Open-source bootloader for the Centauri Carbon mainboard / Allwinner R528 SoC

This repository contains an open-source bootloader for the Centauri Carbon mainboard, which uses the Allwinner R528 SoC.

Prerequisites

Before you begin, ensure you have the following prerequisites installed and configured:

• GCC ARM Toolchain: You'll need the gcc-arm-none-eabi package to cross-compile for the ARM architecture.
• sunxi-tools: This collection of tools is essential for working with Allwinner SoCs. It includes sunxi-fel, which is used to communicate with the device in FEL mode.
• Serial Interface: A serial interface connected to UART0 on the Centauri Carbon mainboard is required for debugging and communication.
• FEL USB Connection: You'll need to connect your computer to the USB-C hotend port on the mainboard. EXTREME CAUTION: Ensure that the 24V VCC is NOT mated, as this can be dangerous.

On a Debian or Ubuntu-based system, you can install the required packages with the following command:

sudo apt install gcc-arm-none-eabi sunxi-tools

Getting Started

1. Build: To build the hello world example and the cc-boot bootloader, run the following command:

   make

2. Flash "Hello World": To flash the hello world example to the device, use the following command. This will use sunxi-fel to flash the application.

   make flash-hello

3. Flash Bootloader: To flash the bootloader, use the following command. Please note that the bootloader is currently under development and does not yet have full bootloader functionality.

   make flash-boot

Note: Both hello and boot leverage UART0 on the CC mainboard. When you flash using make or manually using sunxi-fel, have a 3.3v serial adaptor plugged into UART0 and a terminal connected at 115200 to see the output from either program.

Resources

• FEL - linux-sunxi.org: An excellent resource for understanding the FEL mode on Allwinner devices. FEL is a low-level subroutine in the BootROM used for initial programming and recovery via USB.
• linux-sunxi/sunxi-tools: The official repository for the sunxi-tools command-line utilities.
• awboot: A related bootloader project that has served as a reference.
• U-Boot Patch for Allwinner R528: A U-Boot mailing list thread discussing the addition of DRAM initialization for the R528 SoC, which is relevant to this project.
• 100ask-t113-pro eLinuxCore SDK: The T113 Pro SDK, which is for a very similar and binary-compatible Allwinner chipset to the R528. This is a valuable reference for hardware and bootloader specifics.

License

This project is licensed under the GNU General Public License v2.0. See the LICENSE.md file for more details.