Connect Device to Wi-Fi #

Any Wi-Fi board you flash, such as a Pico W or an ESP32, joins the site’s IoT SSID with your tenant’s Wi-Fi key. It makes no difference whether the device is your own or a pre-wired kit borrowed at a meetup (CARPE keeps those on its Example Project Kits page): once your key is on it, it is one of your devices.

This page covers only getting the device onto the network. Talking to the broker comes after, in Devices & MQTT, and the walkthrough does both end to end.

Where the device lands #

The SSID is shared by every tenant. The key is yours, and it is what makes the device one of yours ( Wi-Fi Keys).

1. Get your tenant’s key #

One key per tenant covers all your devices. If you already have one, reuse it.

resource "deevnet_iot_wifi_key" "devices" {
  tenant      = deevnet_tenant.this.name
  name        = "devices"
  trust_class = "iot"
}

output "device_wifi" {
  value     = { ssid = deevnet_iot_wifi_key.devices.ssid, psk = deevnet_iot_wifi_key.devices.psk }
  sensitive = true
}

terraform apply
terraform output -json device_wifi

Take the SSID from the output too, rather than typing DVNTM-IOT: another site names its IoT SSID differently.

2. Put it on the device #

Keep the key in a file of its own beside your code, and keep that file out of git.

Pico W, MicroPython. A secrets.py on the board:

SSID = "<device_wifi.ssid>"
PSK  = "<device_wifi.psk>"

and in main.py:

import network, time
from secrets import SSID, PSK

wlan = network.WLAN(network.STA_IF)
wlan.active(True)
wlan.connect(SSID, PSK)
while not wlan.isconnected():
    time.sleep(0.5)
print("on Wi-Fi:", wlan.ifconfig()[0])

ESP32, Arduino. A secrets.h beside the sketch:

#define WIFI_SSID "<device_wifi.ssid>"
#define WIFI_PSK  "<device_wifi.psk>"

and in the sketch:

#include <WiFi.h>
#include "secrets.h"

void setup() {
  Serial.begin(115200);
  WiFi.begin(WIFI_SSID, WIFI_PSK);
  while (WiFi.status() != WL_CONNECTED) delay(500);
  Serial.print("on Wi-Fi: ");
  Serial.println(WiFi.localIP());
}

void loop() {}

A borrowed kit’s own instructions say where its firmware expects the key. The idea is the same.

3. Check it joined #

Watch the serial console. The device should print an address between 10.20.30.100 and 10.20.30.200. If it does, the device is on your tenant’s key, and the next step is a broker account: Devices & MQTT.

When it doesn’t join #

• It never connects. The key or SSID is wrong. Copy both from terraform output again, and check nothing was trimmed or quoted twice
• The board has no Wi-Fi. A plain Pico, like the one in CARPE’s starter kit, has no radio; only a Pico W (or another Wi-Fi board) can join
• It joins but can’t reach the broker. That’s past Wi-Fi: the broker needs its own account, and TLS needs the site CA ( Devices & MQTT)
• It stopped working after a key rotation. Rotating the key drops every device holding the old one, until each is reflashed ( Wi-Fi Keys)

Handing back a borrowed device #

Your Wi-Fi key is shared by all your devices, so don’t rotate it to return one kit. Instead:

1. Wipe the key from the device: delete secrets.py, or reflash the kit’s reference firmware
2. Remove its broker account from your Terraform and terraform apply, if you gave it one

Removing the broker account blocks the device’s next connection, not the one already open, so power-cycle it too.