---
title: Architecture Overview of the BDYG18Pro Armbian Build System
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created_at: '2026-08-08T10:02:33.012303+00:00'
updated_at: '2026-08-16T18:45:05.147636+00:00'
tags:
- hardware
- boot
- docker
- repo
---

# Architecture Overview

## 1. Hardware Platform

| Component | Specification |
|-----------|---------------|
| **SoC** | Rockchip RK3568 – quad‑core Cortex‑A55 @ 2 GHz, Mali‑G710 GPU, VPU, RGA, HDMI, PCIe, USB 3.0. |
| **Memory** | 8 GB DDR4 HS200 (2.5 V). |
| **Storage** | 256 GB eMMC (boot + rootfs) + 32 MB Winbond W25Q256JW SPI‑NOR (blank). |
| **Switch** | Realtek RTL8367S 5‑port DSA (GMAC1 active, GMAC0 disabled). |
| **Network** | Ethernet MAC‑1 (`end0`), TSO disabled, TCP congestion = **Cubic**. |
| **UART console** | `serial@fe660000` → `ttyS2` @ 1 500 000 baud (pins RX/D0, TX/D1). |

*Source*: `evidence/dtb/rk3568-bdy-g18-pro.fixed.dts`, `evidence/dtb/rk3568-bdy-g18-pro.orig.dts`.

## 2. Boot Flow

1. **MaskROM** reads SPL from DDR (address 0x08000) after power‑on.  
2. **SPL** (Rockchip `rk356x_spl_loader_v1.25.114.bin` preferred) initialises DDR and loads **U‑Boot** (mainline 2026.04) from the SPL payload.  
3. **U‑Boot** loads a **FIT** image (`uboot‑fit‑rk3568‑bdy‑g18‑pro.dts`) containing BL31, kernel, and DTB.  
4. Kernel `Linux 6.18.40‑current‑rockchip64` boots with DTB `rk3568‑bdy‑g18‑pro.dtb`.

All steps are verified by flashing the SPL to SPI‑NOR, reading back SHA‑256, and confirming boot success (see `evidence/selfbuilt-uboot-brideup.txt`).

## 3. Repository Layout & Build Infrastructure

| Directory | Purpose |
|-----------|---------|
| `arm64‑custom/` | Custom board scripts & patches (tracked). |
| `evidence/` | Raw logs, screenshots, serial captures (tracked). |
| `aidocs/` | Additional documentation (tracked). |
| `outputs/armbian-g18pro/` | Final artefacts – compressed image, SHA‑256 manifest, verification report. |
| `armbian‑g18pro‑cache` (Docker volume) | Persistent cache (~19 GB) for U‑Boot, kernel, ccache. |

*Build orchestrator*: Python script `armbian‑custom/build_g18pro.py` + PowerShell wrapper `build_g18pro.ps1`. Docker image `ghcr.io/armbian/docker-armbian-build:armbian-ubuntu-noble-latest` is used; shallow Git clones (`--depth 1`) minimise download size.

## 4. Runtime System State (as of 16 Aug 2026)

- **Kernel**: `6.18.40‑current‑rockchip64`
- **U‑Boot**: Mainline v2026.04 on SPI‑NOR; vendor U‑Boot remains on eMMC as fallback.
- **Network**: `tso` off, `cubic` congestion, throughput ≈ 30 Mbps.
- **Power‑off**: `systemctl poweroff` hangs (requires manual power‑cycle); `syscon‑reboot‑mode` DTB node restores clean reboot.
- **Docker cache**: volume present, speeds up incremental builds.

*Source*: `abe4221f-b290-4384-ad8f-1f72c360b893`.

---

**References**

- `c650c1e4-18ee-44ad-af42-b7632fbdcf5c`
- `dd496c6d-1619-457d-86a9-da57f5b866d7`
- `S-1`
- `aa3057ab-54c5-4ffc-ba85-c2f2396ee60c`
- `bf88c265-4749-4c50-85bc-4bae25298cd5`
- `ff34c6eb-6bba-41e5-9e43-ff80941fa823`
- `adb3722a-51e7-4ec5-88cc-a95dc399a7a1`
- `abe4221f-b290-4384-ad8f-1f72c360b893`