Lab 4 - Using SciSDK in Python to Access the Threshold Discriminator Registers

In the Threshold Discriminator with Event Counter Lab (Lab 3), we designed an FPGA firmware on the DT1260 that implements:

• A threshold register (THRESHOLD)
• A reset register (RESET)
• A counter register (COUNTS)

…and we verified the design by programming the board, using the integrated Oscilloscope, and checking the threshold-crossing events in Sci-Compiler’s Resource Explorer.

Now, in this lab, we will access those same registers from a Python script using the SciSDK library. This lets us automate controlling and reading our threshold-based event counter.

Instructions

Install Requirements

1. Install and install the SciSDK library on your system.

   • For Windows, download the installer from the GitHub release page
   • For Linux, compile the source code from the GitHub repository

2. Install the SciSDK Python library from PyPI:

   pip install scisdk
   

1. Preparing the Correct JSON File

After compiling your Sci-Compiler project (and assigning addresses in the Memory Map), Sci-Compiler generates a JSON file (often named RegisterFile.json or similar). That file contains the actual register addresses that match your specific firmware build.

1. Locate the RegisterFile.json in your project library folder.
2. Copy it into your Python working directory.
3. If needed, rename it (e.g. RegisterFile.json), so you can easily reference it in your code.

Important: If you recompile the firmware, the register addresses (and the generated JSON) might change. Always use the latest JSON file that corresponds to the bitstream you programmed on your board.

2. Example Python Script

Below is a fully working Python script that demonstrates how to:

1. Connect to the DT1260 over USB (change "usb:10500" to your board’s serial number).
2. Set and Get the THRESHOLD register.
3. Reset the event counter.
4. Read the COUNTS register in a loop, once per second.

Python Code:

from scisdk.scisdk import SciSDK
from scisdk.scisdk_defines import *
import time

# 1. Initialize the SDK
sdk = SciSDK()

# 2. Add the DT1260 device
#    - "usb:10500" is the USB connection with serial number 10500.
#    - "dt1260" is the device model recognized by SciSDK.
#    - "./RegisterFile.json" is your JSON with the memory map from Sci-Compiler.
#    - "board0" is an alias for this device, used in subsequent register paths.
result = sdk.AddNewDevice("usb:10500", "dt1260", "./RegisterFile.json", "board0")
if result != 0:
    print("Error adding device:", sdk.s_error(result))
    exit()

# 3. Set the threshold register
threshold_value = 2300
result = sdk.SetRegister("board0:/Registers/THRESHOLD", threshold_value)
if result != 0:
    print("Error setting threshold:", sdk.s_error(result))
else:
    print(f"Threshold set to {threshold_value}")
    
# Optionally read back the threshold to confirm
result, threshold_value = sdk.GetRegister("board0:/Registers/THRESHOLD")
if result != 0:
    print("Error getting threshold:", sdk.s_error(result))
else:
    print(f"Threshold read back: {threshold_value}")

# 4. Reset the event counter (write 1 then 0)
result = sdk.SetRegister("board0:/Registers/RESET", 1)
if result != 0:
    print("Error writing RESET (1):", sdk.s_error(result))

result = sdk.SetRegister("board0:/Registers/RESET", 0)
if result != 0:
    print("Error writing RESET (0):", sdk.s_error(result))
else:
    print("Counter has been reset.")

# 5. Read the COUNTS register in a loop
while True:
    err, counts_value = sdk.GetRegister("board0:/Registers/COUNTS")
    if err != 0:
        print("Error reading COUNTS register:", sdk.s_error(err))
    else:
        print(f"COUNTS = {counts_value}")
    time.sleep(1)

Code Explanation

1. AddNewDevice: Tells SciSDK which board model you’re using and where to find the register address definitions (the JSON file).

2. SetRegister/GetRegister: Provide a path like “board0:/Registers/” to read or write that named 3.register from the firmware.

3. Threshold: We use THRESHOLD to set the threshold level for the FPGA comparator logic (as designed in Lab 3).

4. Reset: Writing 1, then 0 to the RESET register clears the counter.

5. Counts: The script continuously queries COUNTS to see how many events have occurred since the last reset.

Expected output: