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.

Report errors!

If you ever see an error within the range of 800 - 909, please report an issue at GitHub or on the support page.

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  • 903 (PANIC_REF_DELETED): an object reference was deleted and the object is no longer valid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

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