kopia lustrzana https://github.com/botheredbybees/kilnController
126 wiersze
4.0 KiB
Python
126 wiersze
4.0 KiB
Python
#!/usr/bin/python
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import RPi.GPIO as GPIO
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import time
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class MAX6675(object):
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'''Python driver for [MAX6675 Cold-Junction Compensated Thermocouple-to-Digital Converter](http://www.adafruit.com/datasheets/MAX6675.pdf)
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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 read(self):
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'''Reads 16 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 16 bits
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for i in range(16):
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GPIO.output(self.clock_pin, GPIO.LOW)
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time.sleep(0.001)
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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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time.sleep(0.001)
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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_16 = None):
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'''Checks errors on bit D2'''
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if data_16 is None:
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data_16 = self.data
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noConnection = (data_16 & 0x4) != 0 # tc input bit, D2
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if noConnection:
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raise MAX6675Error("No Connection") # open thermocouple
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def data_to_tc_temperature(self, data_16 = None):
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'''Takes an integer and returns a thermocouple temperature in celsius.'''
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if data_16 is None:
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data_16 = self.data
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# Remove bits D0-3
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tc_data = ((data_16 >> 3) & 0xFFF)
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# 12-bit resolution
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return (tc_data * 0.25)
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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 MAX6675Error(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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# default example
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cs_pin = 24
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clock_pin = 23
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data_pin = 22
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units = "c"
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thermocouple = MAX6675(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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try:
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tc = thermocouple.get()
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except MAX6675Error as e:
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tc = "Error: "+ e.value
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running = False
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print("tc: {}".format(tc))
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time.sleep(1)
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except KeyboardInterrupt:
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running = False
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thermocouple.cleanup()
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