On the very first batch of Neo Trellis M4 Express boards, the factory bootloader was not protected against accidental overwriting. Normally, the bootloader is unlikely to be damaged, but certain buggy programs and certain development environments might overwrite the bootloader. If you have one of these boards, we recommend you update the bootloader, which will protect it against overwriting as part of the updating process.
To see if your board needs updating, double-click the reset button, and look at the
INFO_UF2.TXT file in
TRELM4BOOT. If the bootloader version listed is earlier than "
UF2 Bootloader v2.0.0-adafruit.7", you may want to update.
Download the bootloader updater below. Double-click the reset button and wait for the
TRELM4BOOT drive to appear. Then drag or copy the updater
TRELM4BOOT. Wait for
TRELM4BOOT to reappear. Your bootloader is now protected against overwriting.
After updating, you'll need to reload CircuitPython or whatever other program was loaded on the board. Your
CIRCUITPY drive is not affected by the updater on NeoTrellis M4 Express, because it's on a separate SPI flash chip.