kopia lustrzana https://github.com/botheredbybees/kilnController
173 wiersze
6.2 KiB
Python
173 wiersze
6.2 KiB
Python
#!/usr/bin/python
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import RPi.GPIO as GPIO
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class MAX31855(object):
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'''Python driver for [MAX38155 Cold-Junction Compensated Thermocouple-to-Digital Converter](http://www.maximintegrated.com/datasheet/index.mvp/id/7273)
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Requires:
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- The [GPIO Library](https://code.google.com/p/raspberry-gpio-python/) (Already on most Raspberry Pi OS builds)
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- A [Raspberry Pi](http://www.raspberrypi.org/)
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'''
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def __init__(self, cs_pin, clock_pin, data_pin, units = "c", board = GPIO.BCM):
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'''Initialize Soft (Bitbang) SPI bus
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Parameters:
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- cs_pin: Chip Select (CS) / Slave Select (SS) pin (Any GPIO)
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- clock_pin: Clock (SCLK / SCK) pin (Any GPIO)
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- data_pin: Data input (SO / MOSI) pin (Any GPIO)
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- units: (optional) unit of measurement to return. ("c" (default) | "k" | "f")
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- board: (optional) pin numbering method as per RPi.GPIO library (GPIO.BCM (default) | GPIO.BOARD)
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'''
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self.cs_pin = cs_pin
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self.clock_pin = clock_pin
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self.data_pin = data_pin
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self.units = units
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self.data = None
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self.board = board
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# Initialize needed GPIO
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GPIO.setmode(self.board)
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GPIO.setup(self.cs_pin, GPIO.OUT)
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GPIO.setup(self.clock_pin, GPIO.OUT)
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GPIO.setup(self.data_pin, GPIO.IN)
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# Pull chip select high to make chip inactive
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GPIO.output(self.cs_pin, GPIO.HIGH)
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def get(self):
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'''Reads SPI bus and returns current value of thermocouple.'''
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self.read()
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self.checkErrors()
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return getattr(self, "to_" + self.units)(self.data_to_tc_temperature())
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def get_rj(self):
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'''Reads SPI bus and returns current value of reference junction.'''
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self.read()
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return getattr(self, "to_" + self.units)(self.data_to_rj_temperature())
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def read(self):
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'''Reads 32 bits of the SPI bus & stores as an integer in self.data.'''
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bytesin = 0
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# Select the chip
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GPIO.output(self.cs_pin, GPIO.LOW)
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# Read in 32 bits
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for i in range(32):
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GPIO.output(self.clock_pin, GPIO.LOW)
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bytesin = bytesin << 1
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if (GPIO.input(self.data_pin)):
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bytesin = bytesin | 1
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GPIO.output(self.clock_pin, GPIO.HIGH)
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# Unselect the chip
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GPIO.output(self.cs_pin, GPIO.HIGH)
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# Save data
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self.data = bytesin
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def checkErrors(self, data_32 = None):
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'''Checks error bits to see if there are any SCV, SCG, or OC faults'''
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if data_32 is None:
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data_32 = self.data
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anyErrors = (data_32 & 0x10000) != 0 # Fault bit, D16
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noConnection = (data_32 & 0x00000001) != 0 # OC bit, D0
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shortToGround = (data_32 & 0x00000002) != 0 # SCG bit, D1
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shortToVCC = (data_32 & 0x00000004) != 0 # SCV bit, D2
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if anyErrors:
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if noConnection:
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# raise MAX31855Error("No Connection")
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print("MAX31855Error(No Connection)")
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elif shortToGround:
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#raise MAX31855Error("Thermocouple short to ground")
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print("Thermocouple reports short to ground")
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elif shortToVCC:
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raise MAX31855Error("Thermocouple short to VCC")
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else:
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# Perhaps another SPI device is trying to send data?
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# Did you remember to initialize all other SPI devices?
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raise MAX31855Error("Unknown Error")
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def data_to_tc_temperature(self, data_32 = None):
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'''Takes an integer and returns a thermocouple temperature in celsius.'''
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if data_32 is None:
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data_32 = self.data
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tc_data = ((data_32 >> 18) & 0x3FFF)
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return self.convert_tc_data(tc_data)
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def data_to_rj_temperature(self, data_32 = None):
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'''Takes an integer and returns a reference junction temperature in celsius.'''
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if data_32 is None:
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data_32 = self.data
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rj_data = ((data_32 >> 4) & 0xFFF)
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return self.convert_rj_data(rj_data)
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def convert_tc_data(self, tc_data):
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'''Convert thermocouple data to a useful number (celsius).'''
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if tc_data & 0x2000:
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# two's compliment
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without_resolution = ~tc_data & 0x1FFF
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without_resolution += 1
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without_resolution *= -1
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else:
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without_resolution = tc_data & 0x1FFF
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return without_resolution * 0.25
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def convert_rj_data(self, rj_data):
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'''Convert reference junction data to a useful number (celsius).'''
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if rj_data & 0x800:
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without_resolution = ~rj_data & 0x7FF
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without_resolution += 1
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without_resolution *= -1
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else:
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without_resolution = rj_data & 0x7FF
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return without_resolution * 0.0625
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def to_c(self, celsius):
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'''Celsius passthrough for generic to_* method.'''
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return celsius
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def to_k(self, celsius):
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'''Convert celsius to kelvin.'''
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return celsius + 273.15
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def to_f(self, celsius):
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'''Convert celsius to fahrenheit.'''
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return celsius * 9.0/5.0 + 32
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def cleanup(self):
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'''Selective GPIO cleanup'''
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GPIO.setup(self.cs_pin, GPIO.IN)
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GPIO.setup(self.clock_pin, GPIO.IN)
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class MAX31855Error(Exception):
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def __init__(self, value):
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self.value = value
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def __str__(self):
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return repr(self.value)
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if __name__ == "__main__":
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# Multi-chip example
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import time
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cs_pins = [4, 17, 18, 24]
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clock_pin = 23
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data_pin = 22
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units = "f"
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thermocouples = []
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for cs_pin in cs_pins:
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thermocouples.append(MAX31855(cs_pin, clock_pin, data_pin, units))
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running = True
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while(running):
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try:
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for thermocouple in thermocouples:
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rj = thermocouple.get_rj()
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try:
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tc = thermocouple.get()
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except MAX31855Error as e:
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tc = "Error: "+ e.value
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running = False
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print("tc: {} and rj: {}".format(tc, rj))
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time.sleep(1)
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except KeyboardInterrupt:
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running = False
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for thermocouple in thermocouples:
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thermocouple.cleanup()
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