On Sun, 10 Nov 2019 18:17:13 -0800 (PST), in
gmane.comp.hardware.beagleboard.user Mala Dies
<[email protected]> wrote:
Just some stuff I scratched together -- all untested (read the
comments)
-=-=-=- adc-1.py
#!/usr/bin/env python3
"""
adc-1.py ADC example using MCP3008 and mysterious LDRII library
November 11, 2019 Dennis L Bieber
*** UNTESTED **
Not only do I not have access to an MCP3008 ADC chip, I have not
been able to find the LDRII (Light Dependent Resistor?) library
supporting said chip.
The API used is based upon postings in comp.lang.python by one
"Mala Dies" who, it seems, is having a truly bad day
This code reads all 8 channels of the MCP3008. It may be worth
checking the data sheet for the chip to determine which state
draws the least current and using a 10KOhm or higher resister to
pull-up/pull-down the unused inputs.
"""
import time
from LDRII import MCP3008
#constants from spec sheets
ADC_BITS = 10
ADC_REF = 3.3
ADC_CHANNELS = 8
T_DELTA = 5.0
#derived constants
ADC_MAX = (2 ** ADC_BITS) - 1
ADC_VSTEP = ADC_REF / ADC_MAX
#create ADC instance
adc = MCP3008()
t0 = t = time.time()
while True:
print("\nT: %16.2f" % (time.time() - t0))
for channel in range(ADC_CHANNELS):
raw = adc.read(channel = channel)
print("\tChannel: %2d\tCount: %4d\tVoltage: %6.3f"
% (channel, raw, raw * ADC_VSTEP))
t += T_DELTA
time.sleep(t - time.time())
-=-=-=-
-=-=-=- adc-2.py
#!/usr/bin/env python3
"""
adc-2.py ADC example using MCP3008 and Adafruit_Blinka
and Adafruit_CircuitPython_MCP3xxx libraries
November 11, 2019 Dennis L Bieber
*** UNTESTED **
I do not have access to an MCP3008 ADC chip
*** PREREQUISITES ***
sudo pip3 install adafruit_blinka (might be adafruit-blinka)
sudo pip3 install adafruit-circuitpython-mcp3xxx
This code reads all 8 channels of the MCP3008. It may be worth
checking the data sheet for the chip to determine which state
draws the least current and using a 10KOhm or higher resister to
pull-up/pull-down the unused inputs.
"""
import time
import busio
import digitalio
import board
import adafruit_mcp3xxx.mcp3008 as MCP
from adafruit_mcp3xxx.analog_in import AnalogIn
#constants from spec sheets
ADC_REF = 3.3
ADC_CHANNELS = 8
T_DELTA = 5.0
#create the SPI bus and ChipSelect
spi = busio.SPI(clock=board.SCK, MISO=board.MISO, MOSI=board.MOSI)
cs = digitalio.DigitalInOut(board.DS)
#create ADC instance (note: ref_voltage default is 3.3 if not supplied)
adc = MCP.MCP3008(spi, cs, ref_voltage = ADC_REF)
#create ADC channel instances -- relies on MCP.P0 = 0, etc.
channels = [ AnalogIn(adc, chan) for chan in range(ADC_CHANNELS) ]
t0 = t = time.time()
while True:
print("\nT: %16.2f" % (time.time() - t0))
for channel in channels:
#while a 10-bit ADC chip, the raw counts are scaled to 65472
raw, voltage = channels[channel].value, channels[channel].voltage
print("\tChannel: %2d\tCount: %4d\tVoltage: %6.3f"
% (channel, raw, voltage))
t += T_DELTA
time.sleep(t - time.time())
-=-=-=-
-=-=-=- adc-3.py
#!/usr/bin/env python3
"""
adc-3.py ADC example using native BBB ADC and
adafruit_bbio library
November 11, 2019 Dennis L Bieber
*** UNTESTED **
While I do have BBB, I have not taken time to wire a circuit
*** WARNING ***
BBB ADC inputs can be damaged by signals greater than 1.8V
It would perhaps be best to use a voltage divider circuit
with the 3.3V yielding a maximum of 1.65V [giving up a few
counts for the last 0.15V]
This code reads all 7 channels of the BBB. It may be worth
checking the data sheet for the chip to determine which state
draws the least current and using a 10KOhm or higher resister to
pull-up/pull-down the unused inputs.
"""
import time
import Adafruit_BBIO.ADC as ADC
#constants from spec sheets
ADC_REF = 1.8
#pins equivalent to AIN0..AIN6
CHANNELS = [ "P9_39", "P9_40", "P9_37",
"P9_38", "P9_33", "p9_36",
"P9_35" ]
T_DELTA = 5.0
#initialize ADC system
ADC.setup()
t0 = t = time.time()
while True:
print("\nT: %16.2f" % (time.time() - t0))
for channel in channels:
#a documented bug in ADC driver recommends one needs to
#read twice to get latest value, I'm presuming that does
#not mean both .read() and .read_raw() need to be repeated
jnk = ADC.read(channel)
raw, voltage = ADC.read_raw(channel), ADC.read(channel)
#"voltage" is scaled 0.0 .. 1.0, so multiply by reference
print("\tChannel: %2d\tCount: %4d\tVoltage: %6.3f"
% (channel, raw, voltage * ADC_REF))
t += T_DELTA
time.sleep(t - time.time())
-=-=-=-
--
Dennis L Bieber
--
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