sgh_explorer_analog.py

import time

adc_available = True

try:
    from smbus import SMBus
except ImportError:
    exit("This library requires python-smbus\nInstall with: sudo apt-get install python-smbus")

def i2c_bus_id():
    revision = ([l[12:-1] for l in open('/proc/cpuinfo','r').readlines() if l[:8]=="Revision"]+['0000'])[0]
    return 1 if int(revision, 16) >= 4 else 0

address = 0x48
i2c = SMBus(i2c_bus_id())

REG_CONV = 0x00
REG_CFG = 0x01

samples_per_second_map = {128: 0x0000, 250: 0x0020, 490: 0x0040, 920: 0x0060, 1600: 0x0080, 2400: 0x00A0, 3300: 0x00C0}
channel_map = {0: 0x4000, 1: 0x5000, 2: 0x6000, 3: 0x7000}
programmable_gain_map = {6144: 0x0000, 4096: 0x0200, 2048: 0x0400, 1024: 0x0600, 512: 0x0800, 256: 0x0A00}

PGA_6_144V = 6144
PGA_4_096V = 4096
PGA_2_048V = 2048
PGA_1_024V = 1024
PGA_0_512V = 512
PGA_0_256V = 256

class ADS1015():

    def read_se_adc(self,channel=1, programmable_gain=PGA_6_144V, samples_per_second=1600):
        # sane defaults
        config = 0x0003 | 0x0100

        config |= samples_per_second_map[samples_per_second]
        config |= channel_map[channel]
        config |= programmable_gain_map[programmable_gain]

        # set "single shot" mode
        config |= 0x8000

        # write single conversion flag
        i2c.write_i2c_block_data(address, REG_CFG, [(config >> 8) & 0xFF, config & 0xFF])

        delay = (1.0 / samples_per_second) + 0.0001
        time.sleep(delay)

        data = i2c.read_i2c_block_data(address, REG_CONV)

        return (((data[0] << 8) | data[1]) >> 4 ) * programmable_gain / 2048.0 / 1000.0
'''
ADS = ADS1015()

try:
    for loop in range(0,4):
        print loop, ADS.read_se_adc(loop)
except IOError:
    adc_available = False
'''