STM32F767ZI to Raspberry Pi 5 UART Communication

1. Project Overview

This project demonstrates UART communication between an STM32F767ZI Nucleo-144 board and a Raspberry Pi 5.

• Problem being solved: Establishing a reliable UART link between STM32 and Pi for embedded system data exchange.
• Purpose: Allows the STM32 to send periodic status messages to the Raspberry Pi, forming the foundation for sensor or control data transfer.
• Demonstration: Counts incrementally transmitted from STM32 and displayed on the Raspberry Pi terminal.

2. System Architecture

• High-level description: STM32 runs a loop sending UART messages, Raspberry Pi receives them via GPIO UART pins.
• Data flow: STM32 → UART → Pi → Terminal Display
• Control flow: Simple polling loop on STM32, no interrupts used.

3. Hardware Design

• STM32F767ZI Nucleo-144: Chosen for high-performance Cortex-M7, multiple UARTs.
• Raspberry Pi 5: Receives UART data, acts as a display or processing unit.
• Jumper wires: For TX/RX and GND connections.

Power considerations: Both boards are powered by their standard USB sources.

4. Firmware / Software Design

• Firmware structure: HAL-based initialization, main loop sends messages.
• Tasks: Main polling loop, message formatting with counter.
• Code snippet:

int counter = 0;
char msg[50];
while(1) {
    sprintf(msg, "Hello STM32! Count=%d\r\n", counter++);
    HAL_UART_Transmit(&huart3, (uint8_t*)msg, strlen(msg), HAL_MAX_DELAY);
    HAL_Delay(1000);
}

• Timing: 1-second interval between messages.

5. Communication & Interfaces

• Protocol: UART (USART3)
• Reason: Simple, low-latency point-to-point communication.

6. Implementation Highlights

• Correct GPIO alternate function configuration for PB10/PB11.
• Use of HAL_UART_Transmit in blocking mode for simplicity.
• Counter-based message to verify continuous communication.
• Minimal code footprint for embedded teaching or prototyping.

7. Challenges & Debugging

• Initial blank screen on Pi due to serial-getty and default UART mapping.
• Resolved by disabling serial console, enabling hardware UART, and verifying pinctrl mapping.
• Python loopback test used to verify Pi UART before connecting STM32.

8. Results & Demonstration

• STM32 transmits "Hello STM32! Count=N" every second.
• Raspberry Pi terminal (screen /dev/serial0 115200) receives messages in real-time.
• Validates end-to-end UART communication.

9. Security, Reliability, or Safety Notes

• Pull-up resistors configured on PB10/PB11 for stable logic levels.
• UART blocking transmit ensures no message loss in this simple demo.
• Grounding required between STM32 and Pi.

10. Future Improvements

• Implement STM32 RX handling to allow bidirectional communication.
• Add message framing and checksums for robust data transfer.
• Integrate into a larger sensor or control system.
• Explore DMA-based UART for non-blocking transmissions.

11. Repository Structure

/core        -> Core STM32 firmware code
/driver      -> Peripheral drivers
/images      -> Diagrams, pinout, screenshots
/README.md   -> Project documentation
/LICENSE     -> License file (stay intact)

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Platform-Specific Notes (STM32)

• MCU: STM32F767ZI Cortex-M7
• HAL Drivers: Used for UART, GPIO, and system clock
• Debugging tools: ST-Link, CubeIDE
• UART AF: PB10 (TX), PB11 (RX), AF7
• No RTOS: Bare-metal polling loop for simplicity
• Clock: HSI + PLL configuration for system stability