ThermalTests

Software test, telemetry, and control prototyping for the SPICEsat thermal testbench.

Work done by Systems Integration & Test.

Hardware required

• Raspberry Pi 4 (Linux / Raspberry Pi OS)
• TMP-series I²C temperature sensors (TMP100 / TMP102; ADD0/ADD1 select the address)
• Heater patch / resistive heater (PWM through GPIO)

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Setting up on a Raspberry Pi, step by step

Follow these in order. Steps 1–5 are a one-time setup; after that you only need Step 7.

Want to run it on a laptop with no sensors? Skip to Running without any hardware.

Step 1 — Turn the Pi OFF

Unplug the power. Never move wires while the Pi is on.

Step 2 — Wire up the sensors

Every sensor shares the same four Pi pins. Wire them all in parallel:

Sensor pin	Goes to Pi pin	What it is
V+ (or VCC)	pin 1	3.3 volts (power)
GND	pin 6	ground
SDA	pin 3	data
SCL	pin 5	clock

Pin 1 is the corner pin closest to the SD card slot. The odd numbers (1, 3, 5) are all in the same row.

Each sensor needs its own address, chosen with its ADD0 and ADD1 pins. Two sensors sharing an address will not both show up. Both pins to GND gives 0x48; both to 3.3 V gives 0x4f. The usable range is 0x48–0x4f.

Step 3 — Power on and enable I2C

Plug the Pi back in, open a terminal, and run:

sudo raspi-config

Then: Interface Options → I2C → Yes → OK → Finish.

Reboot so the change takes effect:

sudo reboot

Step 4 — Check the Pi can see your sensors

4a. Do you already have the I2C tool?

i2cdetect -V

If that prints a version number, skip ahead. If it says command not found:

sudo apt install -y i2c-tools

4b. Is I2C actually switched on?

ls /dev/i2c-*

/dev/i2c-1 means yes. No such file or directory means Step 3 did not take — repeat it and make sure you reboot.

4c. Find your sensors.

i2cdetect -y 1

Every sensor you wired should appear as a number between 48 and 4f:

     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
40: -- -- -- -- -- -- -- -- 48 49 4a 4b -- -- -- --

If a sensor is missing here, the software will not find it either. Fix the wiring before going on.

Step 5 — Install the software

git clone https://github.com/rutgers-star/ThermalTests.git
cd ThermalTests

sudo apt install -y python3-venv

python3 -m venv .venv && source .venv/bin/activate

python -m pip install -r multi_sensor_telemetry/requirements.txt

That installs smbus2, the only third-party dependency. A plain virtual environment is enough — you do not need --system-site-packages.

Step 6 — Confirm the software sees the same sensors

cd multi_sensor_telemetry
python main.py --list

Found 4 TMP100 sensor(s) on I2C bus 1:
  0x48
  0x49
  0x4a
  0x4b

This list should match what i2cdetect showed in Step 4c. If it does, everything below will work.

Step 7 — Stream live temperatures

python main.py

One row per second, one column per sensor:

{'0x48': 21.438, '0x49': 20.812, '0x4a': 21.125, '0x4b': 20.938}

Press Ctrl-C to stop.

Step 8 — Log a run to CSV

python main.py --csv run1.csv --interval 5

That writes a row every 5 seconds to run1.csv until you press Ctrl-C:

timestamp,0x48,0x49,0x4a,0x4b
2026-10-13T14:02:11.431,21.438,20.812,21.125,20.938

To stop automatically after a set number of rows, add --rows:

python main.py --csv run1.csv --interval 5 --rows 720   # one hour at 5 s

Coming back later

The virtual environment has to be activated each time you open a new terminal:

cd ThermalTests && source .venv/bin/activate
cd multi_sensor_telemetry && python main.py

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Running without any hardware

Add --fake to any command and the code uses four simulated sensors and never touches I2C. This works on Windows, macOS, and Linux, and needs no pip install at all — simulation mode is pure standard library.

python main.py --fake --list
python main.py --fake
python main.py --fake --csv test.csv --rows 10 --interval 0.5

Run the test suite the same way, from the repository root:

python -B -m unittest discover -s multi_sensor_telemetry/tests -v

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All the options

--list                scan 0x48-0x4F, print what was found, exit
--fake                use simulated sensors, no I2C
--single              read one address instead of scanning
--address 0x4f        which address --single uses (default 0x4f)
--channel 1           I2C bus number (default 1)
--interval 5          seconds between printed/logged rows (default 1.0)
--csv [FILE]          append rows to a CSV log
--rows 100            stop after N rows (default 0 = until Ctrl-C)

Sensors always sample at 0.5 s internally; --interval only changes how often rows are printed and logged.

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If it does not work

What you see	What to do
i2cdetect shows no numbers	Turn the Pi off and recheck the four wires. A loose wire is the most common cause.
i2cdetect shows fewer sensors than you wired	Two sensors are probably set to the same address. Change one with its ADD0/ADD1 pins.
No such file or directory: /dev/i2c-1	I2C is not enabled. Redo Step 3, including the reboot.
ModuleNotFoundError: smbus2	The virtual environment is not active. Run source .venv/bin/activate.
PermissionError on /dev/i2c-1	Your user is not in the i2c group. Run sudo usermod -aG i2c $USER, then log out and back in.
No TMP100 sensors found on I2C bus 1	The software scanned but nothing answered. Check Step 4c first — if i2cdetect is empty too, it is the wiring.
An address disappears mid-run	That sensor stopped responding or went stale. See below.

About missing addresses

get_latest() deliberately omits a sensor that has errored, been stopped, or whose last good reading is older than max_age. A disconnected sensor disappears from the output instead of repeating its last temperature forever, so the PID controller can never act on a frozen reading. In the CSV, that address is left blank for those rows.

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Using it from your own code

This is how the PID controller consumes it. Run from the repository root:

from multi_sensor_telemetry import MultiTMP100
import time

m = MultiTMP100()            # add use_fake=True to run with no hardware
try:
    m.start()
    time.sleep(0.6)
    temps  = m.get_latest()  # {"0x48": 21.4, ...}  invalid sensors omitted
    status = m.get_status()  # temperature, timestamp, age, valid, error
finally:
    m.stop()

Temperatures are in °C. See multi_sensor_telemetry/README.txt for the full API notes, shutdown semantics, and CSV behaviour.