scripts: Create a script to generate an NTC thermistor R/T table

Script to generate an R/T table in device tree format given
R25 and Beta values.

Signed-off-by: Al Semjonovs <asemjonovs@google.com>

scripts/utils/ntc_thermistor_table.py

@@ -0,0 +1,101 @@
+#!/usr/bin/env python3
+
+# Copyright (c) 2023 Google LLC
+# SPDX-License-Identifier: Apache-2.0
+
+"""
+Zephyr's NTC Thermistor DTS Table generator
+###########################################
+
+This script can be used to generate a "zephyr,thermistor-rt-table" compatible
+Device Tree node for NTC thermistors.  This uses the Beta Parameter Equation
+
+https://devxplained.eu/en/blog/temperature-measurement-with-ntcs#beta-parameter-equation
+
+Look-up the following electrical characteristics in the thermistor's data sheet:
+    Nominal resistance (R25) - The thermistor's resistance measured at 25C
+    Beta value (25/85) - This is the resistance value at 25C and at 85C
+
+Usage::
+
+    python3 ntc_thermistor_table.py \
+        -r25 10000                  \
+        -b 3974 > thermistor.dtsi
+
+"""
+
+import argparse
+import os
+import math
+
+def c_to_k(c: float):
+    """ Convert Celicius to Kelvin """
+    return c + 273.15
+
+def beta_equation_calc_resistance(r25, beta, temp_c):
+    t0_kelvin = c_to_k(25)
+
+    exp = beta * ((1 / c_to_k(temp_c)) - (1 / t0_kelvin))
+    resistance = r25 * math.exp(exp)
+
+    return resistance
+
+
+def main(
+    r25: float, beta: float, interval: int, temp_init: int, temp_final: int
+) -> None:
+    temps_range = range(temp_init, temp_final + interval - 1, interval)
+
+    print(f"/* NTC Thermistor Table Generated with {os.path.basename(__file__)} */\n")
+    print(f"/ {{")
+    print(
+        f"\tthermistor_R25_{int(r25)}_B_{int(beta)}: thermistor-R25-{int(r25)}-B-{int(beta)} {{"
+    )
+    print(f'\t\tstatus = "disabled";')
+    print(f'\t\tcompatible = "zephyr,thermistor-rt-table";\n')
+
+    table = []
+    for temp in temps_range:
+        resistance = beta_equation_calc_resistance(r25, beta, temp)
+        table.append(f"<({int(temp)}) {int(resistance)}>")
+
+    tbl_string = ',\n\t\t\t'.join(table)
+    print(f"\t\t/* TR Table Format <temp resistance> */")
+    print(f"\t\ttr-table = {tbl_string};")
+    print(f"\t}};")
+    print(f"}};")
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser("NTC Thermistor generator", allow_abbrev=False)
+    parser.add_argument(
+        "-r25", type=float, required=True, help="Nominal resistance of thermistor"
+    )
+    parser.add_argument(
+        "-b", "--beta", type=float, required=True, help="Beta(25/85) value"
+    )
+    parser.add_argument(
+        "-i",
+        "--interval",
+        type=int,
+        required=False,
+        help="Generated table interval",
+        default=10,
+    )
+    parser.add_argument(
+        "-ti",
+        type=int,
+        required=False,
+        help="First temperature",
+        default=-25,
+    )
+    parser.add_argument(
+        "-tf",
+        type=int,
+        required=False,
+        help="Final temperature",
+        default=125,
+    )
+    args = parser.parse_args()
+
+    main(args.r25, args.beta, args.interval, args.ti, args.tf)