klipper/klippy/extras/adc_temperature.py

# 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)