IceTop Viewer is a high-performance Raspberry Pi visualization system for IceCube/IceTop neutrino event data. It drives a large-scale physical display (typically an LED array representing South Pole detector stations) using complex multiplexing and hardware-timed PWM.
The project overcomes the GPIO limitations of the Raspberry Pi by using a Multiplexed Waveform approach. Instead of driving each LED individually, it groups them into channels and cycles through them at high speed.
- Library: Powered by
pigpio, leveraging thepigpioddaemon for DMA-based hardware PWM and waveform generation. This ensures flicker-free performance and precise timing unaffected by system load. - Refresh Logic: The system constructs generic waveforms (
pigpio.pulse) that combine both the channel selection (via demux) and the data payload (via PWM brightness levels) in a single sequence.
The system uses 17 GPIO pins (BCM numbering) to control a large array of stations:
| Function | GPIO Pins (BCM) | Description |
|---|---|---|
| Channel Select | 17, 27, 22 | 3-bit address lines for a 3-to-8 demultiplexer. |
| Data / PWM | 4, 26, 3, 10, 9, 11, 5, 6, 13, 19, 14, 15, 18, 23 | 14 independent data lines for driving LEDs. |
- Data Ingestion: Loads
.txtevent files containing station ID, DOM info, energy, and timestamps. - Mapping: Uses
81_pin_table.txtto resolve physical station IDs to specific (Pin, Channel) pairs. - Normalization: Scaler functions map raw energy values to duty cycles (0-100%) and relative time to simulation frames.
- Waveform Construction:
event_builder.pydynamically generatespigpiowaveforms for each step of the simulation, updating the entire display at a target refresh rate of 256Hz.
- pigpiod: Must be installed and running (
sudo systemctl enable pigpiod && sudo systemctl start pigpiod). - Python 3: Requires
numpy,pigpio, andtkinter.
- Ensure the hardware is connected to the specified GPIO pins.
- Run the main builder:
python3 event_builder.py. - Select a data file (e.g., from the
data/directory) and set the simulation duration.
Developed for the IceCube Neutrino Observatory visualization project.
Testing the initial output pins from the Raspberry Pi to ensure correct voltage and signal stability.
First successful implementation of the 8-channel multiplexing cycle.
Refining the pigpio waveform timing to eliminate flicker and achieve a stable 256Hz refresh rate.
Animating a 16-LED test array with pre-recorded IceTop event data.
Moving the circuitry to permanent breadboards and preparing the custom housing for the South Pole station array.
