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# Obtain temperature using linear interpolation of ADC values
#
# Copyright (C) 2016-2018 Kevin O'Connor <kevin@koconnor.net>
#
# This file may be distributed under the terms of the GNU GPLv3 license.
import logging, bisect
######################################################################
# Interface between MCU adc and heater temperature callbacks
######################################################################
SAMPLE_TIME = 0.001
SAMPLE_COUNT = 8
REPORT_TIME = 0.300
RANGE_CHECK_COUNT = 4
# Interface between ADC and heater temperature callbacks
class PrinterADCtoTemperature:
def __init__(self, config, adc_convert):
self.adc_convert = adc_convert
ppins = config.get_printer().lookup_object('pins')
self.mcu_adc = ppins.setup_pin('adc', config.get('sensor_pin'))
self.mcu_adc.setup_adc_callback(REPORT_TIME, self.adc_callback)
def setup_callback(self, temperature_callback):
self.temperature_callback = temperature_callback
def get_report_time_delta(self):
return REPORT_TIME
def adc_callback(self, read_time, read_value):
temp = self.adc_convert.calc_temp(read_value)
self.temperature_callback(read_time + SAMPLE_COUNT * SAMPLE_TIME, temp)
def setup_minmax(self, min_temp, max_temp):
adc_range = [self.adc_convert.calc_adc(t) for t in [min_temp, max_temp]]
self.mcu_adc.setup_minmax(SAMPLE_TIME, SAMPLE_COUNT,
minval=min(adc_range), maxval=max(adc_range),
range_check_count=RANGE_CHECK_COUNT)
######################################################################
# Linear interpolation
######################################################################
# Helper code to perform linear interpolation
class LinearInterpolate:
def __init__(self, samples):
self.keys = []
self.slopes = []
last_key = last_value = None
for key, value in sorted(samples):
if last_key is None:
last_key = key
last_value = value
continue
if key <= last_key:
raise ValueError("duplicate value")
gain = (value - last_value) / (key - last_key)
offset = last_value - last_key * gain
if self.slopes and self.slopes[-1] == (gain, offset):
continue
last_value = value
last_key = key
self.keys.append(key)
self.slopes.append((gain, offset))
if not self.keys:
raise ValueError("need at least two samples")
self.keys.append(9999999999999.)
self.slopes.append(self.slopes[-1])
def interpolate(self, key):
pos = bisect.bisect(self.keys, key)
gain, offset = self.slopes[pos]
return key * gain + offset
def reverse_interpolate(self, value):
values = [key * gain + offset for key, (gain, offset) in zip(
self.keys, self.slopes)]
if values[0] < values[-2]:
valid = [i for i in range(len(values)) if values[i] >= value]
else:
valid = [i for i in range(len(values)) if values[i] <= value]
gain, offset = self.slopes[min(valid + [len(values) - 1])]
return (value - offset) / gain
######################################################################
# Linear voltage to temperature converter
######################################################################
# Linear style conversion chips calibrated with two temp measurements
class LinearVoltage:
def __init__(self, config, params):
adc_voltage = config.getfloat('adc_voltage', 5., above=0.)
samples = []
for temp, volt in params:
adc = volt / adc_voltage
if adc < 0. or adc > 1.:
logging.warn("Ignoring adc sample %.3f/%.3f in heater %s",
temp, volt, config.get_name())
continue
samples.append((adc, temp))
try:
li = LinearInterpolate(samples)
except ValueError as e:
raise config.error("adc_temperature %s in heater %s" % (
str(e), config.get_name()))
self.calc_temp = li.interpolate
self.calc_adc = li.reverse_interpolate
# Custom defined sensors from the config file
class CustomLinearVoltage:
def __init__(self, config):
self.name = " ".join(config.get_name().split()[1:])
self.params = []
for i in range(1, 1000):
t = config.getfloat("temperature%d" % (i,), None)
if t is None:
break
v = config.getfloat("voltage%d" % (i,))
self.params.append((t, v))
def create(self, config):
lv = LinearVoltage(config, self.params)
return PrinterADCtoTemperature(config, lv)
######################################################################
# Linear resistance to temperature converter
######################################################################
# Linear resistance calibrated with two temp measurements
class LinearResistance:
def __init__(self, config, samples):
self.pullup = config.getfloat('pullup_resistor', 4700., above=0.)
try:
self.li = LinearInterpolate(samples)
except ValueError as e:
raise config.error("adc_temperature %s in heater %s" % (
str(e), config.get_name()))
def calc_temp(self, adc):
# Calculate temperature from adc
adc = max(.00001, min(.99999, adc))
r = self.pullup * adc / (1.0 - adc)
return self.li.interpolate(r)
def calc_adc(self, temp):
# Calculate adc reading from a temperature
r = self.li.reverse_interpolate(temp)
return r / (self.pullup + r)
# Custom defined sensors from the config file
class CustomLinearResistance:
def __init__(self, config):
self.name = " ".join(config.get_name().split()[1:])
self.samples = []
for i in range(1, 1000):
t = config.getfloat("temperature%d" % (i,), None)
if t is None:
break
r = config.getfloat("resistance%d" % (i,))
self.samples.append((r, t))
def create(self, config):
lr = LinearResistance(config, self.samples)
return PrinterADCtoTemperature(config, lr)
######################################################################
# Default sensors
######################################################################
AD595 = [
(0., .0027), (10., .101), (20., .200), (25., .250), (30., .300),
(40., .401), (50., .503), (60., .605), (80., .810), (100., 1.015),
(120., 1.219), (140., 1.420), (160., 1.620), (180., 1.817), (200., 2.015),
(220., 2.213), (240., 2.413), (260., 2.614), (280., 2.817), (300., 3.022),
(320., 3.227), (340., 3.434), (360., 3.641), (380., 3.849), (400., 4.057),
(420., 4.266), (440., 4.476), (460., 4.686), (480., 4.896)
]
PT100 = [
(0, 0.00), (1, 1.11), (10, 1.15), (20, 1.20), (30, 1.24), (40, 1.28),
(50, 1.32), (60, 1.36), (70, 1.40), (80, 1.44), (90, 1.48), (100, 1.52),
(110, 1.56), (120, 1.61), (130, 1.65), (140, 1.68), (150, 1.72),
(160, 1.76), (170, 1.80), (180, 1.84), (190, 1.88), (200, 1.92),
(210, 1.96), (220, 2.00), (230, 2.04), (240, 2.07), (250, 2.11),
(260, 2.15), (270, 2.18), (280, 2.22), (290, 2.26), (300, 2.29),
(310, 2.33), (320, 2.37), (330, 2.41), (340, 2.44), (350, 2.48),
(360, 2.51), (370, 2.55), (380, 2.58), (390, 2.62), (400, 2.66),
(500, 3.00), (600, 3.33), (700, 3.63), (800, 3.93), (900, 4.21),
(1000, 4.48), (1100, 4.73)
]
def load_config(config):
# Register default sensors
pheater = config.get_printer().lookup_object("heater")
for sensor_type, params in [("AD595", AD595), ("PT100 INA826", PT100)]:
func = (lambda config, params=params:
PrinterADCtoTemperature(config, LinearVoltage(config, params)))
pheater.add_sensor(sensor_type, func)
def load_config_prefix(config):
if config.get("resistance1", None) is None:
custom_sensor = CustomLinearVoltage(config)
else:
custom_sensor = CustomLinearResistance(config)
pheater = config.get_printer().lookup_object("heater")
pheater.add_sensor(custom_sensor.name, custom_sensor.create)
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