97 lines
2.6 KiB
Python
Executable File
97 lines
2.6 KiB
Python
Executable File
#!/usr/bin/env python3
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# Copyright (c) 2023 Google LLC
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# SPDX-License-Identifier: Apache-2.0
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"""
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Zephyr's NTC Thermistor DTS Table generator
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###########################################
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This script can be used to generate an NTC thermistor DTS node with a
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"zephyr,compensation-table" property. This uses the Beta Parameter Equation
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https://devxplained.eu/en/blog/temperature-measurement-with-ntcs#beta-parameter-equation
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Look-up the following electrical characteristics in the thermistor's data sheet:
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Nominal resistance (R25) - The thermistor's resistance measured at 25C
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Beta value (25/85) - This is the resistance value at 25C and at 85C
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Usage::
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python3 ntc_thermistor_table.py \
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-r25 10000 \
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-b 3974 > thermistor.dtsi
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"""
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import argparse
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import os
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import math
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def c_to_k(c: float):
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""" Convert Celicius to Kelvin """
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return c + 273.15
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def beta_equation_calc_resistance(r25, beta, temp_c):
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t0_kelvin = c_to_k(25)
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exp = beta * ((1 / c_to_k(temp_c)) - (1 / t0_kelvin))
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resistance = r25 * math.exp(exp)
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return resistance
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def main(
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r25: float, beta: float, interval: int, temp_init: int, temp_final: int
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) -> None:
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temps_range = range(temp_init, temp_final + interval - 1, interval)
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print(f"/* NTC Thermistor Table Generated with {os.path.basename(__file__)} */\n")
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print(
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f"thermistor_R25_{int(r25)}_B_{int(beta)}: thermistor-R25-{int(r25)}-B-{int(beta)} {{"
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)
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table = []
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for temp in temps_range:
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resistance = beta_equation_calc_resistance(r25, beta, temp)
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table.append(f"<({int(temp)}) {int(resistance)}>")
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tbl_string = ',\n\t\t'.join(table)
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print(f"\tzephyr,compensation-table = {tbl_string};")
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print(f"}};")
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if __name__ == "__main__":
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parser = argparse.ArgumentParser("NTC Thermistor generator", allow_abbrev=False)
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parser.add_argument(
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"-r25", type=float, required=True, help="Nominal resistance of thermistor"
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)
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parser.add_argument(
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"-b", "--beta", type=float, required=True, help="Beta(25/85) value"
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)
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parser.add_argument(
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"-i",
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"--interval",
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type=int,
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required=False,
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help="Generated table interval",
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default=10,
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)
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parser.add_argument(
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"-ti",
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type=int,
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required=False,
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help="First temperature",
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default=-25,
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)
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parser.add_argument(
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"-tf",
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type=int,
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required=False,
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help="Final temperature",
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default=125,
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)
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args = parser.parse_args()
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main(args.r25, args.beta, args.interval, args.ti, args.tf)
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