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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
SAMPLE_TIME = 0.001
SAMPLE_COUNT = 8
REPORT_TIME = 0.300
# Linear style conversion chips calibrated with two temp measurements
class Linear:
def __init__(self, config, params):
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)
self.temperature_callback = None
self.adc_samples = []
self.slope_samples = []
self.calc_coefficients(config, params)
def calc_coefficients(self, config, params):
adc_voltage = config.getfloat('adc_voltage', 5., above=0.)
last_volt = last_temp = None
for volt, temp in sorted([(v, t) for t, v 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
if last_volt is None:
last_volt = volt
last_temp = temp
continue
if volt <= last_volt:
raise config.error("adc_temperature duplicate voltage")
slope = (temp - last_temp) / (volt - last_volt)
gain = adc_voltage * slope
offset = last_temp - last_volt * slope
if self.slope_samples and self.slope_samples[-1] == (gain, offset):
continue
last_temp = temp
last_volt = volt
self.adc_samples.append(adc)
self.slope_samples.append((gain, offset))
if not self.adc_samples:
raise config.error(
"adc_temperature needs two volt and temperature measurements")
self.adc_samples[-1] = 1.
def setup_minmax(self, min_temp, max_temp):
adc_range = [self.calc_adc(min_temp), self.calc_adc(max_temp)]
self.mcu_adc.setup_minmax(SAMPLE_TIME, SAMPLE_COUNT,
minval=min(adc_range), maxval=max(adc_range))
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):
pos = bisect.bisect(self.adc_samples, read_value)
gain, offset = self.slope_samples[pos]
temp = read_value * gain + offset
self.temperature_callback(read_time + SAMPLE_COUNT * SAMPLE_TIME, temp)
def calc_adc(self, temp):
temps = [adc * gain + offset for adc, (gain, offset) in zip(
self.adc_samples, self.slope_samples)]
if temps[0] < temps[-1]:
pos = min([i for i in range(len(temps)) if temps[i] >= temp]
+ [len(temps) - 1])
else:
pos = min([i for i in range(len(temps)) if temps[i] <= temp]
+ [len(temps) - 1])
gain, offset = self.slope_samples[pos]
return (temp - offset) / gain
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)
]
def load_config(config):
# Register default sensors
pheater = config.get_printer().lookup_object("heater")
for sensor_type, params in [("AD595", AD595)]:
func = (lambda config, params=params: Linear(config, params))
pheater.add_sensor(sensor_type, func)
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