RTC Counter

Counts how many times the device has woken up from deep sleep. The counter is stored in RTCReal-Time Clock memory, so it survives deep sleep but resets on power loss. Uses the kv, schema, and sleep APIs.

Hardware

• Any ESP32 board
• USBUniversal Serial Bus cable

Code

import {rtcStorage} from 'mikro/kv/rtc'
import * as s from 'mikro/schema'
import {deepSleep, sleep} from 'mikro/sleep'

// Read the wake counter from RTC memory (survives deep sleep).
// optional() because the key may not exist on first boot.
const count = rtcStorage.createValue('count', {schema: s.optional(s.number())})

console.log(`Wake #${count.get() ?? 0}`)
console.log(`RTC memory: ${rtcStorage.info().used}/${rtcStorage.info().total} bytes used`)

// Increment and store back
count.update((n) => (n ?? 0) + 1).orPanic('failed to store count')

console.log('Waiting for a few seconds before going to deep sleep...')
await sleep(5000)

// Sleep for 15 seconds, then wake up again
console.log('Going to deep sleep for 15s...')
deepSleep({timer: 15_000})

Walkthrough

1. RTCReal-Time Clock-backed key/value. rtcStorage.createValue('count', {schema}) returns a typed handle whose value lives in RTCReal-Time Clock memory. optional(number()) makes the schema accept undefined so the first boot reads cleanly.

2. Read. count.get() returns the stored value or undefined. The ?? 0 defaults the first boot to 0.

3. Update. count.update(fn) reads, transforms, and writes atomically. Returns a Result, so .orPanic() halts with a clear message if the write fails.

4. Deep sleep. deepSleep({timer: 15_000}) powers down the CPUCentral Processing Unit for 15 seconds (the value is in milliseconds). RTCReal-Time Clock memory is preserved; everything else is lost. On wake, the script runs from the top.

Create project

pnpm

pnpm create mikro --template rtc-counter

npm

npm create mikro -- --template rtc-counter

yarn

yarn create mikro --template rtc-counter

bun

bun create mikro --template rtc-counter

Run it

pnpm

pnpm install
pnpm mikro flash  # only needed once per board
pnpm mikro dev

npm

npm install
npx mikro flash  # only needed once per board
npx mikro dev

yarn

yarn install
yarn mikro flash  # only needed once per board
yarn mikro dev

bun

bun install
bunx mikro flash  # only needed once per board
bunx mikro dev

The console shows Wake #0, then after each deep sleep cycle Wake #1, Wake #2, and so on. Power-cycle the board to reset the counter.

View source on GitHub