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drivers/onewire: Move onewire.py, ds18x20.py from esp8266 to drivers.

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These drivers can now be used by any port (so long as that port has the
_onewire driver from extmod/modonewire.c).

These drivers replace the existing 1-wire and DS18X20 drivers in the
drivers/onewire directory.  The existing ones were pyboard-specific and
not very efficient nor minimal (although the 1-wire driver was written in
pure Python it only worked at large enough CPU frequency).

This commit brings backwards incompatible API changes to the existing
1-wire drivers.  User code should be converted to use the new drivers, or
check out the old version of the code and keep a local copy (it should
continue to work unchanged).
This commit is contained in:
Damien George
2017-06-22 16:28:07 +10:00
parent b19138e82e
commit a065d78675
4 changed files with 111 additions and 548 deletions
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51
esp8266/modules/ds18x20.py
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@@ -1,51 +0,0 @@
# DS18x20 temperature sensor driver for MicroPython.
# MIT license; Copyright (c) 2016 Damien P. George
from micropython import const
_CONVERT = const(0x44)
_RD_SCRATCH = const(0xbe)
_WR_SCRATCH = const(0x4e)
class DS18X20:
def __init__(self, onewire):
self.ow = onewire
self.buf = bytearray(9)
def scan(self):
return [rom for rom in self.ow.scan() if rom[0] == 0x10 or rom[0] == 0x28]
def convert_temp(self):
self.ow.reset(True)
self.ow.writebyte(self.ow.SKIP_ROM)
self.ow.writebyte(_CONVERT)
def read_scratch(self, rom):
self.ow.reset(True)
self.ow.select_rom(rom)
self.ow.writebyte(_RD_SCRATCH)
self.ow.readinto(self.buf)
if self.ow.crc8(self.buf):
raise Exception('CRC error')
return self.buf
def write_scratch(self, rom, buf):
self.ow.reset(True)
self.ow.select_rom(rom)
self.ow.writebyte(_WR_SCRATCH)
self.ow.write(buf)
def read_temp(self, rom):
buf = self.read_scratch(rom)
if rom[0] == 0x10:
if buf[1]:
t = buf[0] >> 1 | 0x80
t = -((~t + 1) & 0xff)
else:
t = buf[0] >> 1
return t - 0.25 + (buf[7] - buf[6]) / buf[7]
else:
t = buf[1] << 8 | buf[0]
if t & 0x8000: # sign bit set
t = -((t ^ 0xffff) + 1)
return t / 16

91
esp8266/modules/onewire.py
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@@ -1,91 +0,0 @@
# 1-Wire driver for MicroPython on ESP8266
# MIT license; Copyright (c) 2016 Damien P. George
from micropython import const
import _onewire as _ow
class OneWireError(Exception):
pass
class OneWire:
SEARCH_ROM = const(0xf0)
MATCH_ROM = const(0x55)
SKIP_ROM = const(0xcc)
def __init__(self, pin):
self.pin = pin
self.pin.init(pin.OPEN_DRAIN)
def reset(self, required=False):
reset = _ow.reset(self.pin)
if required and not reset:
raise OneWireError
return reset
def readbit(self):
return _ow.readbit(self.pin)
def readbyte(self):
return _ow.readbyte(self.pin)
def readinto(self, buf):
for i in range(len(buf)):
buf[i] = _ow.readbyte(self.pin)
def writebit(self, value):
return _ow.writebit(self.pin, value)
def writebyte(self, value):
return _ow.writebyte(self.pin, value)
def write(self, buf):
for b in buf:
_ow.writebyte(self.pin, b)
def select_rom(self, rom):
self.reset()
self.writebyte(MATCH_ROM)
self.write(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.writebyte(SEARCH_ROM)
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.readbit()
if self.readbit():
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.writebit(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)