Let's boot Apache NuttX RTOS on PineVox!

• BL606P is the newer, scaled-down variant of BL808 (minus the Low-Power Core)
• NuttX already supports Ox64 BL808
• So NuttX might boot on PineVox BL606P!

BL606P looks something like this (minus the Low-Power Core)...

What's inside PineVox?

According to the PineVox Schematic...

• Mainboard PCB contains Bouffalo Lab BL606P SoC, Serial Console, Flash Memory, USB-C Port, Power Mgmt

• Sideboard PCB contains Directional Microphone, Buttons, LEDs

• Connected by a 20-pin Ribbon Cable

USB-C Port connects to a Special USB Cable for PineVox that exposes (pic below)...

• Boot Switch (GPIO 29)

  1: Boot from UART (Flashing Mode?)

  0: Boot from Flash

• UART TX / RX (GPIO 20 / 21)

  (We assume it's for Flashing via BLDevCube)

• USB Data (+ve and -ve)

  (For USB Peripherals? Maybe DFU?)

(Schematics will be published soon by PINE64)

How to flash PineVox with OpenSBI and U-Boot Bootloader?

Let's try flashing PineVox with BLDevCube...

• m0_lowload for M0 Wireless Core (32-bit):

  Firmware that forwards Peripheral Interrupts to the D0 Multimedia Core.

  (Like SD Card and GPIO Interrupts)

• d0_lowload for D0 Multimedia Core (64-bit):

  Basic Bootloader that loads OpenSBI, U-Boot Bootloader and Device Tree into RAM.

• As explained here: "Flash OpenSBI and U-Boot"

TODO: Flash OpenSBI and U-Boot Bootloader

How to boot NuttX on PineVox?

We have a problem...

• NuttX boots on Ox64 via microSD. But PineVox doesn't have a microSD Port! (Though BL606P supports microSD)

• Ox64 supports booting over Ethernet (with U-Boot Bootloader). But BL606P doesn't support Ethernet!

• We need a way to load NuttX Image into RAM at 0x5020_0000

• Maybe the M0 Wireless Core (32-bit) will load NuttX Image into RAM? Over WiFi?

Why use U-Boot Bootloader? Why not flash NuttX directly as Firmware?

• U-Boot might be simpler for now? Today NuttX boots in RISC-V Supervisor Mode, so we don't need to tweak it to boot in Machine Mode.

• Isolate the Toolchain: BL606P needs a special T-Head C906 Toolchain plus Bouffalo Lab SDK. It's better to isolate OpenSBI + U-Boot, compile them with the special toolchain.

  We'll keep them separate from NuttX, which compiles with the popular GCC Toolchain.

• Support Direct Firmware Update (DFU): In future we might support DFU to upgrade the NuttX Image wirelessly. We'll implement DFU with U-Boot (or something similar).

TODO: Load NuttX Image into RAM