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esphome-xiaomi_bslamp2/doc/flashing.md

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< Configuration guide | Index | Known issues >

Flashing guide

Tools needed

  • Allen key (2mm, 5/64") or torx (T8) screw driver
  • Soldering Iron
  • A serial to USB adapter (FTDI)
  • Some wires
  • Optional: sticky tape, hot glue

Warning

We have writen these instructions with care, but we will give absolutely no warranty. Perhaps you will destroy your lamp and your computer.

Opening the lamp, to expose the PCB

Remove the rubber pads from the botton of the lamp, to get access to 4 screws that attach the bottom to the rest of the lamp.

Note that you don't have to remove these pads fully. Once you can access the screws, you've gone far enough.

Unbolt the 4 screws which were hidden under the rubber pads.

Detach the bottom from the rest of the lamp, exposing the PCB. This might take a bit of force. Just pull it off bit by bit, until it pops loose.

Solder the wires

The wires will be connected to the debug pads that are shown in the following image.

Many of the serial to USB adapter have some header pins to which you can connect the wires of a device. Therefore, it might be useful to take some dupont wires, cut off one end, and solder the stripped end to the board.

Note: Whether to use male or female dupont wires depends on how you want to connect the serial adapter. In this example, I have used male wires, so I could plug them into a breadbord.

Solder the wires to the RX, TX, GND and GPIO0 debug pads.

Note: The board has a debug pad that exposes 3.3V. It is not required to solder a wire to this debug pad. For that reason, I have not marked this debug pad in the images. This pad is not directly connected to the 3.3V Vin of the ESP32 chip, making it a less than optimal candidate for powering the board during flashing. Instead, powering the lamp using its own power supply works best.

You could use some sticky tape to fixate the cables before soldering.

When you want to keep the wires attached after flashing the new firmware, then you might want to apply some hot glue to fixate the wires. This prevents the wires from breaking off, due to excessive movement.

Connect the wires to your serial to USB adapter

The wires must be connected as follows:

Soldering point Serial USB Adapter name
GND GND
TX RX
RX TX
GPIO0 GND

To be able to flash the lamp, GPIO0 must be connected to ground while the lamp boots up. Therefore, connect these wires before plugging in the lamp's power supply. Flashing will not work if you connect these wires after the lamp has already been booted up.

When you only have one GND pin on your USB Adapter

If your USB Adapter does not have multiple GND pins, then you'll have to find another way to attach GPIO0 to ground. Some options:

  • Use a breadbord, so you can connect the USB Adapter GND pin to a row on the bread bord, and connect the GND and GPIO0 wires of the lamp's board to that same row.

  • Solder a button on the board that connects GPIO0 to GND when pressed. Then you can hold down this button while plugging in the lamp's power supply. After booting up, you can release the button (the serial console will also mention that flash mode is now enabled). This is not the most practical solution for most people (since only one such flash operation is needed, from then on OTA - Over The Air - updates are possible), but it was a great help to me during the initial reverse engineering and firmware development.

  • Manually hold a wire connected to both a GND surface (e.g. the silver pad on the left of the board) and the GPIO0 debug pad, while plugging in the power supply. After booting, the wire can be removed. This is very fiddly way of doing it (a third hand would be very welcome with this), but it can be done.

  • You could opt for temporarily soldering a lead between GND and GPIO0 on the board, making GPIO0 pulled to ground permanently. It is a bit less flexible than some other options, but if you only need to do the initial backup and firmware flash of the lamp, then this can be all that you need. Remove the lead after flashing is done, otherwise the lamp won't boot in normal mode.

In the images below, you can see the first solution, using a breadboard.

Make a backup of the current firmware

Backing up the firmware makes it possible to revert to the original firmware, in case you have problems with the ESPHome firmware. The backup can be created using "esptool". Installation instructures can be found here:

https://github.com/espressif/esptool/blob/master/README.md#installation--dependencies

Here's an example on how to backup the original firmware from Linux. First, unplug your lamp's power supply, then start the esptool read_flash command:

python esptool.py -p /dev/ttyUSB0 read_flash 0x0 0x400000 original-firmware.bin

/dev/ttyUSB0 is the port of the USB adaper on Linux. You can find what port is used by the adapter by running dmesg after plugging in the USB device. On Windows this is often COM1, COM2 or COM3.

Now plug in the power supply. The output of esptool should now show that it connects to the lamp and downloads the firmware from it.

Caution: You will find the WLAN SSID and Password of the last used WiFi network in this file. Therefore, keep this backup in a safe place.

Restore the backed up firmware

In case you need to rollback to the lamp's original firmware at some point, here's an example of how to restore the original firmware from Windows, by fully flashing it back onto the lamp.

First, unplug your lamp's power supply, then start the esptool write_flash command:

python.exe .\esptool.py --chip esp32 --port COM3 --baud 115200 write_flash 0x00 original-firmware.bin

Make sure that GPIO0 is connected to GND and plug in the power supply. The output of esptool should now show that it connects to the lamp and uploads the firmware to it. Be patient after the upload reaches 100%. The output is silent for a while, but esptool tool is verifying if the firmware was uploaded correctly.

After the firmware upload completes, unplug the power, disconnect GPIO0 from GND and reconnect the power supply to boot into the restored firmware.

Flash new ESPHome firmware

Setup an ESPHome Project (see README.md),compile the firmware for the lamp and download the firmware.bin file to the device to which the serial adapter is connected.

You can flash the lamp using esphome or esptool. I would recommend using the esphome-flasher tool, which is a very easy to use GUI utility app for flashing ESPHome devices:

  • In the app, select the COM port of your serial adapter.
  • Also select the firmware.bin file to flash onto the lamp.
  • Power up the lamp with GPIO0 connected to GND.
  • Click the "Flash ESP" button to flash the firmware.

If you want to flash with esptool, you can use:

python.exe .\esptool.py --chip esp32 --port COM3 --baud 115200 write_flash 0x1000 <path\to\yourfirmware.bin>

After flashing, power down the lamp, disconnect GPIO0 from GND and reconnect the power to boot into the new ESPHome firmware.

From here on, it is possible to flash the lamp OTA (over the air, which means that the firmware is uploaded over WiFi) from ESPHome. Therefore, it is now time to tuck away or remove those soldered wires and add the bottom cover back on.

Troubleshooting flash

If you have A fatal error occurred: MD5 of file does not match data in flash!, then make sure you are powering the board using the lamp's own power adapter. We've seen these errors when trying to power the board using the 3.3V debug pad.

After seeing this error, user @tabacha was able to successfully flash his lamp using the regular power adapter and the tasmota boot loader using the following command:

python esptool.py --chip esp32  -p /dev/ttyUSB0 --baud 115200 --before default_reset --after hard_reset write_flash -z --flash_mode dout --flash_freq 40m --flash_size detect 0x1000 bootloader_dout_40m.bin 0x8000 partitions.bin 0xe000 boot_app0.bin 0x10000 ~/Downloads/schlafzimmerbedlight.bin

You will find the missing tasmota boot files here: https://github.com/arendst/Tasmota/tree/firmware/firmware/tasmota32/ESP32_needed_files

Note: user @tabacha was not able to use tasmota with the Bedside Lamp 2.

(remember that the esphome-flasher will give you a bit less of a hard-core experience during flashing)

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