Espruino Memory Viewer

This tool allows you to connect to an Espruino/Bangle.js device via Web Bluetooth and then display the contents of RAM as a Network.

It’s a good way to look into your code and see if there’s anything obviously using memory that shouldn’t be.

To use it:

• Open this link
• Click Connect
• Wait…
• Then click and drag and use the mousewheel to zoom

• Clicking on a node will show you information about that node at the top, including a calculated path which may be able to show you where the variable is defined.

• RED are global and hidden objects in Espruino
• GREEN are functions
• GREY links are added between array/object elements to enforce ordering

Diff

After initially connecting, you might want to do something on your device that is causing memory usage to increase, and then click the Diff button. This will scan all memory again and will make all variables that were previously allocated grey (note that if variables have moved around, it is possible that new variables will be turned grey instead).

Garbage Collection

Before requesting the variables, EspruinoMemView triggers a garbage collect so that variables that are not needed are removed (which helps remove distracting information).

However, when doing Diff you can uncheck the GC? checkbox which will ensure a garbage collect isn’t done when the diff is created. This will allow you to see new ‘garbage’ (which will be noticeable by the way it’s not connected to anything else).

Why is there garbage? Espruino normally frees any ‘unreferenced’ variables, but if a datastructure is self-referential (for example a={}; a.b=a;) then Espruino won’t immediately detect this and will not free it until the available memory runs low and a GC pass is performed. You can detect self-referential datastructures by looking at the net for ‘loops’ of reference (eg a loop where the arrows all point in the same direction).

If you can find where the loop is, you may be able to modify your code such that the looping reference is removed before the datastructure becomes unused, which will then ensure that Garbage Collection has to happen less frequently.