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Merge pull request #1319 from stv0g/Development

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Cleanup and refactoring of termistor LUT generator (fixes bug #1305)
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Bo Herrmannsen 2015-01-06 11:25:07 +01:00
commit 5a5b95edbf
2 changed files with 85 additions and 85 deletions
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Marlin/scripts/create_speed_lookuptable.py → Marlin/scripts/createSpeedLookupTable.py
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170
Marlin/scripts/createTemperatureLookupMarlin.py
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@ -1,12 +1,8 @@
#!/usr/bin/python
#
# Creates a C code lookup table for doing ADC to temperature conversion
# on a microcontroller
# based on: http://hydraraptor.blogspot.com/2007/10/measuring-temperature-easy-way.html
"""Thermistor Value Lookup Table Generator
Generates lookup to temperature values for use in a microcontroller in C format based on:
http://hydraraptor.blogspot.com/2007/10/measuring-temperature-easy-way.html
http://en.wikipedia.org/wiki/Steinhart-Hart_equation
The main use is for Arduino programs that read data from the circuit board described here:
http://make.rrrf.org/ts-1.0
@ -16,85 +12,87 @@ Usage: python createTemperatureLookup.py [options]
Options:
-h, --help show this help
--rp=... pull-up resistor
--t1=ttt:rrr low temperature temperature:resistance point (around 25C)
--t2=ttt:rrr middle temperature temperature:resistance point (around 150C)
--t3=ttt:rrr high temperature temperature:resistance point (around 250C)
--num-temps=... the number of temperature points to calculate (default: 20)
--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 math import *
import sys
import getopt
"Constants"
ZERO = 273.15 # zero point of Kelvin scale
VADC = 5 # ADC voltage
VCC = 5 # supply voltage
ARES = 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):
t1 = t1 + 273.15 # low temperature (25C)
r1 = r1 # resistance at low temperature
t2 = t2 + 273.15 # middle temperature (150C)
r2 = r2 # resistance at middle temperature
t3 = t3 + 273.15 # high temperature (250C)
r3 = r3 # resistance at high temperature
self.rp = rp # pull-up resistance
self.vadc = 5.0 # ADC reference
self.vcc = 5.0 # supply voltage to potential divider
a1 = log(r1)
a2 = log(r2)
a3 = log(r3)
z = a1 - a2
y = a1 - a3
x = 1/t1 - 1/t2
w = 1/t1 - 1/t3
v = pow(a1,3) - pow(a2,3)
u = pow(a1,3) - pow(a3,3)
c3 = (x-z*w/y)/(v-z*u/y)
c2 = (x-c3*v)/z
c1 = 1/t1-c3*pow(a1,3)-c2*a1
self.c1 = c1
self.c2 = c2
self.c3 = c3
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 res(self,adc):
def resol(self, adc):
"Convert ADC reading into a resolution"
res = self.temp(adc)-self.temp(adc+1)
return res
def v(self,adc):
def voltage(self, adc):
"Convert ADC reading into a Voltage"
v = adc * self.vadc / (1024 ) # convert the 10 bit ADC value to a voltage
return v
return adc * VSTEP # convert the 10 bit ADC value to a voltage
def r(self,adc):
def resist(self, adc):
"Convert ADC reading into a resistance in Ohms"
v = adc * self.vadc / (1024 ) # convert the 10 bit ADC value to a voltage
r = self.rp * v / (self.vcc - v) # resistance of thermistor
r = self.rp * self.voltage(adc) / (VCC - self.voltage(adc)) # resistance of thermistor
return r
def temp(self,adc):
def temp(self, adc):
"Convert ADC reading into a temperature in Celcius"
v = adc * self.vadc / (1024 ) # convert the 10 bit ADC value to a voltage
r = self.rp * v / (self.vcc - v) # resistance of thermistor
lnr = log(r)
Tinv = self.c1 + (self.c2*lnr) + (self.c3*pow(lnr,3))
return (1/Tinv) - 273.15 # temperature
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):
def adc(self, temp):
"Convert temperature into a ADC reading"
y = (self.c1 - (1/(temp+273.15))) / (2*self.c3)
x = sqrt(pow(self.c2 / (3*self.c3),3) + pow(y,2))
r = exp(pow(x-y,1.0/3) - pow(x+y,1.0/3)) # resistance of thermistor
return (r / (self.rp + r)) * (1024)
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):
rp = 4700;
t1 = 25;
r1 = 100000;
t2 = 150;
r2 = 1641.9;
t3 = 250;
r3 = 226.15;
num_temps = int(36);
"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="])
@ -102,7 +100,7 @@ def main(argv):
print str(err)
usage()
sys.exit(2)
for opt, arg in opts:
if opt in ("-h", "--help"):
usage()
@ -111,44 +109,46 @@ def main(argv):
rp = int(arg)
elif opt == "--t1":
arg = arg.split(':')
t1 = float( arg[0])
r1 = float( arg[1])
t1 = float(arg[0])
r1 = float(arg[1])
elif opt == "--t2":
arg = arg.split(':')
t2 = float( arg[0])
r2 = float( arg[1])
t2 = float(arg[0])
r2 = float(arg[1])
elif opt == "--t3":
arg = arg.split(':')
t3 = float( arg[0])
r3 = float( arg[1])
t3 = float(arg[0])
r3 = float(arg[1])
elif opt == "--num-temps":
num_temps = int(arg)
num_temps = int(arg)
max_adc = (1024 ) - 1
min_temp = 0
max_temp = 350
increment = int(max_adc/(num_temps-1));
t = Thermistor(rp, t1, r1, t2, r2, t3, r3)
tmp = (min_temp - max_temp) / (num_temps-1)
print tmp
temps = range(max_temp, min_temp + tmp, tmp);
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 = 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: %.15g, %.15g, %.15g " % (t.c1, t.c2, t.c3)
print "//#define NUMTEMPS %s" % (len(temps))
print "// Steinhart-Hart Coefficients: a=%.15g, b=%.15g, c=%.15g " % (t.c1, t.c2, t.c3)
print "// Theoretical limits of termistor: %.2f to %.2f degC" % (low_bound, up_bound)
print
print "#define NUMTEMPS %s" % (len(temps))
print "const short temptable[NUMTEMPS][2] PROGMEM = {"
counter = 0
for temp in temps:
counter = counter +1
if counter == len(temps):
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)))
else:
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)))
adc = t.adc(temp)
print " { (short) (%7.2f * OVERSAMPLENR ), %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__