Build a Jumboshack sender

Turn a Raspberry Pi into a live feed of your geothermal heat pump. It reads your WaterFurnace Aurora control over its Modbus bus, once a minute, and streams the numbers to your Jumboshack dashboard. No soldering, no cloud middleman, and your data stays yours.

How it fits together

Two small pieces do the work. A USB-to-RS485 adapter gives the Pi a wire into your heat pump's Modbus bus, and a small pure-Python reader — light enough to run on a $15 Pi Zero 2 W over Wi-Fi — pulls the registers and streams each reading to Jumboshack over HTTPS:

  WaterFurnace Aurora ──(RS-485 / Modbus)── USB adapter ── Raspberry Pi
                                                              │
                                    fetch_modbus.py (native Python) → push (HTTPS)
                                                              │
                                                  ingest.jumboshack.com → your dashboard

It runs from cron every minute and is read-only — it only ever reads registers; it never sends anything back to your equipment. If the network hiccups, the reading is spooled and retried, so a blip never costs you data.

Everything here is off-the-shelf. If you already run a home lab, you probably have half of it in a drawer. Prices are ballpark.

1a · Pick a Raspberry Pi

The sender is featherweight — it reads the Modbus bus and POSTs once a minute — so even the smallest Pi is plenty. Choose on budget vs. convenience. The CanaKit kits bundle the microSD card, power supply, and case, so if you buy a kit you can skip section 1c entirely.

Availability note: the tiny Pi Zero kits have been frequently out of stock lately. If they are, the CanaKit Pi 3 B+ Starter Kit below is a reliable in-stock complete kit and works great. Stock and prices move — check the live links.

1b · The RS-485 tap (required)

1c · Add these only if you didn't buy a kit

As an Amazon Associate, Jumboshack earns from qualifying purchases. Some links above are affiliate links — if you buy through them we may earn a small commission at no extra cost to you. We only list parts we actually use.

Use the official Raspberry Pi Imager. Choose Raspberry Pi OS Lite (no desktop needed), and in the Imager's settings (the ⚙️ gear) before you write:

• Set a hostname you'll recognize, e.g. pi-geo
• Enable SSH and set a username/password (or drop in your SSH key)
• Enter your Wi-Fi details (or plan to use Ethernet)

Write the card, pop it in the Pi, and power up. Give it a minute, then connect:

ssh pi@pi-geo.local

The Aurora's AID Tool port is a standard RJ-45 jack carrying the RS-485 (Modbus) bus. The cleanest tap is a cheap Ethernet cable: plug it into the AID port, cut off the far end, and land the two data pairs on your USB-RS485 adapter's A (D+) and B (D−) screw terminals — keeping each pair twisted right up to the terminal for a clean signal.

  WaterFurnace AID Tool port — RJ-45 jack (standard T568B Ethernet colors)
  ─────────────────────────────────────────────────────────────────────────
    RJ-45 pin 1  white/orange ┐
    RJ-45 pin 3  white/green  ┴── twist ──►  RS-485 adapter:  A   (D+ / TXD+)

    RJ-45 pin 2  orange       ┐
    RJ-45 pin 4  blue         ┴── twist ──►  RS-485 adapter:  B   (D- / TXD-)

    other pins (24 VAC + unused) ─────────►  DO NOT connect or short
  ─────────────────────────────────────────────────────────────────────────
    RS-485 adapter ──── USB ────►  Raspberry Pi          →  /dev/ttyUSB0
    serial: 19200 baud · 8 data bits · ODD parity · 1 stop bit

Plug the adapter into the Pi. It should appear as /dev/ttyUSB0:

ls -l /dev/ttyUSB0

It's pure Python with a single dependency — no Ruby, no compilers, no proprietary tooling. Install Python and the Modbus library, then grab the open-source Jumboshack sender:

# Python 3 + the Modbus library
sudo apt update && sudo apt install -y python3 python3-pip
pip3 install minimalmodbus

# the open-source Jumboshack sender — read every line before you run it
git clone https://github.com/jumboshack/jumboshack-sender.git ~/jumboshack-sender
cd ~/jumboshack-sender

Smoke-test the wiring — read your unit once and print it:

python3 fetch_modbus.py --unit 1

If that prints your heat pump's temperatures instead of an error, your wiring is good and the hard part is done. 🎉 The reader is the same code we run on our own units — native Python, read-only, and validated field-for-field against the reference tooling.

a. Create a device token

In your Jumboshack Account, add a Location, then add a Device. You'll see a one-time token that looks like jsk_… — copy it now; it's shown only once. That token is what ties this Pi's data to your account.

b. Point the sender at your account

Drop your token and the ingest URL into ingest.env (it's gitignored — your token never leaves the Pi):

# ~/jumboshack-sender/ingest.env
INGEST_TARGETS=cloud
INGEST_URL_cloud=https://ingest.jumboshack.com/api/ingest/geothermal
INGEST_TOKEN_cloud=jsk_your_device_token_here

c. Dry-run first

Send one reading with ?validate=1 — it parses and checks your payload but stores nothing, so you can confirm the plumbing before you commit:

curl -X POST "https://ingest.jumboshack.com/api/ingest/geothermal?validate=1" \
  -H "Authorization: Bearer jsk_your_device_token_here" \
  -H "Content-Type: application/json" \
  --data @sample-reading.json

A "valid": true response means you're good. (Full payload shape and every accepted field are in the API guide.)

d. Schedule it every minute

Run crontab -e and add:

* * * * * /home/pi/jumboshack-sender/run.sh > /home/pi/jumboshack-sender/lastrun.log 2>&1

Within a minute, your dashboard lights up — live temperatures, power, pressures, flow, and a schematic of your loop. From here, History and Cost fill in on their own, day after day.

Troubleshooting

• No /dev/ttyUSB0? Re-seat the adapter; run dmesg | tail to see if it enumerated. Some adapters need the ch341 or FTDI driver (usually built into Raspberry Pi OS).
• fetch_modbus.py errors or times out? Almost always A/B swapped — try flipping the two data wires. Double-check GND and that the air handler is powered.
• 401 from the ingest API? The token is wrong or truncated — re-copy it from Account (add a fresh device if it's lost, since it's shown only once).
• 429? You're pushing too fast. One reading every 15–60s is ideal; the rate limit is 120/min per device.
• Readings arrive in bursts, or the dashboard goes stale then recovers? Usually WiFi power-save napping the Pi's radio. Turn it off — sudo iw dev wlan0 set power_save off — and make it persistent (a small @reboot cron or a systemd service). For an always-on sensor, wired Ethernet — or locking the Pi to one strong nearby access point — is even more reliable.