From b2caa486c5a120fa34d9447b617ea89aca1c1c99 Mon Sep 17 00:00:00 2001
From: Kevin O'Connor <kevin@koconnor.net>
Date: Mon, 9 Apr 2018 14:02:59 -0400
Subject: [PATCH] adc_temperature: Support multiple ranges for ADC lookup
Instead of supporting a single linear range for the temperature
lookup, allow multiple ranges to be defined. This makes the lookup
more accurate when a full lookup table is available.
Update the AD595 sensor to use the full table defined in its spec.
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
---
klippy/extras/adc_temperature.py | 64 +++++++++++++++++++++++++++-----
1 file changed, 54 insertions(+), 10 deletions(-)
diff --git a/klippy/extras/adc_temperature.py b/klippy/extras/adc_temperature.py
index 1006944d5..9880a09cb 100644
--- a/klippy/extras/adc_temperature.py
+++ b/klippy/extras/adc_temperature.py
@@ -3,6 +3,7 @@
# 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
@@ -11,14 +12,41 @@ REPORT_TIME = 0.300
# Linear style conversion chips calibrated with two temp measurements
class Linear:
def __init__(self, config, params):
- adc_voltage = config.getfloat('adc_voltage', 5., above=0.)
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
- slope = (params['t2'] - params['t1']) / (params['v2'] - params['v1'])
- self.gain = adc_voltage * slope
- self.offset = params['t1'] - params['v1'] * slope
+ 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,
@@ -28,18 +56,34 @@ class Linear:
def get_report_time_delta(self):
return REPORT_TIME
def adc_callback(self, read_time, read_value):
- temp = read_value * self.gain + self.offset
+ 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):
- return (temp - self.offset) / self.gain
+ 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
-Sensors = {
- "AD595": { 't1': 25., 'v1': .25, 't2': 300., 'v2': 3.022 },
-}
+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 Sensors.items():
+ for sensor_type, params in [("AD595", AD595)]:
func = (lambda config, params=params: Linear(config, params))
pheater.add_sensor(sensor_type, func)