push script to generate NTC lut

fw/script/ntc_lut.py

@@ -0,0 +1,59 @@
+#!/usr/bin/env python3
+
+import math
+
+# Script to generate NTC lookup table
+#   ^ Vcc
+#   |
+# [RES]
+#   |
+#   +-- Vadc
+#   |
+# [NTC]
+#   |
+#  _|_ GND
+#  ///
+
+adc_res = 12
+ntc_value = 10_000 # at 25°C
+resistor_value = 10_000
+ntc_beta = 3380 # at 25°C
+steps = 64
+
+# NTC resistance to temperature (°C) conversion
+def resistance_to_t(ntc_r):
+	# Standard B-parameter equation
+    # T = 1 / (1/T0 + 1/B * ln(R/R0))
+	inv_t = 1/(25 + 273.15) + math.log(ntc_r/ntc_value)/ntc_beta
+	return 1/inv_t - 273.15
+
+# Resistor divider percentage to NTC resistance conversion
+# x = NTC / (NTC + RES)  => NTC = RES * x / (1 - x)
+def x_to_r(x):
+	x = max(0.0001, min(0.9999, x))
+	return resistor_value * x / (1 - x)
+
+# Use 4096 for cleaner divisions
+adc_max = 2**adc_res
+step_size = adc_max // steps
+
+values = []
+for i in range(steps):
+	adc_val = i * step_size
+	x = adc_val / adc_max
+	r = x_to_r(adc_val / adc_max)
+	t = resistance_to_t(r)
+	values.append(int(round(t)))
+
+def to_c_array(values, ctype="float", name="table", formatter=str, colcount=8):
+    # apply formatting to each element
+    values = [formatter(v) for v in values]
+    # split into rows with up to `colcount` elements per row
+    rows = [values[i:i+colcount] for i in range(0, len(values), colcount)]
+    # separate elements with commas, separate rows with newlines
+    body = ',\n    '.join([', '.join(r) for r in rows])
+    # assemble components into the complete string
+    return '{} {}[] = {{\n    {}}};'.format(ctype, name, body)
+
+print("uint8_t ntc_step_size = {};".format(int(step_size)))
+print(to_c_array(values, ctype="int16_t", name="ntc_lut", formatter=str, colcount=16))