micropython/drivers: Move "dx18x20" sensor driver from main repo.

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

micropython/drivers/sensor/ds18x20/ds18x20.py

@@ -0,0 +1,52 @@
+# 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] in (0x10, 0x22, 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

micropython/drivers/sensor/ds18x20/manifest.py

@@ -0,0 +1,2 @@
+require("onewire")
+module("ds18x20.py", opt=3)