pxt-calliope/docs/device/error-codes.md

Error codes

Your micro:bit may encounter a situation that prevents it from running your code. When this happens, a frowny face will appear on your micro:bit screen (see picture) followed by an error number.

Below is a list of error numbers and what they mean:

• 10 (MICROBIT_I2C_LOCKUP): the micro:bit's I2C bus is not working
• 20 (MICROBIT_OOM): there is no free memory on the micro:bit

basic.showLeds(`
    # . . . #
    # # . # #
    . . . . .
    . # # # .
    # . . . #
    `)

See also

Run scripts on your micro:bit