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Electr 101

Electr 101

June 24, 2026

TL;DR

Someone is already doing this!

Intro

I saw a podcast on the beach and

https://github.com/diodeinc/pcb

Conclusions

FAQ

IoT MQTT

So:

  • connected client from 192.168.1.15 = yes
  • active Pico message traffic right now = not observed in the brief trace

If you want, I can keep a live trace running for longer or check the exact topic the Pico should be publishing to.

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› can you share with me the commands you run on the container to confirmed all that?

• Yes. These are the commands I ran from the host to confirm it:

docker ps –format ’table {{.Names}}\t{{.Image}}\t{{.Status}}\t{{.Ports}}' docker ps -a –format ’table {{.Names}}\t{{.Image}}\t{{.Status}}\t{{.Ports}}'

docker inspect -f ‘Status={{.State.Status}} Health={{if .State.Health}}{{.State.Health.Status}}{{else}}none{{end}} RestartCount={{.RestartCount}} StartedAt={{.State.StartedAt}}’ emqx docker logs –tail 40 emqx docker logs –since 1h emqx | tail -n 50 docker inspect -f ‘LogPath={{.LogPath}}’ emqx

docker exec emqx sh -lc ’ls -1 /opt/emqx/bin 2>/dev/null && echo — && /opt/emqx/bin/emqx_ctl status 2>/dev/null || true’ docker exec emqx sh -lc ‘/opt/emqx/bin/emqx_ctl help | sed -n “1,240p”’ docker exec emqx sh -lc ‘/opt/emqx/bin/emqx_ctl broker stats 2>&1 | sed -n “1,200p”’ docker exec emqx sh -lc ‘/opt/emqx/bin/emqx_ctl topics list 2>&1 | sed -n “1,200p”’ docker exec emqx sh -lc ‘/opt/emqx/bin/emqx_ctl retainer info 2>&1 | sed -n “1,120p”’ docker exec emqx sh -lc ‘/opt/emqx/bin/emqx_ctl retainer topics 1 1000 2>&1 | sed -n “1,200p”’ docker exec emqx sh -lc ‘/opt/emqx/bin/emqx_ctl clients list 2>&1 | sed -n “1,200p”’ docker exec emqx sh -lc ‘/opt/emqx/bin/emqx_ctl subscriptions list 2>&1 | sed -n “1,200p”’ docker exec emqx sh -lc ‘/opt/emqx/bin/emqx_ctl clients show e66141040370772c 2>&1 | sed -n “1,200p”’ docker exec emqx sh -lc ‘/opt/emqx/bin/emqx_ctl clients show mqttjs_d61ad246 2>&1 | sed -n “1,200p”’ docker exec emqx sh -lc ‘/opt/emqx/bin/emqx_ctl topics show pico/temperature/dht22 2>&1 | sed -n “1,200p”’ docker exec emqx sh -lc ‘/opt/emqx/bin/emqx_ctl topics show pico/humidity/dht22 2>&1 | sed -n “1,200p”’

docker exec emqx sh -lc ‘/opt/emqx/bin/emqx_ctl trace start topic pico/temperature/dht22 /tmp/pico-temp.trace info json 2>&1 | sed -n “1,120p”’ sleep 5; docker exec emqx sh -lc ‘wc -c /tmp/pico-temp.trace 2>/dev/null; echo —; sed -n “1,120p” /tmp/pico-temp.trace 2>/dev/null’

docker exec emqx sh -lc ‘/opt/emqx/bin/emqx_ctl trace stop topic pico/temperature/dht22 >/dev/null 2>&1; /opt/emqx/bin/emqx_ctl trace start topic pico/# /tmp/pico-all.trace info json 2>&1 | sed -n “1,120p”’ sleep 5; docker exec emqx sh -lc ‘wc -c /tmp/pico-all.trace 2>/dev/null; echo —; sed -n “1,120p” /tmp/pico-all.trace 2>/dev/null’

A couple of the key ones:

  • emqx_ctl clients list to see connected clients
  • emqx_ctl topics list to see active topics in broker state
  • emqx_ctl trace start topic … to watch live publishes

docker exec emqx sh -lc ‘/opt/emqx/bin/emqx_ctl clients list’ docker exec emqx sh -lc ‘/opt/emqx/bin/emqx_ctl topics list’ docker exec emqx sh -lc ‘/opt/emqx/bin/emqx_ctl trace start topic pico/# /tmp/pico.trace info json’

To check whether messages arrived after starting the trace:

sleep 5 docker exec emqx sh -lc ‘wc -c /tmp/pico.trace; echo —; sed -n “1,120p” /tmp/pico.trace’

To stop the trace:

docker exec emqx sh -lc ‘/opt/emqx/bin/emqx_ctl trace stop topic pico/#’

If you want a single command for live monitoring, I can give you a one-liner that loops and shows new trace output as it lands.

The usual way is to open a long-lived subscriber and keep it connected.

If you have mosquitto_sub installed:

mosquitto_sub -h 127.0.0.1 -p 1883 -t ‘pico/#’ -v

That will stay open and print every message on any pico/… topic.

Useful variants:

  • All topics:

    mosquitto_sub -h 127.0.0.1 -p 1883 -t ‘#’ -v

  • Only one sensor topic:

    mosquitto_sub -h 127.0.0.1 -p 1883 -t ‘pico/temperature/dht22’ -v

  • Show connection/debug details:

    mosquitto_sub -h 127.0.0.1 -p 1883 -t ‘pico/#’ -v -d

If you need TLS on EMQX:

mosquitto_sub -h 127.0.0.1 -p 8883 –cafile ca.crt -t ‘pico/#’ -v

If mosquitto_sub is not installed, I can give you the equivalent using a container or another MQTT client.

I found it here:

  • poc/iot-rpi-dht-insulation/ingester/data/readings.sqlite

What I verified:

  • It has a readings table.
  • It currently contains 40 rows.
  • The newest rows are from 2026-06-07, including:
    • pico/temperature/dht22
    • pico/humidity/dht22
    • pico/temperature/internal
    • esp32/temperature/dht11
    • esp32/humidity/dht11
mosquitto_sub -h 127.0.0.1 -p 1883 -t 'pico/temperature/dht22' -v
mosquitto_sub -h 127.0.0.1 -p 1883 -t 'pico/humidity/dht22' -v

Tomatoes

Selfhosted ConnectivityAerospace 101 x DIY Drone