DENKOBlue manual

Chapter 5 · Applies to firmware v408 and later · Updated 2026-09-21

Firmware updates and stock conversion

How the station's firmware is updated, how to install it by hand over USB, and how to convert the board to stock Blitzortung firmware and back. The Firmware page at /flash is the one page that can erase this firmware — read this chapter first.

This board is very hard to brick. Whatever you flash, recovery goes through the chip's own ROM loader, which is reachable whenever the board powers up at all — the normal state of these boards: BOOT0 is a physical button, and holding it while the board starts puts it in USB DFU mode, from which any working image can be written with a cable. A bad flash costs you a recovery procedure, never the board. The procedure is in section 3.

1. What the Firmware page shows

2. Automatic updates

Self-updating is off by default and is switched on by the fleet's remote configuration, not by anything on the board's pages. When it is on:

  1. The station checks a public update manifest about every 30 minutes. It only ever accepts a version newer than the one running, so the process is self-limiting.
  2. The download and installation are handed to the board's golden recovery image — the running firmware never erases itself. Keep the power on while this happens.
  3. The new image boots on trial and confirms itself. If it cannot, the bootloader gives it three boot attempts and then hands the board back to the recovery image. There is one application slot, so there is no previous image to return to: the recovery image keeps the network up, serves a plain-text status page at the station's address, leaves every indicator LED dark, and keeps checking the update manifest by itself: if a different release is published it installs that, otherwise it re-tries the copy it already has without downloading again. If the same release keeps failing the board stays in recovery until a new one is published. A bad update costs a few restarts, not the station — and a board in this state does not need USB recovery.

3. Installing by hand (USB DFU)

Use this for a board that has never run this firmware, or one whose flash no longer starts anything at all — not for a board that is sitting in the recovery image with the network up (section 2). You need a computer with a USB port and dfu-util. Download the current release and its checksum from fw.denko.asia. The image does not carry over any configuration, so the board will come up unconfigured.

Back up first. Before erasing a configured board, read its whole 1 MiB flash and keep the file — it is the only copy of what was there:
dfu-util -d 0483:df11 -a 0 -s 0x08000000:0x100000 -U before.bin

  1. Hold BOOT0, tap RESET, release BOOT0. The board enumerates as USB device 0483:df11. This works whenever the chip's own ROM loader is reachable, which is the normal state of these boards.
  2. Write the image: dfu-util -d 0483:df11 -a 0 -s 0x08000000 -D image.bin. An ST-LINK programmer (SWD) is the alternative when one is attached; write image.bin at 0x08000000.
  3. Read it back and compare. dfu-util -d 0483:df11 -a 0 -s 0x08000000:<bytes> -U after.bin, with the byte count shown on fw.denko.asia, then compare after.bin with image.bin. A write that verifies is a write you can trust; one that does not, repeat before powering the board into service.
  4. Tap RESET. The mode LED starts blinking, the board takes a DHCP address, and the web interface answers. The first boot runs as a bounded trial; once the Diagnostics page no longer shows it on trial, the install is confirmed. If that first-boot trial fails the board returns to its recovery image; repeat the write. Continue with the Quick start from the survey step.

4. Converting to stock Blitzortung firmware

The Firmware page can replace the DENKO Blue firmware with the official Blitzortung BLUE firmware. This is a deliberate, two-step operation — and it is worth being exact about what it costs before starting it:

The conversion erases flash sectors 0–7, including the station's stored configuration. The board comes back as the compiled fallback station number (8000) until it is configured again. Save anything you need from the Diagnostics page first — or better, keep a full flash backup (section 3).

While converted, the board is a live stock Blitzortung station. Do not leave it that way by accident.

  1. Get one of the exact official images: the published BLUE 9.4 or 10.1 file. Only those two files are accepted — the page checks the size (457,420 or 460,589 bytes) and verifies the image before it stages anything.
  2. Choose the file and press 1 — upload and stage. The board reboots into its golden recovery to receive the image, which can erase the tail of the running application. Stay on the page and finish — or retry — the upload; the page polls until recovery is ready and stages the file by itself.
  3. Press 2 — write it and reboot, and confirm. This replaces the bootloader and the remaining firmware. Do not power the board off. The page stops responding, because the board is now running stock firmware.
  4. Open the stock web interface (the board may take a new address) and configure it as a stock station.

5. The way back from stock

The return path is open, and it is open twice:

RouteNeedsWorks when
The official firmware's own update facilityNetwork access to the stationThat firmware is running and its web interface is up
USB DFU (section 3)Physical access: hold BOOT0, tap RESETWhenever the board's ROM loader is reachable — BOOT0 is a physical button, so this needs no working firmware

The way back runs in the other direction: from the official firmware, install the DENKO Blue image from fw.denko.asia with that firmware's own update facility. If that path is not available to you, USB DFU (section 3) needs no firmware at all.

If you flash an image that does not boot, neither web page is there to help: recovery then needs SWD or USB DFU. DFU works whenever the ROM loader is reachable (section 3) — that is the reassurance at the top of this chapter, and it is why the worst case is an afternoon, not a paperweight.