4.9 Low power

Outcome 9 of 12 in domain 4 · Digital and microcontrollers

Sleep modes, wake-up by interrupt or timer, a year’s energy budget.

My targets

I declare:

Measure a dev board’s consumption in standby and show that the LED and the board’s regulator dominate: the reason for the bare chip.
Put a chip into deep sleep and measure microamps with the method that suits (switched shunt or dedicated instrument).
Wake the chip by external interrupt and by timer, measure the time and the energy of the wake-up.
Draw up a sensor’s energy budget over a year: standby, wake-ups, radio transmission, and choose battery, supercapacitor or small panel.
Put the sensors and the radio to sleep too, not just the chip, and prove it by measurement.
Compare the sleep modes of two chip families (AVR, STM32 or RP2040) by what they keep powered and what it costs.
Diagnosis: a sensor "on a battery for a year" dead in a month, find the leak: floating pin, pull-up, regulator, radio that doesn’t sleep.