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 followed by an error number.

Whenever this happens, you should:

• Press the reset button on the back of the device to restart your program.
• Flash the script to your micro:bit again.

If the problem persists please report the issue to us.

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

Hardware errors

Error number	What this means
10	The micro:bit's I2C bus is not working. The device might be physically damaged.
20	There is no free memory on the micro:bit. Your program might be too complex or contain a lot of large variables. Try reducing your code by making functions out of large sections.
30	Corruption detected in the micro:bit heap space (memory allocated usually for the storage of variables). Try flashing a different .hex file to your device
40	Your micro:bit can't execute your script properly. Flash a different .hex file to it, then try flashing and running your previous script again.
42	Your micro:bit can't execute your script properly. Flash a different .hex file to it, then try flashing and running your previous script again.
43	An error occurred with the micro:bit's radio component.
50	An error occurred with the micro:bit's accelerometer component.
51	An error occurred with the micro:bit's magnetometer component.
98	Assertion failed. A MakeCode error that occurs when the condition in an assert was false.

MakeCode Editor errors

Error codes generated from the MakeCode Editor. In all these cases, please report the error to us, or if you are comfortable using Github, submit an issue on the code repository.

Garbage collector errors

Error number	What this means
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

Error number	What this means
901	The type header for the object is not valid.
902	The object data portion is greater than the length defined for it.
903	An object reference was deleted and the object is no longer valid.
904	The object size doesn’t match the size defined for the type.
905	An object vtable is invalid or not initialized.
906	An internal resource error.
907	The specified device resource is not present.
909	The argument value is out of range or the type or format is invalid.

JavaScript runtime codes

These occur for example, 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.

Error number	What this means
980	When value of x is undefined.
981	When value of x is true or false.
982	When x is a number.
983	When x is a string.
984	When x is object of some type.
985	When x is a function.
989	When x is a null.