#!/bin/bash

#values in kiloohms to get rid of zeroes
VREF=3.3
#VREF=1.2

if [ "$1" == "-r" ]; then VREF=$2; shift;shift; fi
if [ "$1" == "-3" ]; then VREF=3.3; shift; fi
if [ "$1" == "-1" ]; then VREF=1.2; shift; fi

R1=$1
R2=$2
# if no second value, use insanely high, 100 megaohms
if [ "$R2" == "" ]; then R2=100000; fi


#3.3*33/(1/(1/100+1/100))
#
#            3.3v         rest
#             R2           R1
# OUT---*---/\/\/\---*---/\/\/\---GND
#       |            |
#        ---/\/\/\---*
#           Rtherm   |
#                    |
# REF----------------
# 

calcv()
{
  echo -n "$1'c/${2}kOhm: "
  # requires qalc (apt-get install qalc)
  RES=`qalc -t "$VREF*(1/(1/$2+1/$R2)+$R1)/(1/(1/$2+1/$R2))"`
  # compare with input voltage, truncate if higher
  if [ "`echo $RES|cut -d '.' -f 1`" -gt 11 ]; then echo "12   ($RES)";
    else echo $RES;
  fi
}

#uses tabulated data for the 100k thermistor
echo -n "Output voltages for Vref=${VREF}V, 100k thermistor, and R1=${R1}k"
if [ "$R2" != "100000" ]; then echo -n ", R2=${R2}k"; fi
echo
calcv 25 100
calcv 35 63
calcv 50 33
calcv 65 19
calcv 75 13
calcv 85 9