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Pycom class for interacting with the ADS1115 ADC
import ustruct
import time
_REGISTER_MASK = const(0x03)
_REGISTER_CONVERT = const(0x00)
_REGISTER_CONFIG = const(0x01)
_REGISTER_LOWTHRESH = const(0x02)
_REGISTER_HITHRESH = const(0x03)
_OS_MASK = const(0x8000)
_OS_SINGLE = const(0x8000) # Write: Set to start a single-conversion
_OS_BUSY = const(0x0000) # Read: Bit=0 when conversion is in progress
_OS_NOTBUSY = const(0x8000) # Read: Bit=1 when device is not performing a conversion
_MUX_MASK = const(0x7000)
_MUX_DIFF_0_1 = const(0x0000) # Differential P = AIN0, N = AIN1 (default)
_MUX_DIFF_0_3 = const(0x1000) # Differential P = AIN0, N = AIN3
_MUX_DIFF_1_3 = const(0x2000) # Differential P = AIN1, N = AIN3
_MUX_DIFF_2_3 = const(0x3000) # Differential P = AIN2, N = AIN3
_MUX_SINGLE_0 = const(0x4000) # Single-ended AIN0
_MUX_SINGLE_1 = const(0x5000) # Single-ended AIN1
_MUX_SINGLE_2 = const(0x6000) # Single-ended AIN2
_MUX_SINGLE_3 = const(0x7000) # Single-ended AIN3
_PGA_MASK = const(0x0E00)
PGA_6_144V = const(0x0000) # +/-6.144V range = Gain 2/3
PGA_4_096V = const(0x0200) # +/-4.096V range = Gain 1
PGA_2_048V = const(0x0400) # +/-2.048V range = Gain 2 (default)
PGA_1_024V = const(0x0600) # +/-1.024V range = Gain 4
PGA_0_512V = const(0x0800) # +/-0.512V range = Gain 8
PGA_0_256V = const(0x0A00) # +/-0.256V range = Gain 16
_MODE_MASK = const(0x0100)
_MODE_CONTIN = const(0x0000) # Continuous conversion mode
_MODE_SINGLE = const(0x0100) # Power-down single-shot mode (default)
_DR_MASK = const(0x00E0)
_DR_128SPS = const(0x0000) # 128 samples per second
_DR_250SPS = const(0x0020) # 250 samples per second
_DR_490SPS = const(0x0040) # 490 samples per second
_DR_920SPS = const(0x0060) # 920 samples per second
_DR_1600SPS = const(0x0080) # 1600 samples per second (default)
_DR_2400SPS = const(0x00A0) # 2400 samples per second
_DR_3300SPS = const(0x00C0) # 3300 samples per second
_CMODE_MASK = const(0x0010)
_CMODE_TRAD = const(0x0000) # Traditional comparator with hysteresis (default)
_CMODE_WINDOW = const(0x0010) # Window comparator
_CPOL_MASK = const(0x0008)
_CPOL_ACTVLOW = const(0x0000) # ALERT/RDY pin is low when active (default)
_CPOL_ACTVHI = const(0x0008) # ALERT/RDY pin is high when active
_CLAT_MASK = const(0x0004) # Determines if ALERT/RDY pin latches once asserted
_CLAT_NONLAT = const(0x0000) # Non-latching comparator (default)
_CLAT_LATCH = const(0x0004) # Latching comparator
_CQUE_MASK = const(0x0003)
_CQUE_1CONV = const(0x0000) # Assert ALERT/RDY after one conversions
_CQUE_2CONV = const(0x0001) # Assert ALERT/RDY after two conversions
_CQUE_4CONV = const(0x0002) # Assert ALERT/RDY after four conversions
_CQUE_NONE = const(0x0003) # Disable the comparator and put ALERT/RDY in high state (default)
# A mapping of gain values to rail to rail voltage range
_GAINS = {
PGA_6_144V: 12.288, # 2/3x
PGA_4_096V: 8.192, # 1x
PGA_2_048V: 4.096, # 2x
PGA_1_024V: 2.048, # 4x
PGA_0_512V: 1.024, # 8x
PGA_0_256V: 0.512 # 16x
}
_CHANNELS = (_MUX_SINGLE_0, _MUX_SINGLE_1, _MUX_SINGLE_2, _MUX_SINGLE_3)
_DIFFS = {
(0, 1): _MUX_DIFF_0_1,
(0, 3): _MUX_DIFF_0_3,
(1, 3): _MUX_DIFF_1_3,
(2, 3): _MUX_DIFF_2_3,
}
class ADS1115:
def __init__(self, i2c, address=0x48, gain=PGA_4_096V):
self.i2c = i2c
self.address = address
if gain in _GAINS:
self.gain = gain
else:
raise ValueError('gain must be one of the values in _GAINS')
def _write_register(self, register, value):
data = ustruct.pack('>BH', register, value)
self.i2c.writeto(self.address, data)
def _read_register(self, register):
data = self.i2c.readfrom_mem(self.address, register, 2 )
return ustruct.unpack('>h', data)[0]
def read_config(self):
return self.i2c.readfrom_mem(self.address, 1, 2)
def get_voltage(self, channel):
return _GAINS[self.gain] * (self.read(channel) / 65535)
def read(self, channel):
self._write_register(_REGISTER_CONFIG, _CQUE_NONE | _CLAT_NONLAT |
_CPOL_ACTVLOW | _CMODE_TRAD | _DR_1600SPS | _MODE_SINGLE |
_OS_SINGLE | self.gain | _CHANNELS[channel])
while not self._read_register(_REGISTER_CONFIG) & _OS_NOTBUSY:
time.sleep_ms(1)
return self._read_register(_REGISTER_CONVERT)
def diff(self, channel1, channel2):
self._write_register(_REGISTER_CONFIG, _CQUE_NONE | _CLAT_NONLAT |
_CPOL_ACTVLOW | _CMODE_TRAD | _DR_1600SPS | _MODE_SINGLE |
_OS_SINGLE | self.gain | _DIFFS[(channel1, channel2)])
while not self._read_register(_REGISTER_CONFIG) & _OS_NOTBUSY:
time.sleep_ms(1)
return self._read_register(_REGISTER_CONVERT)
def alert_start(self, channel, threshold):
self._write_register(_REGISTER_HITHRESH, threshold)
self._write_register(_REGISTER_CONFIG, _CQUE_1CONV | _CLAT_LATCH |
_CPOL_ACTVLOW | _CMODE_TRAD | _DR_1600SPS | _MODE_CONTIN |
_MODE_CONTIN | self.gain | _CHANNELS[channel])
def alert_read(self):
return self._read_register(_REGISTER_CONVERT)
'''
This example assumes you have set the ADS1115 address to 0x48
by connecting the ADDR pin to ground. If you have selected a
differnet address you will need to modify the constructor call
to ADS1115 to specify a different address like:
adc = ADS1115(i2c, address=0x49)
This example also assumes the default range of the ADS of
+- 4.096V. If your voltage input is in a different range
this can also be specified in the constructor call. For
example if your input voltage is within the range of +-2.048V
you would call the constructor like this:
adc = ADS1115(i2c, gain=PGA_2_048V)
A list of available gain options can be found in ADS1115.py
around line27.
'''
import pycom
from machine import I2C, Pin, Timer
from network import WLAN
from ADS1115 import ADS1115
# Use the built in LED as a status indicator
status_led = Pin('G16', mode=Pin.OUT, value=1)
# Setup ADS1115 using defaults (0x48 address and 4.096V max range)
i2c = I2C(0, I2C.MASTER)
adc = ADS1115(i2c)
def read_adc(alarm):
if status_led:
status_led.toggle()
print("\nChannel 0 voltage: {}V".format(adc.get_voltage(0)))
print("Channel 0 ADC value: {}\n".format(adc.read(0)))
def main():
# Use the RGB LED as an indicator of WiFi status
pycom.heartbeat(False)
wlan = WLAN()
if wlan.isconnected():
pycom.rgbled(0x000f00)
else:
pycom.rgbled(0x0f0000)
# Read the ADC on a 5 second interval
Timer.Alarm(read_adc, 5, periodic=True)
main()
@astcode

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commented Mar 15, 2018

Can you please give an example of how to use this? I am a noob to Pycom ie. GPy/FiPy and I am wanting to get the reading from a few sensors.

@sidwarkd

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Owner Author

commented Mar 24, 2018

@astcode I've updated the gist to include a simple example of reading from channel 0 on the ADS1115

@astcode

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commented Mar 25, 2018

Thank you. It works perfectly.

@Borbonjuggler

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commented Mar 3, 2019

Thanks a Lot

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