357 lines
13 KiB
Python
357 lines
13 KiB
Python
# Support for common SPI based thermocouple and RTD temperature sensors
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#
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# Copyright (C) 2018 Petri Honkala <cruwaller@gmail.com>
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# Copyright (C) 2018 Kevin O'Connor <kevin@koconnor.net>
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#
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# This file may be distributed under the terms of the GNU GPLv3 license.
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import math, logging
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from . import bus
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######################################################################
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# SensorBase
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######################################################################
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REPORT_TIME = 0.300
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MAX_INVALID_COUNT = 3
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class SensorBase:
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def __init__(self, config, chip_type, config_cmd=None, spi_mode=1):
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self.printer = config.get_printer()
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self.chip_type = chip_type
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self._callback = None
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self.min_sample_value = self.max_sample_value = 0
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self._report_clock = 0
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self.spi = bus.MCU_SPI_from_config(
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config, spi_mode, pin_option="sensor_pin", default_speed=4000000)
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if config_cmd is not None:
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self.spi.spi_send(config_cmd)
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self.mcu = mcu = self.spi.get_mcu()
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# Reader chip configuration
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self.oid = oid = mcu.create_oid()
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mcu.register_response(self._handle_spi_response,
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"thermocouple_result", oid)
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mcu.register_config_callback(self._build_config)
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def setup_minmax(self, min_temp, max_temp):
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adc_range = [self.calc_adc(min_temp), self.calc_adc(max_temp)]
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self.min_sample_value = min(adc_range)
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self.max_sample_value = max(adc_range)
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def setup_callback(self, cb):
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self._callback = cb
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def get_report_time_delta(self):
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return REPORT_TIME
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def _build_config(self):
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self.mcu.add_config_cmd(
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"config_thermocouple oid=%u spi_oid=%u thermocouple_type=%s" % (
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self.oid, self.spi.get_oid(), self.chip_type))
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clock = self.mcu.get_query_slot(self.oid)
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self._report_clock = self.mcu.seconds_to_clock(REPORT_TIME)
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self.mcu.add_config_cmd(
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"query_thermocouple oid=%u clock=%u rest_ticks=%u"
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" min_value=%u max_value=%u max_invalid_count=%u" % (
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self.oid, clock, self._report_clock,
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self.min_sample_value, self.max_sample_value,
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MAX_INVALID_COUNT), is_init=True)
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def _handle_spi_response(self, params):
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if params['fault']:
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self.handle_fault(params['value'], params['fault'])
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return
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temp = self.calc_temp(params['value'])
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next_clock = self.mcu.clock32_to_clock64(params['next_clock'])
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last_read_clock = next_clock - self._report_clock
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last_read_time = self.mcu.clock_to_print_time(last_read_clock)
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self._callback(last_read_time, temp)
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def report_fault(self, msg):
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logging.warn(msg)
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######################################################################
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# MAX31856 thermocouple
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######################################################################
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MAX31856_CR0_REG = 0x00
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MAX31856_CR0_AUTOCONVERT = 0x80
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MAX31856_CR0_1SHOT = 0x40
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MAX31856_CR0_OCFAULT1 = 0x20
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MAX31856_CR0_OCFAULT0 = 0x10
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MAX31856_CR0_CJ = 0x08
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MAX31856_CR0_FAULT = 0x04
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MAX31856_CR0_FAULTCLR = 0x02
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MAX31856_CR0_FILT50HZ = 0x01
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MAX31856_CR0_FILT60HZ = 0x00
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MAX31856_CR1_REG = 0x01
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MAX31856_CR1_AVGSEL1 = 0x00
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MAX31856_CR1_AVGSEL2 = 0x10
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MAX31856_CR1_AVGSEL4 = 0x20
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MAX31856_CR1_AVGSEL8 = 0x30
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MAX31856_CR1_AVGSEL16 = 0x70
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MAX31856_MASK_REG = 0x02
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MAX31856_MASK_COLD_JUNCTION_HIGH_FAULT = 0x20
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MAX31856_MASK_COLD_JUNCTION_LOW_FAULT = 0x10
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MAX31856_MASK_THERMOCOUPLE_HIGH_FAULT = 0x08
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MAX31856_MASK_THERMOCOUPLE_LOW_FAULT = 0x04
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MAX31856_MASK_VOLTAGE_UNDER_OVER_FAULT = 0x02
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MAX31856_MASK_THERMOCOUPLE_OPEN_FAULT = 0x01
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MAX31856_CJHF_REG = 0x03
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MAX31856_CJLF_REG = 0x04
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MAX31856_LTHFTH_REG = 0x05
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MAX31856_LTHFTL_REG = 0x06
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MAX31856_LTLFTH_REG = 0x07
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MAX31856_LTLFTL_REG = 0x08
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MAX31856_CJTO_REG = 0x09
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MAX31856_CJTH_REG = 0x0A
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MAX31856_CJTL_REG = 0x0B
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MAX31856_LTCBH_REG = 0x0C
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MAX31856_LTCBM_REG = 0x0D
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MAX31856_LTCBL_REG = 0x0E
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MAX31856_SR_REG = 0x0F
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MAX31856_FAULT_CJRANGE = 0x80 # Cold Junction out of range
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MAX31856_FAULT_TCRANGE = 0x40 # Thermocouple out of range
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MAX31856_FAULT_CJHIGH = 0x20 # Cold Junction High
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MAX31856_FAULT_CJLOW = 0x10 # Cold Junction Low
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MAX31856_FAULT_TCHIGH = 0x08 # Thermocouple Low
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MAX31856_FAULT_TCLOW = 0x04 # Thermocouple Low
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MAX31856_FAULT_OVUV = 0x02 # Under Over Voltage
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MAX31856_FAULT_OPEN = 0x01
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MAX31856_SCALE = 5
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MAX31856_MULT = 0.0078125
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class MAX31856(SensorBase):
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def __init__(self, config):
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SensorBase.__init__(self, config, "MAX31856",
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self.build_spi_init(config))
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def handle_fault(self, adc, fault):
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if fault & MAX31856_FAULT_CJRANGE:
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self.report_fault("Max31856: Cold Junction Range Fault")
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if fault & MAX31856_FAULT_TCRANGE:
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self.report_fault("Max31856: Thermocouple Range Fault")
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if fault & MAX31856_FAULT_CJHIGH:
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self.report_fault("Max31856: Cold Junction High Fault")
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if fault & MAX31856_FAULT_CJLOW:
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self.report_fault("Max31856: Cold Junction Low Fault")
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if fault & MAX31856_FAULT_TCHIGH:
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self.report_fault("Max31856: Thermocouple High Fault")
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if fault & MAX31856_FAULT_TCLOW:
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self.report_fault("Max31856: Thermocouple Low Fault")
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if fault & MAX31856_FAULT_OVUV:
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self.report_fault("Max31856: Over/Under Voltage Fault")
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if fault & MAX31856_FAULT_OPEN:
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self.report_fault("Max31856: Thermocouple Open Fault")
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def calc_temp(self, adc):
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adc = adc >> MAX31856_SCALE
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# Fix sign bit:
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if adc & 0x40000:
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adc = ((adc & 0x3FFFF) + 1) * -1
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temp = MAX31856_MULT * adc
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return temp
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def calc_adc(self, temp):
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adc = int( ( temp / MAX31856_MULT ) + 0.5 ) # convert to ADC value
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adc = max(0, min(0x3FFFF, adc)) << MAX31856_SCALE
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return adc
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def build_spi_init(self, config):
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cmds = []
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value = MAX31856_CR0_AUTOCONVERT
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if config.getboolean('tc_use_50Hz_filter', False):
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value |= MAX31856_CR0_FILT50HZ
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cmds.append(0x80 + MAX31856_CR0_REG)
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cmds.append(value)
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types = {
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"B" : 0b0000,
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"E" : 0b0001,
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"J" : 0b0010,
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"K" : 0b0011,
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"N" : 0b0100,
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"R" : 0b0101,
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"S" : 0b0110,
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"T" : 0b0111,
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}
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value = config.getchoice('tc_type', types, default="K")
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averages = {
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1 : MAX31856_CR1_AVGSEL1,
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2 : MAX31856_CR1_AVGSEL2,
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4 : MAX31856_CR1_AVGSEL4,
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8 : MAX31856_CR1_AVGSEL8,
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16 : MAX31856_CR1_AVGSEL16
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}
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value |= config.getchoice('tc_averaging_count', averages, 1)
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cmds.append(value)
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value = (MAX31856_MASK_VOLTAGE_UNDER_OVER_FAULT |
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MAX31856_MASK_THERMOCOUPLE_OPEN_FAULT)
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cmds.append(value)
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return cmds
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######################################################################
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# MAX31855 thermocouple
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######################################################################
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MAX31855_SCALE = 18
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MAX31855_MULT = 0.25
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class MAX31855(SensorBase):
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def __init__(self, config):
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SensorBase.__init__(self, config, "MAX31855", spi_mode=0)
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def handle_fault(self, adc, fault):
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if fault & 0x1:
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self.report_fault("MAX31855 : Open Circuit")
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if fault & 0x2:
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self.report_fault("MAX31855 : Short to GND")
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if fault & 0x4:
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self.report_fault("MAX31855 : Short to Vcc")
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def calc_temp(self, adc):
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adc = adc >> MAX31855_SCALE
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# Fix sign bit:
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if adc & 0x2000:
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adc = ((adc & 0x1FFF) + 1) * -1
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temp = MAX31855_MULT * adc
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return temp
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def calc_adc(self, temp):
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adc = int( ( temp / MAX31855_MULT ) + 0.5 ) # convert to ADC value
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adc = max(0, min(0x1FFF, adc)) << MAX31855_SCALE
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return adc
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######################################################################
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# MAX6675 thermocouple
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######################################################################
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MAX6675_SCALE = 3
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MAX6675_MULT = 0.25
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class MAX6675(SensorBase):
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def __init__(self, config):
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SensorBase.__init__(self, config, "MAX6675", spi_mode=0)
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def handle_fault(self, adc, fault):
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if fault & 0x02:
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self.report_fault("Max6675 : Device ID error")
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if fault & 0x04:
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self.report_fault("Max6675 : Thermocouple Open Fault")
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def calc_temp(self, adc):
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adc = adc >> MAX6675_SCALE
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# Fix sign bit:
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if adc & 0x2000:
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adc = ((adc & 0x1FFF) + 1) * -1
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temp = MAX6675_MULT * adc
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return temp
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def calc_adc(self, temp):
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adc = int( ( temp / MAX6675_MULT ) + 0.5 ) # convert to ADC value
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adc = max(0, min(0x1FFF, adc)) << MAX6675_SCALE
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return adc
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######################################################################
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# MAX31865 (RTD sensor)
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######################################################################
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MAX31865_CONFIG_REG = 0x00
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MAX31865_RTDMSB_REG = 0x01
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MAX31865_RTDLSB_REG = 0x02
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MAX31865_HFAULTMSB_REG = 0x03
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MAX31865_HFAULTLSB_REG = 0x04
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MAX31865_LFAULTMSB_REG = 0x05
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MAX31865_LFAULTLSB_REG = 0x06
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MAX31865_FAULTSTAT_REG = 0x07
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MAX31865_CONFIG_BIAS = 0x80
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MAX31865_CONFIG_MODEAUTO = 0x40
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MAX31865_CONFIG_1SHOT = 0x20
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MAX31865_CONFIG_3WIRE = 0x10
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MAX31865_CONFIG_FAULTCLEAR = 0x02
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MAX31865_CONFIG_FILT50HZ = 0x01
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MAX31865_FAULT_HIGHTHRESH = 0x80
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MAX31865_FAULT_LOWTHRESH = 0x40
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MAX31865_FAULT_REFINLOW = 0x20
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MAX31865_FAULT_REFINHIGH = 0x10
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MAX31865_FAULT_RTDINLOW = 0x08
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MAX31865_FAULT_OVUV = 0x04
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MAX31865_ADC_MAX = 1<<15
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# Callendar-Van Dusen constants for platinum resistance thermometers (RTD)
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CVD_A = 3.9083e-3
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CVD_B = -5.775e-7
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class MAX31865(SensorBase):
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def __init__(self, config):
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rtd_nominal_r = config.getfloat('rtd_nominal_r', 100., above=0.)
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rtd_reference_r = config.getfloat('rtd_reference_r', 430., above=0.)
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adc_to_resist = rtd_reference_r / float(MAX31865_ADC_MAX)
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self.adc_to_resist_div_nominal = adc_to_resist / rtd_nominal_r
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self.config_reg = self.build_spi_init(config)
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SensorBase.__init__(self, config, "MAX31865", self.config_reg)
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def handle_fault(self, adc, fault):
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if fault & 0x80:
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self.report_fault("Max31865 RTD input is disconnected")
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if fault & 0x40:
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self.report_fault("Max31865 RTD input is shorted")
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if fault & 0x20:
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self.report_fault(
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"Max31865 VREF- is greater than 0.85 * VBIAS, FORCE- open")
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if fault & 0x10:
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self.report_fault(
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"Max31865 VREF- is less than 0.85 * VBIAS, FORCE- open")
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if fault & 0x08:
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self.report_fault(
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"Max31865 VRTD- is less than 0.85 * VBIAS, FORCE- open")
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if fault & 0x04:
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self.report_fault("Max31865 Overvoltage or undervoltage fault")
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if not fault & 0xfc:
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self.report_fault("Max31865 Unspecified error")
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# Attempt to clear the fault
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self.spi.spi_send(self.config_reg)
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def calc_temp(self, adc):
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adc = adc >> 1 # remove fault bit
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R_div_nominal = adc * self.adc_to_resist_div_nominal
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# Resistance (relative to rtd_nominal_r) is calculated using:
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# R_div_nominal = 1. + CVD_A * temp + CVD_B * temp**2
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# Solve for temp using quadratic equation:
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# temp = (-b +- sqrt(b**2 - 4ac)) / 2a
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discriminant = math.sqrt(CVD_A**2 - 4. * CVD_B * (1. - R_div_nominal))
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temp = (-CVD_A + discriminant) / (2. * CVD_B)
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return temp
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def calc_adc(self, temp):
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# Calculate relative resistance via Callendar-Van Dusen formula:
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# resistance = rtd_nominal_r * (1 + CVD_A * temp + CVD_B * temp**2)
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temp = min(temp, 1768.3) # Melting point of platinum
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R_div_nominal = 1. + CVD_A * temp + CVD_B * temp * temp
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adc = int(R_div_nominal / self.adc_to_resist_div_nominal + 0.5)
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adc = max(0, min(MAX31865_ADC_MAX - 1, adc))
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adc = adc << 1 # Add fault bit
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return adc
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def build_spi_init(self, config):
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value = (MAX31865_CONFIG_BIAS |
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MAX31865_CONFIG_MODEAUTO |
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MAX31865_CONFIG_FAULTCLEAR)
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if config.getboolean('rtd_use_50Hz_filter', False):
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value |= MAX31865_CONFIG_FILT50HZ
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if config.getint('rtd_num_of_wires', 2) == 3:
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value |= MAX31865_CONFIG_3WIRE
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cmd = 0x80 + MAX31865_CONFIG_REG
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return [cmd, value]
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######################################################################
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# Sensor registration
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######################################################################
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Sensors = {
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"MAX6675": MAX6675,
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"MAX31855": MAX31855,
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"MAX31856": MAX31856,
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"MAX31865": MAX31865,
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}
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def load_config(config):
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# Register sensors
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pheaters = config.get_printer().load_object(config, "heaters")
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for name, klass in Sensors.items():
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pheaters.add_sensor_factory(name, klass)
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