createTemperatureLookupMarlin Namespace Reference

Classes
class	Thermistor

Functions
def	main (argv)
def	usage ()

Variables
float	ZERO = 273.15
int	VADC = 5
int	VCC = 5
	ARES = pow(2,10)
int	VSTEP = VADC / ARES
int	TMIN = 0
int	TMAX = 350

Detailed Description

Thermistor Value Lookup Table Generator

Generates lookup to temperature values for use in a microcontroller in C format based on:
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://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)

Function Documentation

main()

def createTemperatureLookupMarlin.main

(

argv

)

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("};")
 

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usage()

def createTemperatureLookupMarlin.usage

(

)

def usage():
    print(__doc__)
 

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Variable Documentation

ZERO

float createTemperatureLookupMarlin.ZERO = 273.15

VADC

int createTemperatureLookupMarlin.VADC = 5

VCC

int createTemperatureLookupMarlin.VCC = 5

ARES

createTemperatureLookupMarlin.ARES = pow(2,10)

VSTEP

int createTemperatureLookupMarlin.VSTEP = VADC / ARES

TMIN

int createTemperatureLookupMarlin.TMIN = 0

TMAX

int createTemperatureLookupMarlin.TMAX = 350