WP 34S and 31S bugs and fixes

[Marcus von Cube]

(02-08-2017 06:49 AM)Paul Dale Wrote:  Marcus is the battery voltage level expert from the 34S team.

Maybe my answer is a bit late but here it is:

BATT only reports the internal value so it does not consume any additional power for doing the measurement. The value is derived continuously from a circuit that compares the actual supply voltage to a given threshold. To determine the voltage the threshold is modified until a change in the comparator status bit is detected.

Since the answer is not delivered immediately by the hardware, the software has to wait some time before the readout. While the processor is running a heart beat interrupt is active which performs, among other things like the keyboard scan, the voltage measurement.