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. These are called panic codes.

basic.forever(function() {
    basic.showLeds(`
        # . . . #
        # # . # #
        . . . . .
        . # # # .
        # . . . #
        `)
    basic.pause(1000)
    basic.clearScreen()
    basic.showString("020")
})

Board system errors

The micro:bit system errors range between 01 - 99. For a full list of these codes, what they mean and what you can do to resolve them, visit the micro:bit guide to error codes.

• 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
• 30 (MICROBIT_HEAP_ERROR): a problem in the heap space
• 40 (MICROBIT_NULL_DEREFERENCE): there was a NULL dereference, the micro:bit tried to manage a invalid object pointer
• 42 (MICROBIT_SYSTEM_ERROR): there’s an error condition in the micro:bit system software
• 43 (MICROBIT_NO_RADIO): the micro:bit can’t enable the radio
• 50 (MICROBIT_HARDWARE_UNAVAILABLE_ACC): an error occurred with the micro:bit’s accelerometer component
• 51 (MICROBIT_HARDWARE_UNAVAILABLE_MAG): an error occurred with the micro:bit’s magnetometer component
• 90 (MICROBIT_HARDWARE_CONFIGURATION_ERROR): actual board hardware doesn’t match the configuration description
• 98 (MICROBIT_ASSERTION_FAILED): assertion failed, the condition in an assert was false

Memory errors

Memory error codes range from 800 - 909.

Garbage collector errors

Error codes generated from the garbage collector.

• 840: Allocation pointer is null or invalid
• 841: Garbage collection work queue error
• 843: VTable entry is not free
• 844: GC allocation failed for requested number of bytes
• 846: Invalid allocation thread
• 848: Allocation pointer beyond allocation header
• 849: Allocation pointer is null

Program access errors

• 901 (PANIC_INVALID_BINARY_HEADER): the type header for the object is not valid
• 902 (PANIC_OUT_OF_BOUNDS): the object data portion is greater than the length defined for it
• 903 (PANIC_REF_DELETED): an object reference was deleted and the object is no longer valid
• 904 (PANIC_SIZE): the object size doesn’t match the size defined for the type
• 905 (PANIC_INVALID_VTABLE): an object vtable is invalid or not initialized
• 906 (PANIC_INTERNAL_ERROR): an internal resource error
• 907 (PANIC_NO_SUCH_CONFIG): the specified device resource is not present
• 909 (PANIC_INVALID_ARGUMENT): the argument value is out of range or the type or format is invalid
• 927 (PANIC_VARIANT_NOT_SUPPORTED): using a v2 feature on a v1 board
• 928 (MICROBIT_LOG_FULL): The micro:bit failed to write to datalogger as the log was full

JavaScript runtime codes

Invalid cast codes

When the static type of x is a class C, the dynamic type of x isn’t C, and you try to access a field on x or call a method on x, you will get one of the following codes, depending on dynamic type of x.

• 980 (PANIC_CAST_FROM_UNDEFINED): when value of x is undefined
• 981 (PANIC_CAST_FROM_BOOLEAN): when value of x is true or false
• 982 (PANIC_CAST_FROM_NUMBER): when x is a number
• 983 (PANIC_CAST_FROM_STRING): when x is a string
• 984 (PANIC_CAST_FROM_OBJECT): when x is object of some type
• 985 (PANIC_CAST_FROM_FUNCTION): when x is a function
• 989 (PANIC_CAST_FROM_NULL): when x is null

See also

panic, assert