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Diffstat (limited to 'buildroot/share/scripts/createTemperatureLookupMarlin.py')
| -rw-r--r-- | buildroot/share/scripts/createTemperatureLookupMarlin.py | 158 |
1 files changed, 158 insertions, 0 deletions
diff --git a/buildroot/share/scripts/createTemperatureLookupMarlin.py b/buildroot/share/scripts/createTemperatureLookupMarlin.py new file mode 100644 index 0000000..b2d8964 --- /dev/null +++ b/buildroot/share/scripts/createTemperatureLookupMarlin.py @@ -0,0 +1,158 @@ +#!/usr/bin/env python +"""Thermistor Value Lookup Table Generator + +Generates lookup to temperature values for use in a microcontroller in C format based on: +https://en.wikipedia.org/wiki/Steinhart-Hart_equation + +The main use is for Arduino programs that read data from the circuit board described here: +https://reprap.org/wiki/Temperature_Sensor_v2.0 + +Usage: python createTemperatureLookupMarlin.py [options] + +Options: + -h, --help show this help + --rp=... pull-up resistor + --t1=ttt:rrr low temperature temperature:resistance point (around 25 degC) + --t2=ttt:rrr middle temperature temperature:resistance point (around 150 degC) + --t3=ttt:rrr high temperature temperature:resistance point (around 250 degC) + --num-temps=... the number of temperature points to calculate (default: 36) +""" + +from __future__ import print_function +from __future__ import division + +from math import * +import sys +import getopt + +"Constants" +ZERO = 273.15 # zero point of Kelvin scale +VADC = 5 # ADC voltage +VCC = 5 # supply voltage +ARES = pow(2,10) # 10 Bit ADC resolution +VSTEP = VADC / ARES # ADC voltage resolution +TMIN = 0 # lowest temperature in table +TMAX = 350 # highest temperature in table + +class Thermistor: + "Class to do the thermistor maths" + def __init__(self, rp, t1, r1, t2, r2, t3, r3): + l1 = log(r1) + l2 = log(r2) + l3 = log(r3) + y1 = 1.0 / (t1 + ZERO) # adjust scale + y2 = 1.0 / (t2 + ZERO) + y3 = 1.0 / (t3 + ZERO) + x = (y2 - y1) / (l2 - l1) + y = (y3 - y1) / (l3 - l1) + c = (y - x) / ((l3 - l2) * (l1 + l2 + l3)) + b = x - c * (l1**2 + l2**2 + l1*l2) + a = y1 - (b + l1**2 *c)*l1 + + if c < 0: + print("//////////////////////////////////////////////////////////////////////////////////////") + print("// WARNING: negative coefficient 'c'! Something may be wrong with the measurements! //") + print("//////////////////////////////////////////////////////////////////////////////////////") + c = -c + self.c1 = a # Steinhart-Hart coefficients + self.c2 = b + self.c3 = c + self.rp = rp # pull-up resistance + + def resol(self, adc): + "Convert ADC reading into a resolution" + res = self.temp(adc)-self.temp(adc+1) + return res + + def voltage(self, adc): + "Convert ADC reading into a Voltage" + return adc * VSTEP # convert the 10 bit ADC value to a voltage + + def resist(self, adc): + "Convert ADC reading into a resistance in Ohms" + r = self.rp * self.voltage(adc) / (VCC - self.voltage(adc)) # resistance of thermistor + return r + + def temp(self, adc): + "Convert ADC reading into a temperature in Celcius" + l = log(self.resist(adc)) + Tinv = self.c1 + self.c2*l + self.c3* l**3 # inverse temperature + return (1/Tinv) - ZERO # temperature + + def adc(self, temp): + "Convert temperature into a ADC reading" + x = (self.c1 - (1.0 / (temp+ZERO))) / (2*self.c3) + y = sqrt((self.c2 / (3*self.c3))**3 + x**2) + r = exp((y-x)**(1.0/3) - (y+x)**(1.0/3)) + return (r / (self.rp + r)) * ARES + +def main(argv): + "Default values" + t1 = 25 # low temperature in Kelvin (25 degC) + r1 = 100000 # resistance at low temperature (10 kOhm) + t2 = 150 # middle temperature in Kelvin (150 degC) + r2 = 1641.9 # resistance at middle temperature (1.6 KOhm) + t3 = 250 # high temperature in Kelvin (250 degC) + r3 = 226.15 # resistance at high temperature (226.15 Ohm) + rp = 4700; # pull-up resistor (4.7 kOhm) + num_temps = 36; # number of entries for look-up table + + try: + opts, args = getopt.getopt(argv, "h", ["help", "rp=", "t1=", "t2=", "t3=", "num-temps="]) + except getopt.GetoptError as err: + print(str(err)) + usage() + sys.exit(2) + + for opt, arg in opts: + if opt in ("-h", "--help"): + usage() + sys.exit() + elif opt == "--rp": + rp = int(arg) + elif opt == "--t1": + arg = arg.split(':') + t1 = float(arg[0]) + r1 = float(arg[1]) + elif opt == "--t2": + arg = arg.split(':') + t2 = float(arg[0]) + r2 = float(arg[1]) + elif opt == "--t3": + arg = arg.split(':') + t3 = float(arg[0]) + r3 = float(arg[1]) + elif opt == "--num-temps": + num_temps = int(arg) + + t = Thermistor(rp, t1, r1, t2, r2, t3, r3) + increment = int((ARES-1)/(num_temps-1)); + step = (TMIN-TMAX) / (num_temps-1) + low_bound = t.temp(ARES-1); + up_bound = t.temp(1); + min_temp = int(TMIN if TMIN > low_bound else low_bound) + max_temp = int(TMAX if TMAX < up_bound else up_bound) + temps = list(range(max_temp, TMIN+step, step)); + + print("// Thermistor lookup table for Marlin") + print("// ./createTemperatureLookupMarlin.py --rp=%s --t1=%s:%s --t2=%s:%s --t3=%s:%s --num-temps=%s" % (rp, t1, r1, t2, r2, t3, r3, num_temps)) + print("// Steinhart-Hart Coefficients: a=%.15g, b=%.15g, c=%.15g " % (t.c1, t.c2, t.c3)) + print("// Theoretical limits of thermistor: %.2f to %.2f degC" % (low_bound, up_bound)) + print() + print("const short temptable[][2] PROGMEM = {") + + for temp in temps: + adc = t.adc(temp) + print(" { OV(%7.2f), %4s }%s // v=%.3f\tr=%.3f\tres=%.3f degC/count" % (adc , temp, \ + ',' if temp != temps[-1] else ' ', \ + t.voltage(adc), \ + t.resist( adc), \ + t.resol( adc) \ + )) + print("};") + +def usage(): + print(__doc__) + +if __name__ == "__main__": + main(sys.argv[1:]) |