#!/usr/bin/python
#
# analogmux.py
#
# Mar.21/2015: v1.00 released
#
# MCP3208 and 74HC138N data acquisition library with SPI multiplexer
# for the Raspberry Pi. Please see URL below for the introductory article.
#
# http://www.mikronauts.com/raspberry-pi/raspberry-pi-analog-to-digital-conversion-experiments-and-howto
#
# Copyright 2015 William Henning
# http://Mikronauts.com
#
# supports up to eight MCP3208 12 bit analog to digital converters for up to 64 analog inputs
#
# tested with three MCP3208's
#
# should also work with MCP3008 with a modified readadc()
#

import RPi.GPIO as GPIO
import spidev
import time

# module constants for the GPIO channels

A2 = 25
A1 = 24
A0 = 23

# make a list of requests to spead up readadc
req=[[6,0,0], [6,64,0],[6,128,0],[6,192,0],[7,0,0], [7,64,0],[7,128,0],[7,192,0]]

# list is based on 'r = spi.xfer2([6|(adcnum>>2),(adcnum&3)<<6,0])' which in turn was based on readadc12 from
# http://git.agocontrol.com/apagg/agocontrol-work/blob/93f7d9051aebf79c794e3d5fa4feea92c9221831/raspiMCP3xxxGPIO/MCP3208.py

# choose the current SPI device (one of eight)
def spi_device(devno):
    GPIO.output(A2,(devno >> 2)&1)
    GPIO.output(A1,(devno >> 1)&1)
    GPIO.output(A0,devno & 1)

# read SPI data from MCP3008 chip, 8 possible adc's (0 thru 7)
def readadc(adcnum):
    r = spi.xfer2(req[adcnum])
    return ((r[1]&15)<<8) + r[2]

# set up the demultiplexer
GPIO.setmode(GPIO.BCM)
GPIO.setup(A2, GPIO.OUT)
GPIO.setup(A1, GPIO.OUT)
GPIO.setup(A0, GPIO.OUT)

spi = spidev.SpiDev()

spi.open(0,1)   # port=0, CS=1

spi.max_speed_hz=1953000  # any faster and we lose ADC resolution

count = 1

while 1:

    print "--------------------------"
    print "SPI DEVICE", n, "SCAN ", count

    spi_device(1)
    mul=0.002

    csv = time.asctime()  # start each csv line with a time stamp

    for chan in range(0,8):
        x = readadc(chan)
        csv = csv + "," + str(x*mul)
        print chan, x*mul

    csv = csv + "\n"

    f = open("csv.txt","a")
    f.write(csv)
    f.close()
    
    time.sleep(15)
    count = count + 1