crosspoint-reader/docs/fix-bricked-xteink.md

Recovering a Bricked Xteink

This guide covers installing CrossPoint on an Xteink that's bricked, or stuck on firmware with no path to flash a replacement. It works by writing firmware directly to the SPI flash chip with an external programmer, bypassing the ESP32-C3 entirely.

If your device isn't USB-locked, flash it over USB instead — it's safer and much less invasive. What follows should only be a last resort.

Example: a device stuck on Biscuit firmware, unresponsive to a normal USB flash.

Required Tools

• Acetone or another nail polish remover.
• A SPI flash programmer. On this guide we use a CH341a; A Bus Pirate, Raspberry Pi/Pico or suitable Arduino, also works.
• Programmer software. flashrom (with libftdi) work on all OSs.
• esptool.py, but only if you intend to dump firmware from another device to use as your source image.

Before You Start

• Lithium batteries are dangerous, do not short or puncture. Be careful.
• The display is fragile, don't bend or flex it. do not force the ZIF connector.
• There is no undo here. A mis-wired clip or a short circuit can turn a bricked device into a dead one. Proceed at your own risk.

Procedure

1. Obtain a Firmware Image

Two options:

• Use the backup provided by @Uri-Tauber at crosspoint-reader/docs/images/spiflash/crosspoint_spiflash_backup.tar.xz, and extract the .bin file.
• Dump one yourself from a working, unlocked device over USB:
  • Turn the device on, connect the USB cable and do:

  ~$ pio pkg exec -p tool-esptoolpy -- esptool.py --chip esp32c3 -p /dev/ttyACM0 -b 921600 read_flash 0x000000     0x1000000 crosspoint_backup.bin
   # or
  ~$ esptool.py --chip esp32c3 -p /dev/ttyACM0 -b 921600 read_flash 0x000000 0x1000000 crosspoint_backup.bin
  

2. Disconnect Power Sources and Accessories

• Remove and set the SD card aside for reinsertion later.
• Remove any USB cable.
• Confirm nothing else is supplying power to the board.

3. Remove the Screen

Ordinary nail polish remover softens the adhesive under the screen's edges — it takes some patience, and there's no clean way around that.

• In a well ventilated space, free of any ignition source, apply acetone or nail polish remover to the borders of the screen.
• Check it from time to time, make sure the borders of the screen stay wet for around 2 hours.
• Start to pry open from a lower corner, and move around.
• If necessary, use a non-conductive tool to help you.
• Flip open the ZIF connector to release the screen from the board.

4. Disconnect the Battery

Cut a single battery wire close to the board, then cover the cut end with tape to prevent shorting.

5. Hold the Reset Button Down

Keeping reset held prevents the ESP32-C3 from interfering with SPI communication during the read/write. A piece of pointed plastic works well as a holder.

6. Attach the Test Clip

Connect the test clip to the flash chip before connecting the programmer to USB. Notes:

• The clip's red wire aligns with pin 1, marked with a dot on both the chip and the board silkscreen.
• Confirm each lead is making contact with a chip pin and not the epoxy body.
• If the programmer has a voltage selector, set it to 3.3V.
• Verify no other power source is connected — use a multimeter if there's any doubt.

7. Connect the Programmer to the PC

8. Verify the Connection by Reading Twice

Read the chip twice and compare hashes. If they don't match, something in the clip connection is off — fix that before writing anything to the chip.

~$ sudo flashrom --programmer ch341a_spi -r backup_0.bin
    [...]
    Reading flash... done.
~$ sudo flashrom --programmer ch341a_spi -r backup_1.bin
    [...]
    Reading flash... done.
    # lets compare the hashes from the back ups
~$ md5sum backup_0.bin
    211522e56616ea46ac9bcf82d3451eb2  backup_0.bin
~$ md5sum backup_1.bin
    211522e56616ea46ac9bcf82d3451eb2  backup_1.bin

9. Flash the Chip

~$ sudo flashrom --programmer ch341a_spi -w crosspoint_backup.bin
    [...]
    Reading old flash chip contents... done.
    Erasing and writing flash chip... Erase/write done.
    Verifying flash... VERIFIED.

10. Power and Test The Device

• Disconnect the programmer from the USB port.
• Remove the test clip.
• Release the reset button.
• Reinsert the SD card.
• Reconnect the screen.
• Power the device via USB cable, no need to solder the battery yet.
• Press the power button for a couple seconds.

If CrossPoint boots successfully, the device can be fully reassembled.