WiFi + HTTP

Connect to a WiFi network and make an HTTPHypertext Transfer Protocol request to a JSONJavaScript Object Notation APIApplication Programming Interface. Uses the wifi and http/request APIs.

Hardware

• Any ESP32 board with WiFi
• USBUniversal Serial Bus cable
• A WiFi network with internet access

Setup

Set your WiFi credentials as environment variables:

pnpm

pnpm mikro env set WIFI_SSID YourNetworkName --no-secret
pnpm mikro env set WIFI_PASSPHRASE

npm

npx mikro env set WIFI_SSID YourNetworkName --no-secret
npx mikro env set WIFI_PASSPHRASE

yarn

yarn mikro env set WIFI_SSID YourNetworkName --no-secret
yarn mikro env set WIFI_PASSPHRASE

bun

bunx mikro env set WIFI_SSID YourNetworkName --no-secret
bunx mikro env set WIFI_PASSPHRASE

Code

import {env} from 'mikro/env'
import {request} from 'mikro/http/request'
import {memoryUsage} from 'mikro/sys'
import {wifi} from 'mikro/wifi'

const ssid = env.require('WIFI_SSID')
const passphrase = env.require('WIFI_PASSPHRASE')

// Connect to WiFi
console.log(`Connecting to ${ssid}...`)
const connectResult = await wifi.connect({ssid, passphrase})
if (!connectResult.ok) {
  console.error('WiFi connect failed:', connectResult.error)
} else {
  console.log('Connected! IP: %s', connectResult.value.ip)

  // Request JSON from an API
  const result = await request('https://httpbingo.org/json')
  if (result.ok) {
    if (!result.value.ok) {
      console.error(`HTTP error: ${result.value.status}`)
    } else {
      const data = await result.value.json()
      if (!data.ok) {
        console.error('Body decode failed:', data.error)
      } else {
        console.log('Fetched: %o', data.value)
      }
    }
  } else {
    console.error('Request failed:', result.error)
  }
}

const mem = memoryUsage()
console.log('free heap: %dKB', (mem.heapTotal - mem.heapUsed) / 1000)

Walkthrough

1. Country code. wifi.country must be set before connecting. This configures the regulatory domain for your region's WiFi channels.

2. Environment variables. WiFi credentials come from env.require(), which panics with a clear message if a variable is missing. Environment variables are stored in NVSNon-Volatile Storage on device. Set them with mikro env set.

3. Connect. wifi.connect() returns a Promise<Result>. The outer Result tells you if the connection succeeded; the value contains your IP address.

4. Request. request() also returns a Promise<Result>. Two levels of error checking:

   • result.ok: did the network request succeed at all?
   • result.value.ok: was the HTTPHypertext Transfer Protocol status in the 2xx range?

5. Memory. Prints free heap after the request completes, useful for tracking memory on constrained devices.

Create project

pnpm

pnpm create mikro --template wifi-fetch

npm

npm create mikro -- --template wifi-fetch

yarn

yarn create mikro --template wifi-fetch

bun

bun create mikro --template wifi-fetch

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 output shows the WiFi connection, the fetched JSONJavaScript Object Notation data, and memory usage.

View source on GitHub