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import time
import pyb
import _onewire as _ow
class OneWire:
CMD_SEARCHROM = const(0xf0)
CMD_READROM = const(0x33)
CMD_MATCHROM = const(0x55)
CMD_SKIPROM = const(0xcc)
def __init__(self, pin):
self.pin = pin
self.pin.init(pin.OPEN_DRAIN, pin.PULL_NONE)
def reset(self):
return _ow.reset(self.pin)
def read_bit(self):
return _ow.readbit(self.pin)
def read_byte(self):
return _ow.readbyte(self.pin)
def read_bytes(self, count):
buf = bytearray(count)
for i in range(count):
buf[i] = _ow.readbyte(self.pin)
return buf
def write_bit(self, value):
return _ow.writebit(self.pin, value)
def write_byte(self, value):
return _ow.writebyte(self.pin, value)
def write_bytes(self, buf):
for b in buf:
_ow.writebyte(self.pin, b)
def select_rom(self, rom):
self.reset()
self.write_byte(CMD_MATCHROM)
self.write_bytes(rom)
def scan(self):
devices = []
diff = 65
rom = False
for i in range(0xff):
rom, diff = self._search_rom(rom, diff)
if rom:
devices += [rom]
if diff == 0:
break
return devices
def _search_rom(self, l_rom, diff):
if not self.reset():
return None, 0
self.write_byte(CMD_SEARCHROM)
if not l_rom:
l_rom = bytearray(8)
rom = bytearray(8)
next_diff = 0
i = 64
for byte in range(8):
r_b = 0
for bit in range(8):
b = self.read_bit()
if self.read_bit():
if b: # there are no devices or there is an error on the bus
return None, 0
else:
if not b: # collision, two devices with different bit meaning
if diff > i or ((l_rom[byte] & (1 << bit)) and diff != i):
b = 1
next_diff = i
self.write_bit(b)
if b:
r_b |= 1 << bit
i -= 1
rom[byte] = r_b
return rom, next_diff
def crc8(self, data):
return _ow.crc8(data)
class DS18B20:
THERM_CMD_CONVERTTEMP = const(0x44)
THERM_CMD_RSCRATCHPAD = const(0xbe)
def __init__(self, onewire):
self.ow = onewire
self.roms = []
def scan(self):
self.roms = []
for rom in self.ow.scan():
if rom[0] == 0x28:
self.roms += [rom]
return self.roms
def start_measure(self):
if not self.ow.reset():
return False
self.ow.write_byte(CMD_SKIPROM)
self.ow.write_byte(THERM_CMD_CONVERTTEMP)
return True
def get_temp(self, rom):
if not self.ow.reset():
return None
self.ow.select_rom(rom)
self.ow.write_byte(THERM_CMD_RSCRATCHPAD)
buf = self.ow.read_bytes(9)
if self.ow.crc8(buf):
return None
return self._convert_temp(buf)
def _convert_temp(self, data):
temp_lsb = data[0]
temp_msb = data[1]
return (temp_msb << 8 | temp_lsb) / 16
# connect 1-wire temp sensors to GPIO12 for this test
def test():
dat = pyb.Pin(12)
ow = OneWire(dat)
ds = DS18B20(ow)
roms = ow.scan()
print('found devices:', roms)
for i in range(4):
print('temperatures:', end=' ')
ds.start_measure()
time.sleep_ms(750)
for rom in roms:
print(ds.get_temp(rom), end=' ')
print()
#pyb.freq(80000000)
#pyb.freq(160000000)
test()
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