My Marlin configs for Fabrikator Mini and CTC i3 Pro B
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createTemperatureLookupMarlin.py 6.1KB

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  1. #!/usr/bin/env python
  2. """Thermistor Value Lookup Table Generator
  3. Generates lookup to temperature values for use in a microcontroller in C format based on:
  4. https://en.wikipedia.org/wiki/Steinhart-Hart_equation
  5. The main use is for Arduino programs that read data from the circuit board described here:
  6. https://reprap.org/wiki/Temperature_Sensor_v2.0
  7. Usage: python createTemperatureLookupMarlin.py [options]
  8. Options:
  9. -h, --help show this help
  10. --rp=... pull-up resistor
  11. --t1=ttt:rrr low temperature temperature:resistance point (around 25 degC)
  12. --t2=ttt:rrr middle temperature temperature:resistance point (around 150 degC)
  13. --t3=ttt:rrr high temperature temperature:resistance point (around 250 degC)
  14. --num-temps=... the number of temperature points to calculate (default: 36)
  15. """
  16. from __future__ import print_function
  17. from __future__ import division
  18. from math import *
  19. import sys,getopt
  20. "Constants"
  21. ZERO = 273.15 # zero point of Kelvin scale
  22. VADC = 5 # ADC voltage
  23. VCC = 5 # supply voltage
  24. ARES = pow(2,10) # 10 Bit ADC resolution
  25. VSTEP = VADC / ARES # ADC voltage resolution
  26. TMIN = 0 # lowest temperature in table
  27. TMAX = 350 # highest temperature in table
  28. class Thermistor:
  29. "Class to do the thermistor maths"
  30. def __init__(self, rp, t1, r1, t2, r2, t3, r3):
  31. l1 = log(r1)
  32. l2 = log(r2)
  33. l3 = log(r3)
  34. y1 = 1.0 / (t1 + ZERO) # adjust scale
  35. y2 = 1.0 / (t2 + ZERO)
  36. y3 = 1.0 / (t3 + ZERO)
  37. x = (y2 - y1) / (l2 - l1)
  38. y = (y3 - y1) / (l3 - l1)
  39. c = (y - x) / ((l3 - l2) * (l1 + l2 + l3))
  40. b = x - c * (l1**2 + l2**2 + l1*l2)
  41. a = y1 - (b + l1**2 *c)*l1
  42. if c < 0:
  43. print("//////////////////////////////////////////////////////////////////////////////////////")
  44. print("// WARNING: negative coefficient 'c'! Something may be wrong with the measurements! //")
  45. print("//////////////////////////////////////////////////////////////////////////////////////")
  46. c = -c
  47. self.c1 = a # Steinhart-Hart coefficients
  48. self.c2 = b
  49. self.c3 = c
  50. self.rp = rp # pull-up resistance
  51. def resol(self, adc):
  52. "Convert ADC reading into a resolution"
  53. res = self.temp(adc)-self.temp(adc+1)
  54. return res
  55. def voltage(self, adc):
  56. "Convert ADC reading into a Voltage"
  57. return adc * VSTEP # convert the 10 bit ADC value to a voltage
  58. def resist(self, adc):
  59. "Convert ADC reading into a resistance in Ohms"
  60. r = self.rp * self.voltage(adc) / (VCC - self.voltage(adc)) # resistance of thermistor
  61. return r
  62. def temp(self, adc):
  63. "Convert ADC reading into a temperature in Celsius"
  64. l = log(self.resist(adc))
  65. Tinv = self.c1 + self.c2*l + self.c3* l**3 # inverse temperature
  66. return (1/Tinv) - ZERO # temperature
  67. def adc(self, temp):
  68. "Convert temperature into a ADC reading"
  69. x = (self.c1 - (1.0 / (temp+ZERO))) / (2*self.c3)
  70. y = sqrt((self.c2 / (3*self.c3))**3 + x**2)
  71. r = exp((y-x)**(1.0/3) - (y+x)**(1.0/3))
  72. return (r / (self.rp + r)) * ARES
  73. def main(argv):
  74. "Default values"
  75. t1 = 25 # low temperature in Kelvin (25 degC)
  76. r1 = 100000 # resistance at low temperature (10 kOhm)
  77. t2 = 150 # middle temperature in Kelvin (150 degC)
  78. r2 = 1641.9 # resistance at middle temperature (1.6 KOhm)
  79. t3 = 250 # high temperature in Kelvin (250 degC)
  80. r3 = 226.15 # resistance at high temperature (226.15 Ohm)
  81. rp = 4700; # pull-up resistor (4.7 kOhm)
  82. num_temps = 36; # number of entries for look-up table
  83. try:
  84. opts, args = getopt.getopt(argv, "h", ["help", "rp=", "t1=", "t2=", "t3=", "num-temps="])
  85. except getopt.GetoptError as err:
  86. print(str(err))
  87. usage()
  88. sys.exit(2)
  89. for opt, arg in opts:
  90. if opt in ("-h", "--help"):
  91. usage()
  92. sys.exit()
  93. elif opt == "--rp":
  94. rp = int(arg)
  95. elif opt == "--t1":
  96. arg = arg.split(':')
  97. t1 = float(arg[0])
  98. r1 = float(arg[1])
  99. elif opt == "--t2":
  100. arg = arg.split(':')
  101. t2 = float(arg[0])
  102. r2 = float(arg[1])
  103. elif opt == "--t3":
  104. arg = arg.split(':')
  105. t3 = float(arg[0])
  106. r3 = float(arg[1])
  107. elif opt == "--num-temps":
  108. num_temps = int(arg)
  109. t = Thermistor(rp, t1, r1, t2, r2, t3, r3)
  110. increment = int((ARES-1)/(num_temps-1));
  111. step = (TMIN-TMAX) / (num_temps-1)
  112. low_bound = t.temp(ARES-1);
  113. up_bound = t.temp(1);
  114. min_temp = int(TMIN if TMIN > low_bound else low_bound)
  115. max_temp = int(TMAX if TMAX < up_bound else up_bound)
  116. temps = list(range(max_temp, TMIN+step, step));
  117. print("// Thermistor lookup table for Marlin")
  118. 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))
  119. print("// Steinhart-Hart Coefficients: a=%.15g, b=%.15g, c=%.15g " % (t.c1, t.c2, t.c3))
  120. print("// Theoretical limits of thermistor: %.2f to %.2f degC" % (low_bound, up_bound))
  121. print()
  122. print("const short temptable[][2] PROGMEM = {")
  123. for temp in temps:
  124. adc = t.adc(temp)
  125. print(" { OV(%7.2f), %4s }%s // v=%.3f\tr=%.3f\tres=%.3f degC/count" % (adc , temp, \
  126. ',' if temp != temps[-1] else ' ', \
  127. t.voltage(adc), \
  128. t.resist( adc), \
  129. t.resol( adc) \
  130. ))
  131. print("};")
  132. def usage():
  133. print(__doc__)
  134. if __name__ == "__main__":
  135. main(sys.argv[1:])