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Adafruit_ADS1x15.py
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#!/usr/bin/python
import time
from Adafruit_I2C import Adafruit_I2C
# ===========================================================================
# ADS1x15 Class
# ===========================================================================
class ADS1x15:
i2c = None
# IC Identifiers
__IC_ADS1015 = 0x00
__IC_ADS1115 = 0x01
# Pointer Register
__ADS1015_REG_POINTER_MASK = 0x03
__ADS1015_REG_POINTER_CONVERT = 0x00
__ADS1015_REG_POINTER_CONFIG = 0x01
__ADS1015_REG_POINTER_LOWTHRESH = 0x02
__ADS1015_REG_POINTER_HITHRESH = 0x03
# Config Register
__ADS1015_REG_CONFIG_OS_MASK = 0x8000
__ADS1015_REG_CONFIG_OS_SINGLE = 0x8000 # Write: Set to start a single-conversion
__ADS1015_REG_CONFIG_OS_BUSY = 0x0000 # Read: Bit = 0 when conversion is in progress
__ADS1015_REG_CONFIG_OS_NOTBUSY = 0x8000 # Read: Bit = 1 when device is not performing a conversion
__ADS1015_REG_CONFIG_MUX_MASK = 0x7000
__ADS1015_REG_CONFIG_MUX_DIFF_0_1 = 0x0000 # Differential P = AIN0, N = AIN1 (default)
__ADS1015_REG_CONFIG_MUX_DIFF_0_3 = 0x1000 # Differential P = AIN0, N = AIN3
__ADS1015_REG_CONFIG_MUX_DIFF_1_3 = 0x2000 # Differential P = AIN1, N = AIN3
__ADS1015_REG_CONFIG_MUX_DIFF_2_3 = 0x3000 # Differential P = AIN2, N = AIN3
__ADS1015_REG_CONFIG_MUX_SINGLE_0 = 0x4000 # Single-ended AIN0
__ADS1015_REG_CONFIG_MUX_SINGLE_1 = 0x5000 # Single-ended AIN1
__ADS1015_REG_CONFIG_MUX_SINGLE_2 = 0x6000 # Single-ended AIN2
__ADS1015_REG_CONFIG_MUX_SINGLE_3 = 0x7000 # Single-ended AIN3
__ADS1015_REG_CONFIG_PGA_MASK = 0x0E00
__ADS1015_REG_CONFIG_PGA_6_144V = 0x0000 # +/-6.144V range
__ADS1015_REG_CONFIG_PGA_4_096V = 0x0200 # +/-4.096V range
__ADS1015_REG_CONFIG_PGA_2_048V = 0x0400 # +/-2.048V range (default)
__ADS1015_REG_CONFIG_PGA_1_024V = 0x0600 # +/-1.024V range
__ADS1015_REG_CONFIG_PGA_0_512V = 0x0800 # +/-0.512V range
__ADS1015_REG_CONFIG_PGA_0_256V = 0x0A00 # +/-0.256V range
__ADS1015_REG_CONFIG_MODE_MASK = 0x0100
__ADS1015_REG_CONFIG_MODE_CONTIN = 0x0000 # Continuous conversion mode
__ADS1015_REG_CONFIG_MODE_SINGLE = 0x0100 # Power-down single-shot mode (default)
__ADS1015_REG_CONFIG_DR_MASK = 0x00E0
__ADS1015_REG_CONFIG_DR_128SPS = 0x0000 # 128 samples per second
__ADS1015_REG_CONFIG_DR_250SPS = 0x0020 # 250 samples per second
__ADS1015_REG_CONFIG_DR_490SPS = 0x0040 # 490 samples per second
__ADS1015_REG_CONFIG_DR_920SPS = 0x0050 # 920 samples per second
__ADS1015_REG_CONFIG_DR_1600SPS = 0x0080 # 1600 samples per second (default)
__ADS1015_REG_CONFIG_DR_2400SPS = 0x00A0 # 2400 samples per second
__ADS1015_REG_CONFIG_DR_3300SPS = 0x00C0 # 3300 samples per second
__ADS1015_REG_CONFIG_CMODE_MASK = 0x0010
__ADS1015_REG_CONFIG_CMODE_TRAD = 0x0000 # Traditional comparator with hysteresis (default)
__ADS1015_REG_CONFIG_CMODE_WINDOW = 0x0010 # Window comparator
__ADS1015_REG_CONFIG_CPOL_MASK = 0x0008
__ADS1015_REG_CONFIG_CPOL_ACTVLOW = 0x0000 # ALERT/RDY pin is low when active (default)
__ADS1015_REG_CONFIG_CPOL_ACTVHI = 0x0008 # ALERT/RDY pin is high when active
__ADS1015_REG_CONFIG_CLAT_MASK = 0x0004 # Determines if ALERT/RDY pin latches once asserted
__ADS1015_REG_CONFIG_CLAT_NONLAT = 0x0000 # Non-latching comparator (default)
__ADS1015_REG_CONFIG_CLAT_LATCH = 0x0004 # Latching comparator
__ADS1015_REG_CONFIG_CQUE_MASK = 0x0003
__ADS1015_REG_CONFIG_CQUE_1CONV = 0x0000 # Assert ALERT/RDY after one conversions
__ADS1015_REG_CONFIG_CQUE_2CONV = 0x0001 # Assert ALERT/RDY after two conversions
__ADS1015_REG_CONFIG_CQUE_4CONV = 0x0002 # Assert ALERT/RDY after four conversions
__ADS1015_REG_CONFIG_CQUE_NONE = 0x0003 # Disable the comparator and put ALERT/RDY in high state (default)
# Constructor
def __init__(self, address=0x48, ic=__IC_ADS1015, debug=False):
self.i2c = Adafruit_I2C(address)
self.address = address
self.debug = debug
# Make sure the IC specified is valid
if ((ic < self.__IC_ADS1015) | (ic > self.__IC_ADS1115)):
if (self.debug):
print "ADS1x15: Invalid IC. Using the ADS1015 by default"
self.ic = __IC_ADS1015
else:
self.ic = ic
def readADCSingleEnded(self, channel=0):
"Gets a single-ended ADC reading from the specified channel (1 bit = 3mV)"
# Default to channel 0 with invalid channel, or return -1?
if (channel > 3):
if (self.debug):
print "ADS1x15: Invalid channel specified: %d" % channel
return -1
# Start with default values
config = self.__ADS1015_REG_CONFIG_CQUE_NONE | \
self.__ADS1015_REG_CONFIG_CLAT_NONLAT | \
self.__ADS1015_REG_CONFIG_CPOL_ACTVLOW | \
self.__ADS1015_REG_CONFIG_CMODE_TRAD | \
self.__ADS1015_REG_CONFIG_DR_1600SPS | \
self.__ADS1015_REG_CONFIG_MODE_SINGLE
# Set PGA/voltage range (1 bit = 3mV using the default range)
config |= self.__ADS1015_REG_CONFIG_PGA_6_144V # +/- 6.144V range
if channel == 3:
config |= self.__ADS1015_REG_CONFIG_MUX_SINGLE_3
elif channel == 2:
config |= self.__ADS1015_REG_CONFIG_MUX_SINGLE_2
elif channel == 1:
config |= self.__ADS1015_REG_CONFIG_MUX_SINGLE_1
else:
config |= self.__ADS1015_REG_CONFIG_MUX_SINGLE_0
# Set 'start single-conversion' bit
config |= self.__ADS1015_REG_CONFIG_OS_SINGLE
# Write config register to the ADC
bytes = [(config >> 8) & 0xFF, config & 0xFF]
self.i2c.writeList(self.__ADS1015_REG_POINTER_CONFIG, bytes)
# Wait for the ADC conversion to complete
time.sleep(0.001)
# Read the conversion results
result = self.i2c.readList(self.__ADS1015_REG_POINTER_CONVERT, 2)
if (self.ic == self.__IC_ADS1015):
# Shift right 4 bits for the 12-bit ADS1015
return ( ((result[0] << 8) | (result[1] & 0xFF)) >> 4 )
else:
# Return 16-bit value for the ADS1115
return ( (result[0] << 8) | (result[1] & 0xFF) )
def readADCDifferential01(self):
"Gets a differential ADC reading from channels 0 and 1"
def readADCDifferential23(self):
"Gets a differential ADC reading from channels 2 and 3"
def startSingleEndedComparator(self, channel, threshold):
"Starts the comparator in single-ended mode on the specified channel"
def getLastConversionResults(self):
"Returns the last ADC conversion result"