micropython/drivers: Move "onewire" bus driver from main repo.

Signed-off-by: Jim Mussared <jim.mussared@gmail.com>

micropython/drivers/bus/onewire/manifest.py

@@ -0,0 +1 @@
+module("onewire.py", opt=3)

micropython/drivers/bus/onewire/onewire.py

@@ -0,0 +1,92 @@
+# 1-Wire driver for MicroPython
+# MIT license; Copyright (c) 2016 Damien P. George
+
+import _onewire as _ow
+
+
+class OneWireError(Exception):
+    pass
+
+
+class OneWire:
+    SEARCH_ROM = 0xF0
+    MATCH_ROM = 0x55
+    SKIP_ROM = 0xCC
+
+    def __init__(self, pin):
+        self.pin = pin
+        self.pin.init(pin.OPEN_DRAIN, pin.PULL_UP)
+
+    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(self.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(self.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)