#!/usr/bin/env python
import time
import os
import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
#fonction lisant les donnees SPI de la puce MCP3008, parmi 8 entrees, de 0 a 7
def readadc(adcnum, clockpin, mosipin, misopin, cspin):
	    if ((adcnum > 7) or (adcnum < 0)):
			    return -1
	    GPIO.output(cspin, True)
	    GPIO.output(clockpin, False)  # start clock low
	    GPIO.output(cspin, False)	 # bring CS low

	    commandout = adcnum
	    commandout |= 0x18  # start bit + single-ended bit
	    commandout <<= 3    # we only need to send 5 bits here
	    for i in range(5):
			    if (commandout & 0x80):
					    GPIO.output(mosipin, True)
			    else:  
					    GPIO.output(mosipin, False)
			    commandout <<= 1
			    GPIO.output(clockpin, True)
			    GPIO.output(clockpin, False)

	    adcout = 0
	    # read in one empty bit, one null bit and 10 ADC bits
	    for i in range(12):
			    GPIO.output(clockpin, True)
			    GPIO.output(clockpin, False)
			    adcout <<= 1
			    if (GPIO.input(misopin)):
					    adcout |= 0x1

	    GPIO.output(cspin, True)
 
	    adcout /= 2	   # first bit is 'null' so drop it
	    return adcout

# ces numeros de pins GPIO doivent etre modifies pour correspondre aux broches utilisees.
SPICLK = 18
SPIMISO = 23
SPIMOSI = 24
SPICS = 25

# definition de l'interface SPI
GPIO.setup(SPIMOSI, GPIO.OUT)
GPIO.setup(SPIMISO, GPIO.IN)
GPIO.setup(SPICLK, GPIO.OUT)
GPIO.setup(SPICS, GPIO.OUT)

#definition du ADC utilise (broche du MCP3008)
adcnum = 0
while True:
# Lecture de la valeur brute du capteur
read_adc0 = readadc(adcnum, SPICLK, SPIMOSI, SPIMISO, SPICS)
# conversion de la valeur brute lue en milivolts = ADC * ( 3300 / 1024 )
millivolts = read_adc0 * ( 3300.0 / 1024.0)
bias=0;

# 10 mv per degree
temp_C = ((millivolts - 100.0) / 10.0) - 40.0+ bias
# convert celsius to fahrenheit
temp_F = ( temp_C * 9.0 / 5.0 ) + 32

print "valeurs lues : "
print "\tvaleur brute : %s" % read_adc0
print "\ttension : %s millivolts" % millivolts
print "\ttemperature : %s C" % temp_C
print "\ttemperature : %s F" % temp_F
time.sleep(1)