Raspberry Pi Documentation

Raspberry Pi 4 specific documentation and resources.

Primary References

BCM2711 ARM Peripherals

BCM2711 ARM Peripherals PDF

Complete peripheral reference for the BCM2711 SoC used in Pi 4.

Key sections:

• Section 1.2: Address map and MMIO base (0xFE000000 for ARM access)
• Section 2: UART (PL011, mini UART)
  • 2.1: PL011 UART registers and configuration
• Section 5: GPIO
  • 5.2: Function select and pull-up/down configuration
• Section 6: Interrupts (GIC-400)
  • 6.1: GIC distributor base address (0xFF841000)
• Section 10: System Timer
  • 10.2: System timer registers at 0xFE003000

Important notes:

• Bus addresses in documentation (0x7E...) must be translated to ARM physical (0xFE...)
• Pi 4 MMIO base changed from Pi 3’s 0x3F000000 to 0xFE000000
• Clock frequencies differ from Pi 3 (e.g., PL011 UART: 54 MHz vs 48 MHz)

Pi 4 Schematics

Raspberry Pi 4 Reduced Schematics

Hardware schematics showing:

• Power supply routing
• GPIO pin connections
• UART pin assignments (GPIO 14/15 for TXD/RXD)
• Component placement

Device Tree Reference

Raspberry Pi Device Tree Documentation

Device tree overlays and parameters for:

• Enabling/disabling peripherals
• UART configuration
• GPIO function assignment

Useful for understanding hardware defaults and firmware configuration.

Boot Configuration

config.txt Settings

For bare-metal kernel deployment to SD card:

enable_uart=1        # Enable PL011 UART for serial console
arm_64bit=1          # Boot in AArch64 mode (required)
kernel=kernel8.img   # Kernel binary to load

Boot Process

1. GPU firmware (start4.elf) loads from SD card FAT partition
2. Firmware initializes hardware and reads config.txt
3. Firmware loads kernel8.img to 0x00080000
4. Firmware jumps to kernel entry point
5. Kernel runs in EL1 (supervisor mode)

See Boot Sequence for kernel-side boot flow.

Hardware Differences vs Pi 3

Code porting note: Always use memory-map constants, never hardcode Pi 3 addresses.

QEMU Emulation

raspi4b Machine Type

QEMU Raspberry Pi Documentation

• QEMU 9.0+ required for raspi4b machine type
• Emulates: CPU, RAM, UART, GPIO (partial), system timer
• Not emulated: PCI, Ethernet, WiFi, USB, GPU

QEMU vs Real Hardware

See ADR-002 for QEMU version requirements.

Useful Resources

• Raspberry Pi OS Documentation - Official docs
• BCM2711 Datasheet - Primary peripheral reference
• Device Tree Source - Kernel device trees (shows hardware configuration)

Related Documentation

• Memory Map - MMIO base addresses
• UART PL011 - UART hardware details
• ARM Documentation - ARM architecture references