Monitor Analog Inputs

Analog Inputs

The four analog inputs are converted from analog to digital using an I2C device, MAX11601. This is an 8-bit A/D converter meaning that the analog input can be represented by a number from 0 to 255. The maximum signal of 16V is scaled down to a level that the A/D can read. So 16V should read 255. When converting from analog to digital, there are various errors that are introduced. Please refer to the datasheet for descriptions on possible errors.

Python Test Program

import smbus

import time

from os import system

bus=smbus.SMBus(1)

***** Analog Input Defines

MAX11600_ADDRESS = 0x64       #shifted left

MAX11600_CHANNEL0 = 0x00

MAX11600_CHANNEL1 = 0x02

MAX11600_CHANNEL2 = 0x04

MAX11600_CHANNEL3 = 0x06

MAX11600_SINGLE = 0x01

MAX11600_SCAN_SINGLE =0x60              

MAX11600_SETUP = 0x80

MAX11600_REF = 0x50

MAX11600_RST = 0x02

​

*** Function to initialize the MAX11601

def MAX11600_init():

                out = MAX11600_SETUP+MAX11600_REF+MAX11600_RST

                print "MAX11600 Setup:",hex(out)

                bus.write_byte(MAX11600_ADDRESS,out)

​

*** Function to read a channel

def MAX11600_read(channel):

                out = MAX11600_SCAN_SINGLE+channel+MAX11600_SINGLE

#             print "MAX11600-Conf:",hex(out)

                bus.write_byte(MAX11600_ADDRESS,out)

                return bus.read_byte(MAX11600_ADDRESS)

​

***** Initialize the devices

MAX11600_init()

while True:

                print ("Analog1:" MAX11600_read(MAX11600_CHANNEL0)

                time.sleep(1)

                print "Analog2",MAX11600_read(MAX11600_CHANNEL1)

                time.sleep(1)

                print "Analog3",MAX11600_read(MAX11600_CHANNEL2)

                time.sleep(1)

                print "Analog4",MAX11600_read(MAX11600_CHANNEL3)

                #_ = system('clear')

                time.sleep(1)