Lab: Wi-Fi, MQTT Connect, Publish, and Subscribe

Course 1 · Module 6 Type: Hands-on lab (network + broker + device) Suggested time: 2.5–3.5 hours

Read first: Lesson · Cheatsheet · ← Table of Contents · ← M05 · M07 BLE →

Note: the snippets in this lab use the API of the TESAIoT Bitstream firmware, which is not yet open source. See detail and equivalent examples in the public SDK in the note at the top of the lesson MQTT and MQTTs on an Edge Device

Useful references during the lab

Document	Use when
Lesson	`cm55_trigger_mqtt_*`, CONFIG, topics
Hackathon MQTT pages	`web-app/ex09`–`ex15`
Bitstream Studio	Starting the broker / MQTT tools
HiveMQ MQTT Essentials	Reviewing QoS / retain

Lab Goals

Join Wi‑Fi until the status is CONNECTED
Connect MQTT to the broker you choose
Publish a message or telemetry at least once
Subscribe (from the host or the device) and see the message
Explain the difference between MQTT vs MQTTs, and record the config values used
(Recommended) watch JSON telemetry from a sensor (continuing from M05)

Prerequisites

Have passed M05, at least able to read a sensor (for telemetry)
The room’s Wi‑Fi SSID / password (do not record it in Git)
The broker host/port you will use
A subscribe tool on the PC (MQTTX, mosquitto_sub, or the Hackathon web-app)

Do not publish a real password or certificate into a public report

Lab A — Wi‑Fi link (required)

Call cm55_trigger_connect or example_wifi_ui_connect, per the project
Read cm55_get_wifi_status until IPC_WIFI_LINK_CONNECTED
Record the SSID (no need to record the password)

Pass when: the Wi‑Fi link is ready before touching MQTT

Lab B — MQTT connect + status (required)

Set the policy so MQTT can be used (such as the factory default)
cm55_trigger_mqtt_connect
Read cm55_get_mqtt_status until state == CONNECTED (2)
Note the broker_host, port, tls, and effective_client_id

(void)cm55_trigger_mqtt_connect();
/* poll cm55_get_mqtt_status until connected or timeout */

Pass when: the status is CONNECTED and you have a client id to note

Lab C — Publish and observe (required)

Choose at least one path:

C1 Telemetry path

Turn on the sensor + the TELEMETRY_PUBLISH policy
Subscribe on the host to the topic bitstream/<MAC12>/sensors (or whatever topic you set)
Confirm JSON is coming in

C2 Explicit publish

Use either path (cm33_mqtt_stack_publish, or the Studio panel) to send {"hello":1}
See the message on a subscriber

Pass when: you see a payload on a host tool at least once

Subscribe on the device side to the actuators topic (or use the existing topic-table config)
From the host, publish a test command to that topic
Record how the device received it (a log / an LED / an event, per what the firmware supports)

Pass when: there is evidence a message from the cloud/host reached the device (or reached the stack’s log)

Lab E — Choose one (recommended)

E1 MQTT vs MQTTs table

Fill in a comparison table from your experiment, or from the documentation of the kit used: port, tls, CA

E2 Hackathon web MQTT

Run ex09–ex14 per the Hackathon README (a broker in the Studio if needed)

E3 Payload design

Design a JSON for an event from M05 (a temperature threshold/feature), then try publishing it once

Pass when: you submit a table/screenshot/short design file

Short report (10–15 lines)

The Wi‑Fi SSID (no password)
The broker host:port and tls 0/1
The client id / MAC topic used
Evidence of publish + subscribe
Limitations you observed (such as telemetry’s QoS, needing Wi‑Fi first)

Troubleshooting

Symptom	Approach
An MQTT error / it won’t connect	Wi‑Fi isn’t up yet · `MQTT_ENABLED` is off · the wrong host/port
Connects but no telemetry	The sensor isn’t publishing · `TELEMETRY_PUBLISH` is off · the wrong topic
TLS fails	The port isn’t 8883 · the CA doesn’t match the broker · the device’s clock is wrong (if certificate checking depends on it)
Subscribe sees nothing	A different MAC / a different topic prefix · a different broker
Auth fails	The username/password is empty or wrong

Submit checklist

Labs A–D passed
At least 1 item from Lab E
mqtt-cloud.md filled in
The short report has no secrets

Lesson · Cheatsheet · Table of Contents · M07 BLE →

Cite this lesson

If you teach from this lesson or reuse it in slides or documents, credit it with the text below. If you changed it, add (adapted) after the title.

"Lab: Wi-Fi, MQTT Connect, Publish, and Subscribe" from TESA Open Knowledge by the Thai Embedded Systems Association (TESA), https://github.com/tesaiot/tesa-qualification-program, licensed under CC BY-NC 4.0

Thai attribution: "แล็บ: Wi-Fi, MQTT connect, publish และ subscribe" จาก TESA Open Knowledge โดยสมาคมสมองกลฝังตัวไทย (Thai Embedded Systems Association: TESA) https://github.com/tesaiot/tesa-qualification-program สัญญาอนุญาต CC BY-NC 4.0

Lesson link: https://tesaiot.github.io/tesa-qualification-program/en/courses/firmware-sdk-edge-ai/m06-mqtt/l02-lab/

This lesson adapts the source below; keep its credit too.
https://github.com/drsanti/TESAIoT-Courses/blob/287c21814ba8c75f693136616dcd270349a15966/C1/M06/lab.md · Original content by Asst. Prof. Dr. Santi Nuratch (ผศ.ดร.สันติ นุราช), KMUTT. Course 1 (C1/) of drsanti/TESAIoT-Courses. TESA funded the work and holds the rights; published here under CC BY-NC 4.0. The upstream repository carries no licence file. Text kept faithful; structure, front matter, quizzes and notes added by TESA Open Knowledge.

Full guide: how to cite TESA

Content is licensed CC BY-NC 4.0. Reuse it non-commercially and credit the Thai Embedded Systems Association (TESA) every time. · How to cite TESA