#!/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

The main use is for Arduino programs that read data from the circuit board described here:
http://make.rrrf.org/ts-1.0

Usage: python createTemperatureLookup.py [options]

Options:
  -h, --help			show this help
  --r0=... 			thermistor rating where # is the ohm rating of the thermistor at t0 (eg: 10K = 10000)
  --t0=... 			thermistor temp rating where # is the temperature in Celsuis to get r0 (from your datasheet)
  --beta=...			thermistor beta rating. see http://reprap.org/bin/view/Main/MeasuringThermistorBeta
  --r1=...			R1 rating where # is the ohm rating of R1 (eg: 10K = 10000)
  --r2=... 			R2 rating where # is the ohm rating of R2 (eg: 10K = 10000)
  --num-temps=... 	the number of temperature points to calculate (default: 20)
"""

from math import *
import sys
import getopt

class Thermistor:
    "Class to do the thermistor maths"
    def __init__(self, r0, t0, beta, r1, r2):
        self.r0 = r0                        # stated resistance, e.g. 10K
        self.t0 = t0 + 273.15               # temperature at stated resistance, e.g. 25C
        self.beta = beta                    # stated beta, e.g. 3500
        self.vadc = 5.0                     # ADC reference
        self.vcc = 5.0                      # supply voltage to potential divider
        self.k = r0 * exp(-beta / self.t0)   # constant part of calculation

        if r1 > 0:
            self.vs = r1 * self.vcc / (r1 + r2) # effective bias voltage
            self.rs = r1 * r2 / (r1 + r2)       # effective bias impedance
        else:
            self.vs = self.vcc					 # effective bias voltage
            self.rs = r2                         # effective bias impedance

    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.rs * v / (self.vs - v)     # resistance of thermistor
        return (self.beta / log(r / self.k)) - 273.15        # temperature

    def setting(self, t):
        "Convert a temperature into a ADC value"
        r = self.r0 * exp(self.beta * (1 / (t + 273.15) - 1 / self.t0)) # resistance of the thermistor
        v = self.vs * r / (self.rs + r)     # the voltage at the potential divider
        return round(v / self.vadc * 1024)  # the ADC reading

def main(argv):

    r0 = 10000;
    t0 = 25;
    beta = 3947;
    r1 = 680;
    r2 = 1600;
    num_temps = int(20);
    
    try:
        opts, args = getopt.getopt(argv, "h", ["help", "r0=", "t0=", "beta=", "r1=", "r2="])
    except getopt.GetoptError:
        usage()
        sys.exit(2)
        
    for opt, arg in opts:
        if opt in ("-h", "--help"):
            usage()
            sys.exit()
        elif opt == "--r0":
            r0 = int(arg)
        elif opt == "--t0":
            t0 = int(arg)
        elif opt == "--beta":
         	beta = int(arg)
        elif opt == "--r1":
            r1 = int(arg)
        elif opt == "--r2":
            r2 = int(arg)

    if r1:
        max_adc = int(1023 * r1 / (r1 + r2));
    else:
        max_adc = 1023
            
    increment = int(max_adc/(num_temps-1));
    
    t = Thermistor(r0, t0, beta, r1, r2)

    adcs = range(1, max_adc, increment);
#	adcs = [1, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 130, 150, 190, 220,  250, 300]
    first = 1

    print "// Thermistor lookup table for RepRap Temperature Sensor Boards (http://make.rrrf.org/ts)"
    print "// Made with createTemperatureLookup.py (http://svn.reprap.org/trunk/reprap/firmware/Arduino/utilities/createTemperatureLookup.py)"
    print "// ./createTemperatureLookup.py --r0=%s --t0=%s --r1=%s --r2=%s --beta=%s --max-adc=%s" % (r0, t0, r1, r2, beta, max_adc)
    print "// r0: %s" % (r0)
    print "// t0: %s" % (t0)
    print "// r1: %s" % (r1)
    print "// r2: %s" % (r2)
    print "// beta: %s" % (beta)
    print "// max adc: %s" % (max_adc)
    print "#define NUMTEMPS %s" % (len(adcs))
    print "short temptable[NUMTEMPS][2] = {"

    counter = 0
    for adc in adcs:
        counter = counter +1
        if counter == len(adcs):
            print "   {%s, %s}" % (adc, int(t.temp(adc)))
        else:
            print "   {%s, %s}," % (adc, int(t.temp(adc)))
    print "};"
    
def usage():
    print __doc__

if __name__ == "__main__":
    main(sys.argv[1:])