esp8266: Add tests/onewire.py as a driver and test code for ds18b20 dev.

esp8266/tests/onewire.py

+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()