Channel	Nucleo Pin	Wire Color	Notes
Sensor 13	PC3	Brown	Outer channel
Sensor 11	PC2	Red	Outer-mid channel
Sensor 9	PC0	Orange	Mid channel
Sensor 7	PC1	Yellow	Center channel region
Sensor 5	PB0	Green	Center channel region
Sensor 3	PA4	Gray	Inner channel
Sensor 1	PC4	Purple	Outer channel
Sensor GND	GND	Black	Sensor ground
Sensor VCC	+3V3	White	Sensor supply voltage

IMU Connections

The BNO055 IMU was connected over I2C and powered from the 3.3 V rail. This interface provided heading information used during turning actions and observer-based state estimation.

IMU Signal	Nucleo Pin / Connection	Wire Color	Notes
SCL	PB9	Blue	I2C clock
SDA	PB8	Yellow	I2C data
Reset / Ground tie	GND	Green	Ground-related reset connection shown in the board table
GND	GND	Black	Ground reference
VIN	+3V3	Red	3.3 V supply from the controller

Bump Sensors

Left and right bumper switch assemblies were connected as grouped digital inputs. These signals were used by the navigation task to detect wall contact and trigger backing-up and recovery behaviors.

Side	Board Pin	Nucleo Pin	Wire Color
Right	BMP2	PB15	Yellow
Right	BMP1	PB14	Orange
Right	BMP0	PB13	Red
Left	BMP5	PC8	Yellow
Left	BMP4	PC6	Orange
Left	BMP3	PC5	Red

Wiring Diagram and Full Assembly

Final Romi wiring diagram — Final wiring diagram showing the pin-level interconnects used on the robot.

Fully assembled Romi robot — Fully assembled Romi with integrated controller stack, front sensors, and wiring harness used during obstacle-course testing.