Lab 9 - Reading and Plotting Two Spectra (ToT and ToF)

In Measuring Time‐of‐Flight (ToF) and Time‐over‐Threshold (ToT) (Lab 8), we added firmware blocks to measure Time-over-Threshold (ToT) and Time-of-Flight (ToF). Below is a Python script (lab9_read_spectra.py) that resets both spectra, accumulates data for a fixed interval (10 seconds), and plots them side by side in Matplotlib.

Firmware Recap

From Lab 8, the design includes:

• A Spectrum_0 component for the ToT histogram.
• A TOF_0 component for the Time-of-Flight histogram.

Each spectrum block accumulates counts in bins corresponding to the measured ToT or ToF values.

Script Explanation

1. Initialization

   • We create a SciSDK instance and connect to the DT1260 using sdk.AddNewDevice("usb:10500", ...).
   • Adjust the serial number (10500) and the JSON file name (RegisterFile.json) for your setup.

2. Spectra Setup

   • We set some parameters (e.g., rebin, limitmode) to ensure normal operation.
   • We allocate two buffers: one for Spectrum_0 (ToT) and one for TOF_0 (ToF).

3. Reset & Start

   • We execute the reset command on both spectrum components. This clears the histogram memory.
   • Then we use start to enable data accumulation.

4. Accumulate Data

   • The script sleeps for 10 seconds (time.sleep(10)), giving the FPGA time to fill the histograms with events.

5. Read & Plot

   • We call sdk.ReadData("board0:/MMCComponents/Spectrum_0", buffer_tot) to read the ToT histogram into buffer_tot.
   • We do the same for TOF_0.
   • We extract the valid_bins and data arrays and plot them in two subplots:
     • Left: ToT Spectrum
     • Right: ToF Spectrum

6. Cleanup

   • Finally, we detach the device (sdk.DetachDevice("board0")) after plotting.

Usage

1. Compile & Program the Lab 8 firmware onto your DT1260.
2. Verify you have the matching RegisterFile.json generated by Sci-Compiler for that firmware version.
3. Install Python dependencies (e.g., pip install scisdk matplotlib).
4. Edit the code to use the correct serial number and JSON file path.
5. Run the script:

   python lab8_read_two_spectra.py
   

6. After 10 seconds, you should see two histograms side by side in a Matplotlib window.

Expected Results

• ToT Spectrum (Spectrum_0):
  Shows how long signals remained above threshold. Strong, stable pulses typically form a peak in the distribution.

• ToF Spectrum (TOF_0):
  Shows the time delay between T0 and the main signal crossing threshold. If you vary the external delay or signal timing, this peak will shift.

Combining the two measurements gives a powerful way to characterize both amplitude (via ToT) and timing (via ToF) of your pulses, all within the same FPGA firmware on the DT1260.