102 lines
3.1 KiB
Python
102 lines
3.1 KiB
Python
"""
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DS18x20 temperature sensor driver for MicroPython.
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This driver uses the OneWire driver to control DS18S20 and DS18B20
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temperature sensors. It supports multiple devices on the same 1-wire bus.
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The following example assumes the ground of your DS18x20 is connected to
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Y11, vcc is connected to Y9 and the data pin is connected to Y10.
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>>> from machine import Pin
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>>> gnd = Pin('Y11', Pin.OUT_PP)
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>>> gnd.off()
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>>> vcc = Pin('Y9', Pin.OUT_PP)
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>>> vcc.on()
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>>> from ds18x20 import DS18X20
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>>> d = DS18X20(Pin('Y10'))
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Call read_temps to read all sensors:
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>>> result = d.read_temps()
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>>> print(result)
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[20.875, 20.8125]
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Call read_temp to read the temperature of a specific sensor:
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>>> result = d.read_temp(d.roms[0])
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>>> print(result)
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20.25
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If only one DS18x20 is attached to the bus, then you don't need to
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pass a ROM to read_temp:
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>>> result = d.read_temp()
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>>> print(result)
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20.25
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"""
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from onewire import OneWire
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class DS18X20(object):
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def __init__(self, pin):
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self.ow = OneWire(pin)
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# Scan the 1-wire devices, but only keep those which have the
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# correct # first byte in their rom for a DS18x20 device.
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self.roms = [rom for rom in self.ow.scan() if rom[0] == 0x10 or rom[0] == 0x28]
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def read_temp(self, rom=None):
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"""
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Read and return the temperature of one DS18x20 device.
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Pass the 8-byte bytes object with the ROM of the specific device you want to read.
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If only one DS18x20 device is attached to the bus you may omit the rom parameter.
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"""
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rom = rom or self.roms[0]
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ow = self.ow
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ow.reset()
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ow.select_rom(rom)
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ow.write_byte(0x44) # Convert Temp
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while True:
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if ow.read_bit():
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break
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ow.reset()
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ow.select_rom(rom)
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ow.write_byte(0xbe) # Read scratch
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data = ow.read_bytes(9)
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return self.convert_temp(rom[0], data)
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def read_temps(self):
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"""
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Read and return the temperatures of all attached DS18x20 devices.
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"""
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temps = []
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for rom in self.roms:
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temps.append(self.read_temp(rom))
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return temps
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def convert_temp(self, rom0, data):
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"""
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Convert the raw temperature data into degrees celsius and return as a float.
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"""
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temp_lsb = data[0]
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temp_msb = data[1]
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if rom0 == 0x10:
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if temp_msb != 0:
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# convert negative number
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temp_read = temp_lsb >> 1 | 0x80 # truncate bit 0 by shifting, fill high bit with 1.
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temp_read = -((~temp_read + 1) & 0xff) # now convert from two's complement
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else:
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temp_read = temp_lsb >> 1 # truncate bit 0 by shifting
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count_remain = data[6]
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count_per_c = data[7]
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temp = temp_read - 0.25 + (count_per_c - count_remain) / count_per_c
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return temp
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elif rom0 == 0x28:
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temp = (temp_msb << 8 | temp_lsb) / 16
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if (temp_msb & 0xf8) == 0xf8: # for negative temperature
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temp -= 0x1000
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return temp
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else:
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assert False
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