Installing Firmware¶

Note

Pando is a split keyboard with an MCU on the master half only. The secondary half uses an I/O expander over I2C, so only the master MCU needs to be flashed.

There are two ways to get the latest Vial firmware for Pando:

Precompiled firmware — Download precompiled firmware from GitHub Releases and flash via dfu-util (simplest option).
Manual build method — Clone the vial-qmk repo, build locally, and flash via CLI.

Prerequisites: Enable the Boot Button (Legacy Boot Mode)¶

Note

This step is not required for pre-built keyboards from my Etsy Store as it has already been completed.

The STM32G0 series handles booting differently from older STM32 parts. Booting is controlled by a software configuration bit called nBOOT_SEL in the Option Bytes rather than purely by hardware.

By default, nBOOT_SEL is set to 1, which tells the MCU to ignore the physical BOOT0 pin entirely. Instead it uses an Empty Check mechanism: a blank chip automatically enters DFU mode, but once code is flashed, it always boots straight into your firmware — ignoring BOOT0 even if it's held HIGH.

Why?¶

The BOOT0 pin on the G0 is multiplexed with GPIOs and programming lines (e.g. SWCLK on PA14). Disabling it by default lets designers use that pin as a regular I/O without risking accidental bootloader entry.

Enabling Legacy Boot Behavior¶

To restore hardware BOOT0 control (so a physical button can force DFU mode at any time), clear the nBOOT_SEL bit. This can be done via the GUI or the CLI, both using the STM32CubeProgrammer tool.

GUI method: Open STM32CubeProgrammer → Option Bytes → User Configuration, uncheck nBOOT_SEL, and apply.

CLI method: Use STM32_Programmer_CLI to list devices, display option bytes, and set the bit.

First, list available DFU devices:

$ STM32_Programmer_CLI -l

=====  DFU Interface   =====

Total number of available STM32 device in DFU mode: 1

  Device Index           : USB1
  Product ID             : DFU in FS Mode
  Device ID              : 0x0467

Display current option bytes (factory default shows nBOOT_SEL : 0x1):

$ STM32_Programmer_CLI -c port=usb1 -ob displ

  User Configuration:

     nBOOT_SEL    : 0x1 (BOOT0 signal is defined by nBOOT0 option bit)

Clear nBOOT_SEL to enable legacy boot pin behavior:

$ STM32_Programmer_CLI -c port=usb1 -ob nBOOT_SEL=0

OPTION BYTE PROGRAMMING VERIFICATION:

Option Bytes successfully programmed

Confirm the change (nBOOT_SEL now shows 0x0):

$ STM32_Programmer_CLI -c port=usb1 -ob displ

  User Configuration:

     nBOOT_SEL    : 0x0 (BOOT0 signal is defined by BOOT0 pin value (legacy mode))

Recommended Setup Sequence¶

Clear the option byte on a fresh chip before flashing firmware. This ensures the BOOT0 pin is active even if your first firmware build has a catastrophic bug, guaranteeing you can always recover via DFU:

Brand New MCU → Clear nBOOT_SEL → Test Bootloader → Flash Firmware

Precompiled Method: Download from Releases + `dfu-util`¶

Go to the Releases page
Download the latest firmware file (e.g. jyap808_pando_vial.bin)
Put the keyboard into DFU mode by holding the boot/reset button on the MCU while plugging in the USBC cable.
Flash the firmware with dfu-util:
```
dfu-util -d 0483:df11 -a 0 -s 0x08000000:leave -D jyap808_pando_vial.bin
```
The device should show up as an STM32 BOOTLOADER. On Linux you may need sudo or a udev rule for the DFU device.

A quick breakdown of the dfu-util flags:
- -d 0483:df11 — the USB VID:PID of ST's STM32 bootloader, which all STM32-system-DFU devices enumerate as.
- -a 0 — select alternate 0, the internal flash media. This is the same alternate QMK uses when flashing stm32-dfu boards.
- -s 0x08000000:leave — program at 0x08000000, the standard STM32G0 flash base address, then leave to jump to the application on completion.
The keyboard will reboot with the new firmware

Manual Build Method: CLI Build + Flash (Advanced)¶

Clone the official Vial QMK fork:

git clone https://github.com/vial-kb/vial-qmk.git
cd vial-qmk

Initialize submodules (important for QMK dependencies):
```
make git-submodule
```
Clone or download the Pando keyboard folder from the GitHub repo.

Copy the entire firmware/keyboards/jyap808/pando/ folder into vial-qmk/keyboards/jyap808/pando/.
Compile the Vial firmware:
```
make jyap808/pando:vial
```
Flash using the CLI.

For an STM32 target this uses USB DFU. You can use QMK's wrapper, which runs dfu-util under the hood:
```
qmk flash jyap808/pando:vial
```