Raspberry-side server

The code that must run on the Raspberry Pi lives in the src_raspberry/ folder at the root of the plugin repository. It makes the bridge between the hardware (I2C sensors, GPIO actuators) and the network.

Note

This folder is an addition to the plugin and is not packaged: it is not part of the Python distribution of the PyMoDAQ plugin and does not modify it.

Layered architecture

The server is split into independent layers, each behind an interface; only main.py is not interchangeable, as it assembles the others.

 ZmqServer  ──►  JsonRequestHandler  ──►  HardwareBackend
(transport)       (request routing)       (component comm.)
      ▲                  ▲                       ▲
 ITransport       IRequestHandler         IHardwareBackend

• transport/ — communication with the PyMoDAQ client. zmq_server.py implements ZmqServer (ZeroMQ ROUTER); it only handles networking and framing.

• handlers/ — request handling. json_handler.py implements JsonRequestHandler (JSON decoding + routing). It performs no hardware access: everything is delegated to the backend.

• hardware/ — communication with the components. backend.py implements HardwareBackend (sensors + actuators); sensors.py holds the sensor drivers and the SENSOR_DRIVER_REGISTRY (AHT10, TMP102, EMC2101, PT-100, SIMULE); actuators.py holds the actuator drivers and the ACTUATOR_DRIVER_REGISTRY (PWM, DIGITAL); scanner.py detects I2C addresses.

• config.py — the description of the bench (pins, sensors, actuators). The only file to adapt from one bench to another (see Adapting the plugin to a bench).

• main.py — entry point: instantiates and wires the three layers (HardwareBackend → JsonRequestHandler → ZmqServer, port 5555 by default).

Quick installation (recommended)

A ready-to-use package installs the server on the Raspberry Pi and makes it start with the board — see Downloads (Raspberry Pi installation package).

1. Flash Raspberry Pi OS (64-bit), enable SSH, and connect the board to the network (Internet is needed during the installation).

2. Copy the package to the board and run the installer:

   scp install-dap-raspberry.zip <user>@<raspberry-ip>:~     # from the control computer
   unzip install-dap-raspberry.zip && cd install-dap-raspberry  # on the Raspberry Pi
   sudo bash install.sh
   

3. Report the IP address printed at the end in config_raspberry.toml on the control computer (address_Rasp), then sudo reboot if the installer asks for it (first activation of I2C).

The installer:

• installs the system packages (python3-venv, i2c-tools, pigpio), enables I2C and the pigpiod daemon;

• copies the server to /opt/pymodaq-raspberry with its own Python environment;

• installs the pymodaq-raspberry systemd service (starts at boot, restarts on failure);

• stops and disables the former pilotage.service (manual procedure below), which uses the same port;

• keeps an existing, modified config.py when run again (the new version is saved as config.py.new).

Options: --port <n> (other listening port), --user <account> (account running the server, default: the one calling sudo), --no-autostart. Without administrator rights, bash install.sh installs the server in ~/pymodaq-raspberry and starts it at boot through the user’s crontab, without changing the system.

Everyday commands:

sudo systemctl status pymodaq-raspberry     # state of the server
journalctl -u pymodaq-raspberry -f          # live log
sudo systemctl restart pymodaq-raspberry    # after editing config.py
sudo bash uninstall.sh                      # remove it (from the package folder)

Manual installation

1. OS Installation — Flash Raspberry Pi OS (64-bit) on a micro-SD card (8 GB min.). Connect via SSH and update the system: sudo apt update && sudo apt upgrade -y.

2. Enable I2C — sudo raspi-config → Interfacing Options → I2C.

3. pigpio daemon (hardware GPIO control):

   sudo apt-get update
   sudo apt-get install pigpio python3-pigpio
   sudo systemctl enable pigpiod
   sudo systemctl start pigpiod
   

4. Python dependencies:

   python3 -m venv .venv
   source .venv/bin/activate
   pip install -r requirements.txt
   

   Note

   If the requirements.txt file is missing, you can create it with the following content:

   Adafruit-Blinka>=8.69.0
   adafruit-circuitpython-busdevice>=5.2.15
   adafruit-circuitpython-connectionmanager>=3.1.6
   adafruit-circuitpython-emc2101>=1.2.12
   adafruit-circuitpython-register>=1.11.1
   adafruit-circuitpython-requests>=4.1.15
   adafruit-circuitpython-typing>=1.12.3
   Adafruit-PlatformDetect>=3.86.0
   Adafruit-PureIO>=1.1.11
   binho-host-adapter>=0.1.6
   board>=1.0
   pigpio>=1.78
   pyftdi>=0.57.1
   pyserial>=3.5
   pyusb>=1.3.1
   pyzmq>=27.1.0
   RPi.GPIO>=0.7.1
   smbus2>=0.6.0
   sysv_ipc>=1.2.0
   typing_extensions>=4.15.0
   

Running and Auto-start (systemd)

Manual test:

python main.py              # listens on port 5555
python main.py --port 5556  # other port (report it in the plugin configuration)
python main.py --verbose    # also logs every request and its response

Note

Automatic simulation mode — if the I2C bus is unreachable, if no sensor answers on it (bench not wired), or if the pigpio daemon is not running, the server falls back to simulation for the concerned part and logs a warning. The simulated temperatures and humidity follow a simple thermal model that reacts to the heater and the fan, and each simulated reading lasts as long as a real one. The server starts this way on any platform (Windows, macOS, Linux), so a whole demonstration can run on a single PC — see src_raspberry/README.md.

In production: the quick installation above creates the service for you. To do it by hand, create a systemd service file at /etc/systemd/system/pilotage.service:

[Unit]
Description=Thermal control ZeroMQ Server
After=network.target pigpiod.service

[Service]
ExecStart=/home/admin/PYMODAQ_PLUGIN_RASPPI3/PY_ENV/bin/python /home/admin/PYMODAQ_PLUGIN_RASPPI3/main.py
WorkingDirectory=/home/admin/PYMODAQ_PLUGIN_RASPPI3
StandardOutput=inherit
StandardError=inherit
Restart=always
User=admin

[Install]
WantedBy=multi-user.target

Warning

Make sure to put a space between the python binary and the path to main.py in ExecStart (two separate paths separated by a space).

Then, reload the daemon and start the service:

sudo systemctl daemon-reload
sudo systemctl enable pilotage.service
sudo systemctl start pilotage.service

Troubleshooting: * Check service status: sudo systemctl status pilotage.service (should be active (running)). * Check I2C devices on the bus: sudo i2cdetect -y 1.

Hardware Configuration (config.py)

The entire topology is centralized in src_raspberry/config.py:

I2C_BUS_ID      = 1
VENTILATEUR_PIN = 18     # PWM 25000 Hz
RESISTANCE_PIN  = 23     # PWM 100 Hz (via MOSFET)

CAPTEUR_AHT10   = 0x38   # rh_sortie
CAPTEUR_TMP102  = 0x48   # t_resistance
# 0x49 t_dissipateur, 0x4A t_entree, 0x4B t_sortie (TMP102)
CAPTEUR_EMC2101 = 0x4C   # T_emc

To change a pin or an address, modify ACTUATORS_CONFIG (actuators) or SENSORS_CONFIG (sensors) in this single file.