2 docs tagged with "instrumentation"

Every figure in this folder so far has come from a datasheet table or from arithmetic built on one. Neither tells you what your board actually draws. A datasheet's Stop-mode current is measured on ST's own characterisation board, with nothing attached to the GPIOs, a specific silicon revision, and every peripheral in the state ST chose to test it in; your board has a pull-up ST did not model, a status LED that never got gated, and firmware that may or may not be entering the mode it claims to. Energy Budgets's entire arithmetic is only as good as the I_avg fed into it, and the only way to know that number is real is to measure it on the actual hardware running the actual release firmware — the warning on that page about a demo build with logging left on exists precisely because nobody measured until it was too late.

Embedded debugging goes wrong in a particular way. You have a symptom — the board hangs after eleven minutes, the sensor returns zeros every hundredth read, the current draw is four times what the datasheet promises — and you reach for the instrument you are most comfortable with rather than the one that can answer the question. Then you measure the wrong thing very carefully for a day.