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Refactor: Replace magic numbers with constants in ScienceLab #277

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Refactor: Replace magic numbers with constants in ScienceLab #277

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e02b8a4
Refactor: Replace temperature and ADC magic numbers with constants
TejasAnalyst Feb 20, 2026
8780e27
Refactor: Add validation for current source in temperature lookup
TejasAnalyst Feb 20, 2026
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31 changes: 20 additions & 11 deletions pslab/sciencelab.py
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,17 @@
from pslab.instrument.power_supply import PowerSupply
from pslab.instrument.waveform_generator import PWMGenerator, WaveformGenerator

# --- Hardware Constants ---
ADC_VMAX = 3.3 # Maximum voltage for ADC
ADC_RESOLUTION = 12 # ADC resolution in bits

# --- Internal Temperature Sensor Calibration ---
# Constants for different current sources (1, 2, and 3)
TEMP_CALIB = {
1: {"offset": 646.0, "slope": 1.92}, #
2: {"offset": 701.5, "slope": 1.74}, #
3: {"offset": 760.0, "slope": 1.56}, #
}

class ScienceLab:
"""Aggregate interface for the PSLab's instruments.
Expand Down Expand Up @@ -47,16 +58,15 @@ def __init__(self, device: ConnectionHandler | None = None):
@property
def temperature(self):
"""float: Temperature of the MCU in degrees Celsius."""
# TODO: Get rid of magic numbers.
# Magic numbers resolved using global TEMP_CALIB dictionary
cs = 3
V = self._get_ctmu_voltage(0b11110, cs, 0)

if cs == 1:
return (646 - V * 1000) / 1.92 # current source = 1
elif cs == 2:
return (701.5 - V * 1000) / 1.74 # current source = 2
elif cs == 3:
return (760 - V * 1000) / 1.56 # current source = 3

# Clean lookup from global constants
cal = TEMP_CALIB.get(cs)
if cal is None:
raise ValueError(f"Unsupported current source: {cs}")
return (cal["offset"] - V * 1000) / cal["slope"]

def _get_ctmu_voltage(self, channel: int, current_range: int, tgen: bool = True):
"""Control the Charge Time Measurement Unit (CTMU).
Expand Down Expand Up @@ -94,9 +104,8 @@ def _get_ctmu_voltage(self, channel: int, current_range: int, tgen: bool = True)
self.device.send_byte((channel) | (current_range << 5) | (tgen << 7))
raw_voltage = self.get_int() / 16 # 16*voltage across the current source
self.device.get_ack()
vmax = 3.3
resolution = 12
voltage = vmax * raw_voltage / (2**resolution - 1)
# Use global hardware constants instead of local magic numbers
voltage = ADC_VMAX * raw_voltage / (2**ADC_RESOLUTION - 1)
return voltage

def _start_ctmu(self, current_range: int, trim: int, tgen: int = 1):
Expand Down