That is not possible on the Spark core without an external voltage reference due to the differences in how the ADCs work.
There are lots of current and battery monitoring ICs these days that might be a better fit for your project. Here is one:
That is not possible on the Spark core without an external voltage reference due to the differences in how the ADCs work.
There are lots of current and battery monitoring ICs these days that might be a better fit for your project. Here is one: