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One-time USB flash

SQMeter v0.3 moves to a new partition layout that uses the whole 4 MB flash: two 1.75 MB firmware slots instead of 1.5 MB, so there's room for new features. A partition layout can only be changed over USB, so each device needs one USB flash to get onto v0.3. After that it updates over WiFi again, as before.

Your settings are kept, WiFi included. They live in a part of the flash this doesn't write.

You need a computer with Chrome or Edge (for the browser flasher) or Python (for esptool), and a USB data cable.

Browser flasher

  1. Plug the ESP32 into the computer.
  2. Click the button for your build: the one your device runs now (System page → Firmware) if you're moving an existing device.
  3. Pick the device's serial port, then Install.
  4. Leave "Erase device" unticked, then confirm. Ticking it wipes your settings.
  5. Wait for "Installation complete" (about a minute), then unplug and power the device as usual.

No port to pick?

The ESP32 needs a USB-to-serial driver on some computers (CP210x or CH340, depending on the board), and some USB cables only carry power.

esptool

Download the USB package for your build from the release: sqmeter-l2-usb-standard-*.zip or sqmeter-l2-usb-ble-*.zip. Unzip it, and from that folder:

pip install esptool
esptool.py --chip esp32 --port PORT --baud 460800 write_flash \
  0x1000 bootloader.bin 0x8000 partitions.bin 0xE000 boot_app0.bin \
  0x10000 firmware.bin 0x390000 littlefs.bin

Don't add --erase-all and don't run erase_flash: both wipe your settings. See Flashing for finding the port.

Check it worked

Open the device's page as before (its address and sqmeter.local don't change):

  • System → Firmware shows v0.3 or later.
  • Your settings are as you left them.
  • http://sqmeter.local/api/status shows "layout": "l2" under firmware.

If the device comes up as the SQM-Setup hotspot instead, its settings didn't survive (for example "Erase device" was ticked): join the hotspot and set it up again (First Boot).

Why it's needed

Before (v0.2) After (v0.3)
Firmware slots 1.5 MB (standard) or 1.69 MB (Bluetooth) each 1.75 MB each, both builds
Web UI (LittleFS) 512 KB 448 KB (the web UI is now stored compressed, about 150 KB)
Free flash up to 448 KB unused none

v0.3 is also built on a newer platform (Arduino-ESP32 3.x / ESP-IDF 5.5), with IPv6 for secure connections and time sync. The bigger slots are what let it fit with room to grow.

Over-the-air updates can't change a partition table, and v0.3's files are built for the new layout, so a device on v0.2 isn't offered v0.3 by its Updates page. If you upload a v0.3 file to a v0.2 device by hand, it won't fit and the update fails without changing anything.

Going back to v0.2

Flash v0.2.0-beta.3's sqmeter-complete-flash-*.bin (or sqmeter-ble-complete-flash-*.bin) at 0x0 as its release describes. That image includes the old layout and resets the settings: set the device up again from its hotspot.