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Adafruit_ADS1x15.py
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#!/usr/bin/python
import time
import smbus
from Adafruit_I2C import Adafruit_I2C
# ===========================================================================
# ADS1x15 Class
#
# Originally written by K. Townsend, Adafruit (https://github.com/adafruit/Adafruit-Raspberry-Pi-Python-Code/tree/master/Adafruit_ADS1x15)
# Updates and new functions implementation by Pedro Villanueva, 03/2013.
# The only error in the original code was in line 57:
# __ADS1015_REG_CONFIG_DR_920SPS = 0x0050
# should be
# __ADS1015_REG_CONFIG_DR_920SPS = 0x0060
#
# NOT IMPLEMENTED: Conversion ready pin, page 15 datasheet.
# ===========================================================================
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 = 0x0060 # 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 (also 0x00E0)
__ADS1115_REG_CONFIG_DR_8SPS = 0x0000 # 8 samples per second
__ADS1115_REG_CONFIG_DR_16SPS = 0x0020 # 16 samples per second
__ADS1115_REG_CONFIG_DR_32SPS = 0x0040 # 32 samples per second
__ADS1115_REG_CONFIG_DR_64SPS = 0x0060 # 64 samples per second
__ADS1115_REG_CONFIG_DR_128SPS = 0x0080 # 128 samples per second
__ADS1115_REG_CONFIG_DR_250SPS = 0x00A0 # 250 samples per second (default)
__ADS1115_REG_CONFIG_DR_475SPS = 0x00C0 # 475 samples per second
__ADS1115_REG_CONFIG_DR_860SPS = 0x00E0 # 860 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)
# Dictionaries with the sampling speed values
# These simplify and clean the code (avoid the abuse of if/elif/else clauses)
spsADS1115 = {
8:__ADS1115_REG_CONFIG_DR_8SPS,
16:__ADS1115_REG_CONFIG_DR_16SPS,
32:__ADS1115_REG_CONFIG_DR_32SPS,
64:__ADS1115_REG_CONFIG_DR_64SPS,
128:__ADS1115_REG_CONFIG_DR_128SPS,
250:__ADS1115_REG_CONFIG_DR_250SPS,
475:__ADS1115_REG_CONFIG_DR_475SPS,
860:__ADS1115_REG_CONFIG_DR_860SPS
}
spsADS1015 = {
128:__ADS1015_REG_CONFIG_DR_128SPS,
250:__ADS1015_REG_CONFIG_DR_250SPS,
490:__ADS1015_REG_CONFIG_DR_490SPS,
920:__ADS1015_REG_CONFIG_DR_920SPS,
1600:__ADS1015_REG_CONFIG_DR_1600SPS,
2400:__ADS1015_REG_CONFIG_DR_2400SPS,
3300:__ADS1015_REG_CONFIG_DR_3300SPS
}
# Dictionariy with the programable gains
pgaADS1x15 = {
6144:__ADS1015_REG_CONFIG_PGA_6_144V,
4096:__ADS1015_REG_CONFIG_PGA_4_096V,
2048:__ADS1015_REG_CONFIG_PGA_2_048V,
1024:__ADS1015_REG_CONFIG_PGA_1_024V,
512:__ADS1015_REG_CONFIG_PGA_0_512V,
256:__ADS1015_REG_CONFIG_PGA_0_256V
}
# Constructor
def __init__(self, address=0x48, ic=__IC_ADS1115, debug=False):
# Depending on if you have an old or a new Raspberry Pi, you
# may need to change the I2C bus. Older Pis use SMBus 0,
# whereas new Pis use SMBus 1. If you see an error like:
# 'Error accessing 0x48: Check your I2C address '
# change the SMBus number in the initializer below!
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 specfied: %h" % ic
return -1
else:
self.ic = ic
# Set pga value, so that getLastConversionResult() can use it,
# any function that accepts a pga value must update this.
self.pga = 6144
def readADCSingleEnded(self, channel=0, pga=6144, sps=250):
"Gets a single-ended ADC reading from the specified channel in mV. \
The sample rate for this mode (single-shot) can be used to lower the noise \
(low sps) or to lower the power consumption (high sps) by duty cycling, \
see datasheet page 14 for more info. \
The pga must be given in mV, see page 13 for the supported values."
# With invalid channel return -1
if (channel > 3):
if (self.debug):
print "ADS1x15: Invalid channel specified: %d" % channel
return -1
# Disable comparator, Non-latching, Alert/Rdy active low
# traditional comparator, single-shot mode
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_MODE_SINGLE
# Set sample per seconds, defaults to 250sps
# If sps is in the dictionary (defined in init) it returns the value of the constant
# othewise it returns the value for 250sps. This saves a lot of if/elif/else code!
if (self.ic == self.__IC_ADS1015):
config |= self.spsADS1015.setdefault(sps, self.__ADS1015_REG_CONFIG_DR_1600SPS)
else:
if ( (sps not in self.spsADS1115) & self.debug):
print "ADS1x15: Invalid pga specified: %d, using 6144mV" % sps
config |= self.spsADS1115.setdefault(sps, self.__ADS1115_REG_CONFIG_DR_250SPS)
# Set PGA/voltage range, defaults to +-6.144V
if ( (pga not in self.pgaADS1x15) & self.debug):
print "ADS1x15: Invalid pga specified: %d, using 6144mV" % sps
config |= self.pgaADS1x15.setdefault(pga, self.__ADS1015_REG_CONFIG_PGA_6_144V)
self.pga = pga
# Set the channel to be converted
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
# The minimum delay depends on the sps: delay >= 1/sps
# We add 0.1ms to be sure.
#
# Found that the following conversion check takes about 0.55 ms,
# so wait for the remainder of the expected conversion time (M.E. 2013)
delay = 1.0/sps-0.00055
time.sleep(delay)
# Make sure the conversion is finished
# If not, wait a little longer(M.E. 2013)
conversiondone = 0
while True:
conversiondone = self.i2c.readList(self.__ADS1015_REG_POINTER_CONFIG, 2)
conversiondone = (conversiondone[0] >> 7)
if conversiondone == 1:
break
# 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 and convert to mV
return ( ((result[0] << 8) | (result[1] & 0xFF)) >> 4 )*pga/2048.0
else:
# Return a mV value for the ADS1115
# (Take signed values into account as well)
val = (result[0] << 8) | (result[1])
if val > 0x7FFF:
return (val - 0xFFFF)*pga/32768.0
else:
return ( (result[0] << 8) | (result[1]) )*pga/32768.0
def readADCDifferential(self, chP=0, chN=1, pga=6144, sps=250):
"Gets a differential ADC reading from channels chP and chN in mV. \
The sample rate for this mode (single-shot) can be used to lower the noise \
(low sps) or to lower the power consumption (high sps) by duty cycling, \
see data sheet page 14 for more info. \
The pga must be given in mV, see page 13 for the supported values."
# Disable comparator, Non-latching, Alert/Rdy active low
# traditional comparator, single-shot mode
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_MODE_SINGLE
# Set channels
if ( (chP == 0) & (chN == 1) ):
config |= self.__ADS1015_REG_CONFIG_MUX_DIFF_0_1
elif ( (chP == 0) & (chN == 3) ):
config |= self.__ADS1015_REG_CONFIG_MUX_DIFF_0_3
elif ( (chP == 2) & (chN == 3) ):
config |= self.__ADS1015_REG_CONFIG_MUX_DIFF_2_3
elif ( (chP == 1) & (chN == 3) ):
config |= self.__ADS1015_REG_CONFIG_MUX_DIFF_1_3
else:
if (self.debug):
print "ADS1x15: Invalid channels specified: %d, %d" % (chP, chN)
return -1
# Set sample per seconds, defaults to 250sps
# If sps is in the dictionary (defined in init()) it returns the value of the constant
# othewise it returns the value for 250sps. This saves a lot of if/elif/else code!
if (self.ic == self.__IC_ADS1015):
config |= self.spsADS1015.setdefault(sps, self.__ADS1015_REG_CONFIG_DR_1600SPS)
else:
if ( (sps not in self.spsADS1115) & self.debug):
print "ADS1x15: Invalid pga specified: %d, using 6144mV" % sps
config |= self.spsADS1115.setdefault(sps, self.__ADS1115_REG_CONFIG_DR_250SPS)
# Set PGA/voltage range, defaults to +-6.144V
if ( (pga not in self.pgaADS1x15) & self.debug):
print "ADS1x15: Invalid pga specified: %d, using 6144mV" % sps
config |= self.pgaADS1x15.setdefault(pga, self.__ADS1015_REG_CONFIG_PGA_6_144V)
self.pga = pga
# 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
# The minimum delay depends on the sps: delay >= 1/sps
# We add 0.1ms to be sure
delay = 1.0/sps+0.0001
time.sleep(delay)
# 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 and convert to mV
return ( ((result[0] << 8) | (result[1] & 0xFF)) >> 4 )*pga/2048.0
else:
# Return a mV value for the ADS1115
# (Take signed values into account as well)
val = (result[0] << 8) | (result[1])
if val > 0x7FFF:
return (val - 0xFFFF)*pga/32768.0
else:
return ( (result[0] << 8) | (result[1]) )*pga/32768.0
def readADCDifferential01(self, pga=6144, sps=250):
"Gets a differential ADC reading from channels 0 and 1 in mV\
The sample rate for this mode (single-shot) can be used to lower the noise \
(low sps) or to lower the power consumption (high sps) by duty cycling, \
see data sheet page 14 for more info. \
The pga must be given in mV, see page 13 for the supported values."
return self.readADCDifferential(0, 1, pga, sps)
def readADCDifferential03(self, pga=6144, sps=250):
"Gets a differential ADC reading from channels 0 and 3 in mV \
The sample rate for this mode (single-shot) can be used to lower the noise \
(low sps) or to lower the power consumption (high sps) by duty cycling, \
see data sheet page 14 for more info. \
The pga must be given in mV, see page 13 for the supported values."
return self.readADCDifferential(0, 3, pga, sps)
def readADCDifferential13(self, pga=6144, sps=250):
"Gets a differential ADC reading from channels 1 and 3 in mV \
The sample rate for this mode (single-shot) can be used to lower the noise \
(low sps) or to lower the power consumption (high sps) by duty cycling, \
see data sheet page 14 for more info. \
The pga must be given in mV, see page 13 for the supported values."
return self.__readADCDifferential(1, 3, pga, sps)
def readADCDifferential23(self, pga=6144, sps=250):
"Gets a differential ADC reading from channels 2 and 3 in mV \
The sample rate for this mode (single-shot) can be used to lower the noise \
(low sps) or to lower the power consumption (high sps) by duty cycling, \
see data sheet page 14 for more info. \
The pga must be given in mV, see page 13 for the supported values."
return self.readADCDifferential(2, 3, pga, sps)
def startContinuousConversion(self, channel=0, pga=6144, sps=250):
"Starts the continuous conversion mode and returns the first ADC reading \
in mV from the specified channel. \
The sps controls the sample rate. \
The pga must be given in mV, see datasheet page 13 for the supported values. \
Use getLastConversionResults() to read the next values and \
stopContinuousConversion() to stop converting."
# 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
# Disable comparator, Non-latching, Alert/Rdy active low
# traditional comparator, continuous mode
# The last flag is the only change we need, page 11 datasheet
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_MODE_CONTIN
# Set sample per seconds, defaults to 250sps
# If sps is in the dictionary (defined in init()) it returns the value of the constant
# othewise it returns the value for 250sps. This saves a lot of if/elif/else code!
if (self.ic == self.__IC_ADS1015):
config |= self.spsADS1015.setdefault(sps, self.__ADS1015_REG_CONFIG_DR_1600SPS)
else:
if ( (sps not in self.spsADS1115) & self.debug):
print "ADS1x15: Invalid pga specified: %d, using 6144mV" % sps
config |= self.spsADS1115.setdefault(sps, self.__ADS1115_REG_CONFIG_DR_250SPS)
# Set PGA/voltage range, defaults to +-6.144V
if ( (pga not in self.pgaADS1x15) & self.debug):
print "ADS1x15: Invalid pga specified: %d, using 6144mV" % sps
config |= self.pgaADS1x15.setdefault(pga, self.__ADS1015_REG_CONFIG_PGA_6_144V)
self.pga = pga
# Set the channel to be converted
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 to begin conversions
# No need to change this for continuous mode!
config |= self.__ADS1015_REG_CONFIG_OS_SINGLE
# Write config register to the ADC
# Once we write the ADC will convert continously
# we can read the next values using getLastConversionResult
bytes = [(config >> 8) & 0xFF, config & 0xFF]
self.i2c.writeList(self.__ADS1015_REG_POINTER_CONFIG, bytes)
# Wait for the ADC conversion to complete
# The minimum delay depends on the sps: delay >= 1/sps
# We add 0.5ms to be sure
delay = 1.0/sps+0.0005
time.sleep(delay)
# 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 and convert to mV
return ( ((result[0] << 8) | (result[1] & 0xFF)) >> 4 )*pga/2048.0
else:
# Return a mV value for the ADS1115
# (Take signed values into account as well)
val = (result[0] << 8) | (result[1])
if val > 0x7FFF:
return (val - 0xFFFF)*pga/32768.0
else:
return ( (result[0] << 8) | (result[1]) )*pga/32768.0
def startContinuousDifferentialConversion(self, chP=0, chN=1, pga=6144, sps=250):
"Starts the continuous differential conversion mode and returns the first ADC reading \
in mV as the difference from the specified channels. \
The sps controls the sample rate. \
The pga must be given in mV, see datasheet page 13 for the supported values. \
Use getLastConversionResults() to read the next values and \
stopContinuousConversion() to stop converting."
# Disable comparator, Non-latching, Alert/Rdy active low
# traditional comparator, continuous mode
# The last flag is the only change we need, page 11 datasheet
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_MODE_CONTIN
# Set sample per seconds, defaults to 250sps
# If sps is in the dictionary (defined in init()) it returns the value of the constant
# othewise it returns the value for 250sps. This saves a lot of if/elif/else code!
if (self.ic == self.__IC_ADS1015):
config |= self.spsADS1015.setdefault(sps, self.__ADS1015_REG_CONFIG_DR_1600SPS)
else:
if ( (sps not in self.spsADS1115) & self.debug):
print "ADS1x15: Invalid pga specified: %d, using 6144mV" % sps
config |= self.spsADS1115.setdefault(sps, self.__ADS1115_REG_CONFIG_DR_250SPS)
# Set PGA/voltage range, defaults to +-6.144V
if ( (pga not in self.pgaADS1x15) & self.debug):
print "ADS1x15: Invalid pga specified: %d, using 6144mV" % sps
config |= self.pgaADS1x15.setdefault(pga, self.__ADS1015_REG_CONFIG_PGA_6_144V)
self.pga = pga
# Set channels
if ( (chP == 0) & (chN == 1) ):
config |= self.__ADS1015_REG_CONFIG_MUX_DIFF_0_1
elif ( (chP == 0) & (chN == 3) ):
config |= self.__ADS1015_REG_CONFIG_MUX_DIFF_0_3
elif ( (chP == 2) & (chN == 3) ):
config |= self.__ADS1015_REG_CONFIG_MUX_DIFF_2_3
elif ( (chP == 1) & (chN == 3) ):
config |= self.__ADS1015_REG_CONFIG_MUX_DIFF_1_3
else:
if (self.debug):
print "ADS1x15: Invalid channels specified: %d, %d" % (chP, chN)
return -1
# Set 'start single-conversion' bit to begin conversions
# No need to change this for continuous mode!
config |= self.__ADS1015_REG_CONFIG_OS_SINGLE
# Write config register to the ADC
# Once we write the ADC will convert continously
# we can read the next values using getLastConversionResult
bytes = [(config >> 8) & 0xFF, config & 0xFF]
self.i2c.writeList(self.__ADS1015_REG_POINTER_CONFIG, bytes)
# Wait for the ADC conversion to complete
# The minimum delay depends on the sps: delay >= 1/sps
# We add 0.5ms to be sure
delay = 1.0/sps+0.0005
time.sleep(delay)
# 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 and convert to mV
return ( ((result[0] << 8) | (result[1] & 0xFF)) >> 4 )*pga/2048.0
else:
# Return a mV value for the ADS1115
# (Take signed values into account as well)
val = (result[0] << 8) | (result[1])
if val > 0x7FFF:
return (val - 0xFFFF)*pga/32768.0
else:
return ( (result[0] << 8) | (result[1]) )*pga/32768.0
def stopContinuousConversion(self):
"Stops the ADC's conversions when in continuous mode \
and resets the configuration to its default value."
# Write the default config register to the ADC
# Once we write, the ADC will do a single conversion and
# enter power-off mode.
config = 0x8583 # Page 18 datasheet.
bytes = [(config >> 8) & 0xFF, config & 0xFF]
self.i2c.writeList(self.__ADS1015_REG_POINTER_CONFIG, bytes)
return True
def getLastConversionResults(self):
"Returns the last ADC conversion result in mV"
# 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 and convert to mV
return ( ((result[0] << 8) | (result[1] & 0xFF)) >> 4 )*self.pga/2048.0
else:
# Return a mV value for the ADS1115
# (Take signed values into account as well)
val = (result[0] << 8) | (result[1])
if val > 0x7FFF:
return (val - 0xFFFF)*self.pga/32768.0
else:
return ( (result[0] << 8) | (result[1]) )*self.pga/32768.0
def startSingleEndedComparator(self, channel, thresholdHigh, thresholdLow, \
pga=6144, sps=250, \
activeLow=True, traditionalMode=True, latching=False, \
numReadings=1):
"Starts the comparator mode on the specified channel, see datasheet pg. 15. \
In traditional mode it alerts (ALERT pin will go low) when voltage exceeds \
thresholdHigh until it falls below thresholdLow (both given in mV). \
In window mode (traditionalMode=False) it alerts when voltage doesn't lie\
between both thresholds.\
In latching mode the alert will continue until the conversion value is read. \
numReadings controls how many readings are necessary to trigger an alert: 1, 2 or 4.\
Use getLastConversionResults() to read the current value (which may differ \
from the one that triggered the alert) and clear the alert pin in latching mode. \
This function starts the continuous conversion mode. The sps controls \
the sample rate and the pga the gain, see datasheet page 13. "
# With invalid channel return -1
if (channel > 3):
if (self.debug):
print "ADS1x15: Invalid channel specified: %d" % channel
return -1
# Continuous mode
config = self.__ADS1015_REG_CONFIG_MODE_CONTIN
if (activeLow==False):
config |= self.__ADS1015_REG_CONFIG_CPOL_ACTVHI
else:
config |= self.__ADS1015_REG_CONFIG_CPOL_ACTVLOW
if (traditionalMode==False):
config |= self.__ADS1015_REG_CONFIG_CMODE_WINDOW
else:
config |= self.__ADS1015_REG_CONFIG_CMODE_TRAD
if (latching==True):
config |= self.__ADS1015_REG_CONFIG_CLAT_LATCH
else:
config |= self.__ADS1015_REG_CONFIG_CLAT_NONLAT
if (numReadings==4):
config |= self.__ADS1015_REG_CONFIG_CQUE_4CONV
elif (numReadings==2):
config |= self.__ADS1015_REG_CONFIG_CQUE_2CONV
else:
config |= self.__ADS1015_REG_CONFIG_CQUE_1CONV
# Set sample per seconds, defaults to 250sps
# If sps is in the dictionary (defined in init()) it returns the value of the constant
# othewise it returns the value for 250sps. This saves a lot of if/elif/else code!
if (self.ic == self.__IC_ADS1015):
if ( (sps not in self.spsADS1015) & self.debug):
print "ADS1x15: Invalid sps specified: %d, using 1600sps" % sps
config |= self.spsADS1015.setdefault(sps, self.__ADS1015_REG_CONFIG_DR_1600SPS)
else:
if ( (sps not in self.spsADS1115) & self.debug):
print "ADS1x15: Invalid sps specified: %d, using 250sps" % sps
config |= self.spsADS1115.setdefault(sps, self.__ADS1115_REG_CONFIG_DR_250SPS)
# Set PGA/voltage range, defaults to +-6.144V
if ( (pga not in self.pgaADS1x15) & self.debug):
print "ADS1x15: Invalid pga specified: %d, using 6144mV" % pga
config |= self.pgaADS1x15.setdefault(pga, self.__ADS1015_REG_CONFIG_PGA_6_144V)
self.pga = pga
# Set the channel to be converted
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 to begin conversions
config |= self.__ADS1015_REG_CONFIG_OS_SINGLE
# Write threshold high and low registers to the ADC
# V_digital = (2^(n-1)-1)/pga*V_analog
if (self.ic == self.__IC_ADS1015):
thresholdHighWORD = int(thresholdHigh*(2048.0/pga))
else:
thresholdHighWORD = int(thresholdHigh*(32767.0/pga))
bytes = [(thresholdHighWORD >> 8) & 0xFF, thresholdHighWORD & 0xFF]
self.i2c.writeList(self.__ADS1015_REG_POINTER_HITHRESH, bytes)
if (self.ic == self.__IC_ADS1015):
thresholdLowWORD = int(thresholdLow*(2048.0/pga))
else:
thresholdLowWORD = int(thresholdLow*(32767.0/pga))
bytes = [(thresholdLowWORD >> 8) & 0xFF, thresholdLowWORD & 0xFF]
self.i2c.writeList(self.__ADS1015_REG_POINTER_LOWTHRESH, bytes)
# Write config register to the ADC
# Once we write the ADC will convert continously and alert when things happen,
# we can read the converted values using getLastConversionResult
bytes = [(config >> 8) & 0xFF, config & 0xFF]
self.i2c.writeList(self.__ADS1015_REG_POINTER_CONFIG, bytes)
def startDifferentialComparator(self, chP, chN, thresholdHigh, thresholdLow, \
pga=6144, sps=250, \
activeLow=True, traditionalMode=True, latching=False, \
numReadings=1):
"Starts the comparator mode on the specified channel, see datasheet pg. 15. \
In traditional mode it alerts (ALERT pin will go low) when voltage exceeds \
thresholdHigh until it falls below thresholdLow (both given in mV). \
In window mode (traditionalMode=False) it alerts when voltage doesn't lie\
between both thresholds.\
In latching mode the alert will continue until the conversion value is read. \
numReadings controls how many readings are necessary to trigger an alert: 1, 2 or 4.\
Use getLastConversionResults() to read the current value (which may differ \
from the one that triggered the alert) and clear the alert pin in latching mode. \
This function starts the continuous conversion mode. The sps controls \
the sample rate and the pga the gain, see datasheet page 13. "
# Continuous mode
config = self.__ADS1015_REG_CONFIG_MODE_CONTIN
if (activeLow==False):
config |= self.__ADS1015_REG_CONFIG_CPOL_ACTVHI
else:
config |= self.__ADS1015_REG_CONFIG_CPOL_ACTVLOW
if (traditionalMode==False):
config |= self.__ADS1015_REG_CONFIG_CMODE_WINDOW
else:
config |= self.__ADS1015_REG_CONFIG_CMODE_TRAD
if (latching==True):
config |= self.__ADS1015_REG_CONFIG_CLAT_LATCH
else:
config |= self.__ADS1015_REG_CONFIG_CLAT_NONLAT
if (numReadings==4):
config |= self.__ADS1015_REG_CONFIG_CQUE_4CONV
elif (numReadings==2):
config |= self.__ADS1015_REG_CONFIG_CQUE_2CONV
else:
config |= self.__ADS1015_REG_CONFIG_CQUE_1CONV
# Set sample per seconds, defaults to 250sps
# If sps is in the dictionary (defined in init()) it returns the value of the constant
# othewise it returns the value for 250sps. This saves a lot of if/elif/else code!
if (self.ic == self.__IC_ADS1015):
if ( (sps not in self.spsADS1015) & self.debug):
print "ADS1x15: Invalid sps specified: %d, using 1600sps" % sps
config |= self.spsADS1015.setdefault(sps, self.__ADS1015_REG_CONFIG_DR_1600SPS)
else:
if ( (sps not in self.spsADS1115) & self.debug):
print "ADS1x15: Invalid sps specified: %d, using 250sps" % sps
config |= self.spsADS1115.setdefault(sps, self.__ADS1115_REG_CONFIG_DR_250SPS)
# Set PGA/voltage range, defaults to +-6.144V
if ( (pga not in self.pgaADS1x15) & self.debug):
print "ADS1x15: Invalid pga specified: %d, using 6144mV" % pga
config |= self.pgaADS1x15.setdefault(pga, self.__ADS1015_REG_CONFIG_PGA_6_144V)
self.pga = pga
# Set channels
if ( (chP == 0) & (chN == 1) ):
config |= self.__ADS1015_REG_CONFIG_MUX_DIFF_0_1
elif ( (chP == 0) & (chN == 3) ):
config |= self.__ADS1015_REG_CONFIG_MUX_DIFF_0_3
elif ( (chP == 2) & (chN == 3) ):
config |= self.__ADS1015_REG_CONFIG_MUX_DIFF_2_3
elif ( (chP == 1) & (chN == 3) ):
config |= self.__ADS1015_REG_CONFIG_MUX_DIFF_1_3
else:
if (self.debug):
print "ADS1x15: Invalid channels specified: %d, %d" % (chP, chN)
return -1
# Set 'start single-conversion' bit to begin conversions
config |= self.__ADS1015_REG_CONFIG_OS_SINGLE
# Write threshold high and low registers to the ADC
# V_digital = (2^(n-1)-1)/pga*V_analog
if (self.ic == self.__IC_ADS1015):
thresholdHighWORD = int(thresholdHigh*(2048.0/pga))
else:
thresholdHighWORD = int(thresholdHigh*(32767.0/pga))
bytes = [(thresholdHighWORD >> 8) & 0xFF, thresholdHighWORD & 0xFF]
self.i2c.writeList(self.__ADS1015_REG_POINTER_HITHRESH, bytes)
if (self.ic == self.__IC_ADS1015):
thresholdLowWORD = int(thresholdLow*(2048.0/pga))
else:
thresholdLowWORD = int(thresholdLow*(32767.0/pga))
bytes = [(thresholdLowWORD >> 8) & 0xFF, thresholdLowWORD & 0xFF]
self.i2c.writeList(self.__ADS1015_REG_POINTER_LOWTHRESH, bytes)
# Write config register to the ADC
# Once we write the ADC will convert continously and alert when things happen,
# we can read the converted values using getLastConversionResult
bytes = [(config >> 8) & 0xFF, config & 0xFF]
self.i2c.writeList(self.__ADS1015_REG_POINTER_CONFIG, bytes)