Merge pull request #1319 from stv0g/Development
Cleanup and refactoring of termistor LUT generator (fixes bug #1305)
This commit is contained in:
Bo Herrmannsen
commit
5a5b95edbf
@ -1,12 +1,8 @@
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#!/usr/bin/python
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#!/usr/bin/python
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#
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# Creates a C code lookup table for doing ADC to temperature conversion
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# on a microcontroller
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# based on: http://hydraraptor.blogspot.com/2007/10/measuring-temperature-easy-way.html
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"""Thermistor Value Lookup Table Generator
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"""Thermistor Value Lookup Table Generator
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Generates lookup to temperature values for use in a microcontroller in C format based on:
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Generates lookup to temperature values for use in a microcontroller in C format based on:
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http://hydraraptor.blogspot.com/2007/10/measuring-temperature-easy-way.html
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http://en.wikipedia.org/wiki/Steinhart-Hart_equation
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The main use is for Arduino programs that read data from the circuit board described here:
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The main use is for Arduino programs that read data from the circuit board described here:
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http://make.rrrf.org/ts-1.0
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http://make.rrrf.org/ts-1.0
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@ -16,85 +12,87 @@ Usage: python createTemperatureLookup.py [options]
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Options:
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Options:
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-h, --help show this help
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-h, --help show this help
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--rp=... pull-up resistor
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--rp=... pull-up resistor
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--t1=ttt:rrr low temperature temperature:resistance point (around 25C)
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--t1=ttt:rrr low temperature temperature:resistance point (around 25 degC)
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--t2=ttt:rrr middle temperature temperature:resistance point (around 150C)
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--t2=ttt:rrr middle temperature temperature:resistance point (around 150 degC)
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--t3=ttt:rrr high temperature temperature:resistance point (around 250C)
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--t3=ttt:rrr high temperature temperature:resistance point (around 250 degC)
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--num-temps=... the number of temperature points to calculate (default: 20)
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--num-temps=... the number of temperature points to calculate (default: 36)
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"""
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"""
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from math import *
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from math import *
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import sys
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import sys
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import getopt
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import getopt
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"Constants"
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ZERO = 273.15 # zero point of Kelvin scale
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VADC = 5 # ADC voltage
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VCC = 5 # supply voltage
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ARES = 2**10 # 10 Bit ADC resolution
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VSTEP = VADC / ARES # ADC voltage resolution
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TMIN = 0 # lowest temperature in table
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TMAX = 350 # highest temperature in table
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class Thermistor:
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class Thermistor:
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"Class to do the thermistor maths"
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"Class to do the thermistor maths"
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def __init__(self, rp, t1, r1, t2, r2, t3, r3):
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def __init__(self, rp, t1, r1, t2, r2, t3, r3):
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t1 = t1 + 273.15 # low temperature (25C)
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l1 = log(r1)
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r1 = r1 # resistance at low temperature
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l2 = log(r2)
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t2 = t2 + 273.15 # middle temperature (150C)
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l3 = log(r3)
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r2 = r2 # resistance at middle temperature
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y1 = 1.0 / (t1 + ZERO) # adjust scale
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t3 = t3 + 273.15 # high temperature (250C)
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y2 = 1.0 / (t2 + ZERO)
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r3 = r3 # resistance at high temperature
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y3 = 1.0 / (t3 + ZERO)
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self.rp = rp # pull-up resistance
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x = (y2 - y1) / (l2 - l1)
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self.vadc = 5.0 # ADC reference
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y = (y3 - y1) / (l3 - l1)
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self.vcc = 5.0 # supply voltage to potential divider
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c = (y - x) / ((l3 - l2) * (l1 + l2 + l3))
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a1 = log(r1)
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b = x - c * (l1**2 + l2**2 + l1*l2)
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a2 = log(r2)
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a = y1 - (b + l1**2 *c)*l1
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a3 = log(r3)
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z = a1 - a2
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y = a1 - a3
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x = 1/t1 - 1/t2
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w = 1/t1 - 1/t3
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v = pow(a1,3) - pow(a2,3)
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u = pow(a1,3) - pow(a3,3)
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c3 = (x-z*w/y)/(v-z*u/y)
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c2 = (x-c3*v)/z
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c1 = 1/t1-c3*pow(a1,3)-c2*a1
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self.c1 = c1
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self.c2 = c2
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self.c3 = c3
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def res(self,adc):
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if c < 0:
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print "//////////////////////////////////////////////////////////////////////////////////////"
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print "// WARNING: negative coefficient 'c'! Something may be wrong with the measurements! //"
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print "//////////////////////////////////////////////////////////////////////////////////////"
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c = -c
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self.c1 = a # Steinhart-Hart coefficients
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self.c2 = b
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self.c3 = c
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self.rp = rp # pull-up resistance
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def resol(self, adc):
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"Convert ADC reading into a resolution"
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"Convert ADC reading into a resolution"
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res = self.temp(adc)-self.temp(adc+1)
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res = self.temp(adc)-self.temp(adc+1)
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return res
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return res
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def v(self,adc):
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def voltage(self, adc):
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"Convert ADC reading into a Voltage"
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"Convert ADC reading into a Voltage"
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v = adc * self.vadc / (1024 ) # convert the 10 bit ADC value to a voltage
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return adc * VSTEP # convert the 10 bit ADC value to a voltage
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return v
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def r(self,adc):
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def resist(self, adc):
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"Convert ADC reading into a resistance in Ohms"
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"Convert ADC reading into a resistance in Ohms"
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v = adc * self.vadc / (1024 ) # convert the 10 bit ADC value to a voltage
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r = self.rp * self.voltage(adc) / (VCC - self.voltage(adc)) # resistance of thermistor
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r = self.rp * v / (self.vcc - v) # resistance of thermistor
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return r
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return r
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def temp(self, adc):
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def temp(self, adc):
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"Convert ADC reading into a temperature in Celcius"
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"Convert ADC reading into a temperature in Celcius"
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v = adc * self.vadc / (1024 ) # convert the 10 bit ADC value to a voltage
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l = log(self.resist(adc))
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r = self.rp * v / (self.vcc - v) # resistance of thermistor
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Tinv = self.c1 + self.c2*l + self.c3* l**3) # inverse temperature
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lnr = log(r)
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return (1/Tinv) - ZERO # temperature
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Tinv = self.c1 + (self.c2*lnr) + (self.c3*pow(lnr,3))
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return (1/Tinv) - 273.15 # temperature
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def adc(self, temp):
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def adc(self, temp):
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"Convert temperature into a ADC reading"
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"Convert temperature into a ADC reading"
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y = (self.c1 - (1/(temp+273.15))) / (2*self.c3)
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x = (self.c1 - (1.0 / (temp+ZERO))) / (2*self.c3)
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x = sqrt(pow(self.c2 / (3*self.c3),3) + pow(y,2))
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y = sqrt((self.c2 / (3*self.c3)**3 + x**2)
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r = exp(pow(x-y,1.0/3) - pow(x+y,1.0/3)) # resistance of thermistor
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r = exp((y-x)**(1.0/3) - (y+x)**(1.0/3))
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return (r / (self.rp + r)) * (1024)
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return (r / (self.rp + r)) * ARES
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def main(argv):
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def main(argv):
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"Default values"
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rp = 4700;
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t1 = 25 # low temperature in Kelvin (25 degC)
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t1 = 25;
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r1 = 100000 # resistance at low temperature (10 kOhm)
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r1 = 100000;
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t2 = 150 # middle temperature in Kelvin (150 degC)
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t2 = 150;
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r2 = 1641.9 # resistance at middle temperature (1.6 KOhm)
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r2 = 1641.9;
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t3 = 250 # high temperature in Kelvin (250 degC)
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t3 = 250;
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r3 = 226.15 # resistance at high temperature (226.15 Ohm)
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r3 = 226.15;
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rp = 4700; # pull-up resistor (4.7 kOhm)
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num_temps = int(36);
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num_temps = 36; # number of entries for look-up table
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try:
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try:
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opts, args = getopt.getopt(argv, "h", ["help", "rp=", "t1=", "t2=", "t3=", "num-temps="])
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opts, args = getopt.getopt(argv, "h", ["help", "rp=", "t1=", "t2=", "t3=", "num-temps="])
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@ -124,29 +122,31 @@ def main(argv):
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elif opt == "--num-temps":
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elif opt == "--num-temps":
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num_temps = int(arg)
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num_temps = int(arg)
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max_adc = (1024 ) - 1
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min_temp = 0
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max_temp = 350
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increment = int(max_adc/(num_temps-1));
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t = Thermistor(rp, t1, r1, t2, r2, t3, r3)
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t = Thermistor(rp, t1, r1, t2, r2, t3, r3)
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tmp = (min_temp - max_temp) / (num_temps-1)
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increment = int((ARES-1)/(num_temps-1));
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print tmp
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step = (TMIN-TMAX) / (num_temps-1)
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temps = range(max_temp, min_temp + tmp, tmp);
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low_bound = t.temp(ARES-1);
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up_bound = t.temp(1);
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min_temp = int(TMIN if TMIN > low_bound else low_bound)
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max_temp = int(TMAX if TMAX < up_bound else up_bound)
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temps = range(max_temp, TMIN+step, step);
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print "// Thermistor lookup table for Marlin"
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print "// Thermistor lookup table for Marlin"
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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)
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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)
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print "// Steinhart-Hart Coefficients: %.15g, %.15g, %.15g " % (t.c1, t.c2, t.c3)
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print "// Steinhart-Hart Coefficients: a=%.15g, b=%.15g, c=%.15g " % (t.c1, t.c2, t.c3)
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print "//#define NUMTEMPS %s" % (len(temps))
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print "// Theoretical limits of termistor: %.2f to %.2f degC" % (low_bound, up_bound)
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print
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print "#define NUMTEMPS %s" % (len(temps))
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print "const short temptable[NUMTEMPS][2] PROGMEM = {"
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print "const short temptable[NUMTEMPS][2] PROGMEM = {"
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counter = 0
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for temp in temps:
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for temp in temps:
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counter = counter +1
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adc = t.adc(temp)
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if counter == len(temps):
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print " { (short) (%7.2f * OVERSAMPLENR ), %4s }%s // v=%.3f\tr=%.3f\tres=%.3f degC/count" % (adc , temp, \
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print " {(short)(%.2f*OVERSAMPLENR), %s} // v=%s r=%s res=%s C/count" % ((t.adc(temp)), temp, t.v(t.adc(temp)), t.r(t.adc(temp)),t.res(t.adc(temp)))
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',' if temp != temps[-1] else ' ', \
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else:
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t.voltage(adc), \
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print " {(short)(%.2f*OVERSAMPLENR), %s}, // v=%s r=%s res=%s C/count" % ((t.adc(temp)), temp, t.v(t.adc(temp)), t.r(t.adc(temp)),t.res(t.adc(temp)))
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t.resist( adc), \
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t.resol( adc) \
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)
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print "};"
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print "};"
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def usage():
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def usage():
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