BatMetal

Bare Metal Kernel for Raspberry Pi 5 Sonar Mapping

BatMetal is a lightweight, Rust-based bare metal kernel designed for the Raspberry Pi 5. Its primary mission is to provide a real-time, low-latency platform for ultrasonic sonar mapping operations, bypassing the overhead of a traditional operating system.

Currently, it serves as a robust hardware abstraction layer verifying RP1 (Southbridge) access, UART communication, and GPIO control.

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Hardware Configuration

Pinout & GPIOs

GPIO Pin	Function	Description
GPIO 14	UART0 TX	Serial Console Transmit (Connected to Adapter RX)
GPIO 15	UART0 RX	Serial Console Receive (Connected to Adapter TX)
GPIO 18	SERVO PWM	9g Servo Motor Control (50Hz Software PWM)
GPIO 6	ALIVE_LED	Alive Status Indicator (Blinks during normal operation)
GPIO 5	ERROR_LED	Panic/Error Indicator (Blinked by Panic Handler)
ACT LED	Onboard	Activity LED (Green) - Used for Boot/Panic status

Memory Map (Crucial for Pi 5)

The Raspberry Pi 5 uses a split architecture with the RP1 I/O Controller connected via PCIe.

• RP1 Base Address (CPU View): 0x1f00000000 (BAR0)
• UART0 Offset: 0x30000
• Note: The Firmware initializes UART0 at 0x1c..., but the Kernel must access it via the PCIe BAR0 mapping at 0x1f....

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Getting Started

Prerequisites

• Rust Toolchain (Nightly recommended for no_std)
• Cross-Compiler Tools: aarch64-linux-gnu-binutils (for objcopy)
• Hardware: Raspberry Pi 5, USB-to-UART Adapter (3.3V logic)

Build Instructions

1. Install Target:

   rustup target add aarch64-unknown-none

2. Compile & Link:

   make

   This produces kernel8.img.

3. Flash:

   • Format an SD card with FAT32.
   • Copy standard Pi 5 boot files (bcm2712-rpi-5-b.dtb, config.txt, etc.).
   • Copy kernel8.img to the root.
   • Ensure config.txt contains:

     os_prefix=
     check_syslin_rom=0
     enable_uart=1

4. Run: Connect UART adapter and power on.

   sudo minicom -D /dev/ttyUSB0 -b 115200

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Roadmap: Project "Sonar"

The ultimate goal of BatMetal is Autonomous Sonar Mapping. Future implementations will include:

• HC-SR04 Driver: Precise microsecond timing for ultrasonic triggering and echo measurement.
• Servo Control: PWM generation to sweep the sonar sensor (Radar style).
• Point Cloud Storage: In-memory mapping of detected obstacles.
• Visualization: Exporting polar coordinate data via UART for external rendering.

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🛠 Tech Stack

• Language: Rust 🦀
• Architecture: AArch64 (ARM64)
• Platform: Raspberry Pi 5 (BCM2712 + RP1)
• Approach: Bare Metal (No OS)

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"In the silence of bare metal, every echo counts."