Architecture

Components

flowchart LR
    subgraph ESP["ESP32-C3"]
        ESPFW["ESP-Hosted firmware
Wi-Fi + BLE 5.0"]
    end

    subgraph F1C["Allwinner f1c200s"]
        direction TB
        subgraph LINUX["Linux 6.x rootfs (musl)"]
            SPDIF["sun4i-spdif"]
            ESPH["esp-hosted-ng"]
            GETHER["g_ether"]
        end
        UBOOT["U-Boot 2026.04"]
        SPL["U-Boot SPL"]
        UBOOT --> LINUX
        SPL --> UBOOT
    end

    NAND[("SPI NAND 128 MiB
boot / fota / rootfs / data")]

    ESPFW <-->|SPI + UART| ESPH
    NAND --> SPL
    SPDIF -->|SPDIF| SPDIFOUT([SPDIF out])
    GETHER -->|USB| USBC([USB-C host])

Sources of truth

Everything that ends up on the device is generated from this repository through Buildroot:

• buildroot_config/mds_<machine>_defconfig — Buildroot top-level config
• mds_external/ — BR2_EXTERNAL tree (boards, packages, defconfigs, overlays)
• mds_external/board/mds_network_player/ — board files used by the network player:
  • u-boot_defconfig, u-boot_devicetree.dts, uboot.env
  • kernel_defconfig, linux-patches/, uboot-patches/
  • image.its — FIT image description
  • mknandboot.sh, f1c100_uboot_spinand.sh — SPL/U-Boot relocation for SPI NAND boot
  • rootfs_overlay/, fota_rootfs_overlay/ — files added on top of the Buildroot rootfs
  • post-images.sh, post-images-fota.sh — post-build image assembly

Userspace highlights

• sun4i-spdif — kernel module driving the SPDIF output. The driver lives in mainline; see sound/soc/sunxi/sun4i-spdif.ko.
• g_ether — USB gadget that exposes the board to the host as an Ethernet device (default IP 192.168.2.2).
• esp-hosted-ng — host driver that runs over SPI to talk to the ESP32-C3 firmware. The repository vendors the ESP-Hosted sources under src/esp-hosted/.

Why musl

Buildroot is configured with the musl C library. This keeps the rootfs small and aligned with the ARMv5TE / 64 MiB constraints of the f1c200s.