STM32 Robot Board Pin Mapping Strategy — Migrating from Teensy

Robot Board Pin Mapping Strategy

Pin mapping comparison between Teensy 4.1 and STM32H743

7.1 Pin Assignment Principles

1. Prevent AF conflicts: Only one AF can be used per pin
2. Secure power/ground connections: All 18 power pins on LQFP-100 must be properly connected
3. Noise isolation: ADC input pins must be physically separated from high-speed digital signals (CAN, SPI)
4. Protect debugger pins: PA13 (SWDIO) and PA14 (SWCLK) must never be repurposed
5. Handle unused pins: Set to Analog mode (minimizes current draw) or Output Low
6. BOOT0 pin: Connect to GND (normal boot = execute from Flash)

7.2 Teensy → STM32 Pin Mapping Table

Final mapping table from the current Board.h Teensy 4.1 pin configuration to STM32H743VITx:

Communication Peripherals

Function	Teensy Pin	STM32 Pin	AF	Peripheral	Notes
CAN TX	22	PD1	AF9	FDCAN1_TX	Motor CAN bus
CAN RX	23	PD0	AF9	FDCAN1_RX	Motor CAN bus
IMU UART RX	16 (RX4)	PD9	AF7	USART3_RX	IMU data receive
IMU UART TX	N/C	PD8	AF7	USART3_TX	(can double as debug)
SPI SCK	(implicit)	PA5	AF5	SPI1_SCK	Coms MCU communication
SPI MOSI	11	PB5	AF5	SPI1_MOSI	PA7 reserved for ADC
SPI MISO	(implicit)	PB4	AF5	SPI1_MISO	PA6 reserved for ADC
SPI CS	10	PA15	GPIO	—	Software CS
SPI IRQ	34	PE0	GPIO	EXTI0	Interrupt input
SPI RST	4	PE1	GPIO	—	Coms MCU reset
Serial TX	1	PA9	AF7	USART1_TX	(debug/PC communication)
Serial RX	0	PA10	AF7	USART1_RX	(debug/PC communication)

Analog Inputs (ADC)

Function	Teensy Pin	STM32 Pin	Channel	Peripheral	Notes
Torque Sensor Left	A16	PA0	IN0	ADC1	Load cell L
Torque Sensor Right	A6	PA3	IN3	ADC1	Load cell R (PA3 instead of PA6)
Angle Sensor Left	A13	PC3	IN13	ADC1	Left ankle angle
Angle Sensor Right	A12	PC2	IN12	ADC1	Right ankle angle
Maxon Current Left	(maxon_current)	PA1	IN1	ADC1	Left motor current
Maxon Current Right	(maxon_current)	PA2	IN2	ADC1	Right motor current
(Spare 1)	—	PC4	IN14	ADC1	For expansion
(Spare 2)	—	PC5	IN15	ADC1	For expansion

PWM Outputs

Function	Teensy Pin	STM32 Pin	AF	Peripheral	Notes
Maxon PWM Left	(maxon_ctrl_L)	PE9	AF1	TIM1_CH1	Left motor
Maxon PWM Right	(maxon_ctrl_R)	PE11	AF1	TIM1_CH2	Right motor

GPIO Outputs

Function	Teensy Pin	STM32 Pin	Configuration	Notes
Status LED Red	14	PB0	Output PP, Low Speed	RGB LED
Status LED Green	25	PB1	Output PP, Low Speed	RGB LED
Status LED Blue	24	PB2	Output PP, Low Speed	RGB LED
Sync LED	15	PB10	Output PP, Low Speed	Sync LED
Motor Stop	9	PC6	Output PP, Pull-Down	Emergency stop
Motor Enable L0	28	PD3	Output PP, Pull-Down	Left joint 0
Motor Enable L1	29	PD4	Output PP, Pull-Down	Left joint 1
Motor Enable R0	8	PD5	Output PP, Pull-Down	Right joint 0
Motor Enable R1	7	PD6	Output PP, Pull-Down	Right joint 1
Sync Default	5	PC7	Output PP	Sync default
Speed Check	33	PC8	Output PP	Toggle pin for timing measurement

GPIO Inputs

Function	Teensy Pin	STM32 Pin	Configuration	Notes
Maxon Error Left	(maxon_err_L)	PE2	Input, Pull-Up	Error detection (active low)
Maxon Error Right	(maxon_err_R)	PE3	Input, Pull-Up	Error detection (active low)

System Pins (Do Not Change)

Function	STM32 Pin	Notes
SWDIO (Debugger)	PA13	Never reassign
SWCLK (Debugger)	PA14	Never reassign
HSE Crystal IN	PH0 (pin 12)	8MHz crystal
HSE Crystal OUT	PH1 (pin 13)	8MHz crystal
NRST	pin 14 (NRST)	Reset button
BOOT0	pin 94	Connected to GND (Flash boot)

7.3 AF Conflict Verification

Key conflict resolutions in the above mapping:

Issue	Cause	Resolution
PA6 cannot be used for both ADC and SPI1_MISO	AF conflict	Move SPI1_MISO to PB4 (AF5)
PA7 cannot be used for both ADC and SPI1_MOSI	AF conflict	Move SPI1_MOSI to PB5 (AF5)
PA1 cannot be used for both ADC (current sensing) and UART4_RX	AF conflict	Move IMU UART to USART3 (PD8/PD9)
PA6 used for torque sensor R ADC conflicts with SPI	AF conflict	Move torque sensor R to PA3 (ADC1_IN3)

7.4 Pin Usage Summary

Port	Used Pins	Unused Pins	Notes
GPIOA	PA0-5, PA9-10, PA13-15	PA6-8, PA11-12	PA11/12 reserved for USB
GPIOB	PB0-2, PB4-5, PB10	PB3, PB6-9, PB11-15	Plenty of room
GPIOC	PC2-8	PC0-1, PC9-13	PC13 can be WKUP
GPIOD	PD0-1, PD3-6, PD8-9	PD2, PD7, PD10-15	Plenty of room
GPIOE	PE0-3, PE9, PE11	PE4-8, PE10, PE12-15	Plenty of room

Total pins used: ~40 / Spare pins: ~36 — plenty of room for future expansion

7.5 Pin Map Documentation

The finalized pin mapping should be written to Documentation/Hardware/AR_Walker_STM32_Pinmap.md using the templates/hardware_pinmap_template.md template.

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