DCLK
Dual-MIDI Clock
Firmware updates and settings over USB
How to flash
- Connect DCLK with a USB‑C data cable (plug it straight into the computer, not a hub). Stop any clock that is running and close apps using it as a MIDI device.
- Put it into DFU mode: click Enter update mode below, or choose UPDATE in DCLK's Settings menu. The screen shows DFU READY. Needs firmware 1.5 or later. On older firmware, or if DCLK won't start: hold BOOT0, tap NRST, keep holding BOOT0 for about one second, then let go. That can take two or three tries, and the OLED and LEDs stay off in that mode.
- Choose the firmware below, click Flash Firmware and pick STM32 BOOTLOADER in the popup.
- Wait for Done. DCLK restarts by itself. If it does not, press NRST once. Your saved settings (LED brightness, MIDI options) are kept: the flasher never erases the settings area.
Troubleshooting
STM32 BOOTLOADER is not in the list
The board is not in DFU mode yet. If your computer lists DCLK as a MIDI device instead, it is still running its normal firmware. Click Enter update mode again or use BOOT0 and NRST (step 2), try a different cable (many USB‑C cables are charge only) and plug directly into the computer. On Windows, Device Manager should show STM32 BOOTLOADER while it is in DFU mode.
Windows: "Access denied" or "Unable to claim interface"
Chrome can only talk to the bootloader through the WinUSB driver. Download Zadig, put the board in DFU mode, choose Options > List All Devices, select STM32 BOOTLOADER, pick WinUSB and click Replace Driver. This is needed once per computer.
Linux: the device appears but cannot be opened
Add a udev rule so your user can access it, for example SUBSYSTEM=="usb", ATTRS{idVendor}=="0483", ATTRS{idProduct}=="df11", MODE="0666" in /etc/udev/rules.d/50-stm32-dfu.rules, then unplug and replug the board.
Warnings about "A transfer error has occurred"
Some boards' built-in bootloader struggles with certain data patterns. The flasher works around this by itself: it skips blank data and resends any piece that fails in smaller parts, so a few warnings in the log are normal and the result is still checked byte by byte. If it gives up completely, try again or try another computer.
It flashed, but DCLK does not start
Make sure BOOT0 is released, then press NRST or unplug and replug. If you flashed a custom file, it must be built to start at 0x08000000 (no HID or UF2 bootloader offset); the flasher warns you when it is not. If it still does not start, click Download Log and send it to us.