working but unlinted

Author: ladyada

adafruit_tfmini.py

@@ -39,7 +39,100 @@
 
 """
 
-# imports
+import time
+import struct
 
 __version__ = "0.0.0-auto.0"
 __repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_TFmini.git"
+
+_STARTCONFIG = b'\x42\x57\x02\x00\x00\x00\x01\x02'
+_STARTREPLY = b'\x57\x02\x01\x00\x00\x01\x02'  # minus header 0x42
+_CONFIGPARAM = b'\x42\x57\x02\x00'
+_ENDCONFIG = b'\x42\x57\x02\x00\x00\x00\x00\x02'
+_ENDREPLY = b'\x42\x57\x02\x01\x00\x00\x00\x02'
+
+MODE_SHORT = 2
+MODE_LONG = 7
+
+class TFmini:
+    """TF mini communication module, use with just RX or TX+RX for advanced
+    command & control.
+    """
+    
+    def __init__(self, uart, *, timeout=3):
+        self._uart = uart
+        self._uart.baudrate = 115200
+        self.timeout = timeout
+        self._strength = None
+        self._mode = None
+
+    @property
+    def distance(self):
+        """The most recent distance measurement in centimeters"""
+        # listen for new packet
+        stamp = time.monotonic()
+        while time.monotonic() - stamp < self.timeout:
+            # look for the header start
+            c = self._uart.read(1)
+            if c[0] != 0x59:
+                continue
+            # get remaining packet
+            data = self._uart.read(8)
+            # check first byte is magicbyte
+            framebyte, distance, self._strength, self._mode, _, checksum = struct.unpack("<BHHBBB",data)
+            # look for second 0x59 frame indicator
+            if framebyte != 0x59:
+                continue
+            # calculate and check sum
+            mysum = (sum(data[0:7]) + 0x59) & 0xFF
+            if mysum != checksum:
+                continue
+            return distance
+        raise RuntimeError("Timed out looking for valid data")
+
+    @property
+    def strength(self):
+        self.distance
+        return self._strength
+
+    @property
+    def mode(self):
+        self.distance
+        return self._mode
+
+    @mode.setter
+    def mode(self, newmode):
+        if not newmode in (MODE_LONG, MODE_SHORT):
+            raise ValueError("Invalid mode")
+        self._set_config(_CONFIGPARAM + bytes([0, 0, newmode, 0x11]))
+
+    def _set_config(self, command):
+        self._uart.write(_STARTCONFIG)
+        stamp = time.monotonic()
+        while (time.monotonic() - stamp) < self.timeout:
+            # look for the header start
+            c = self._uart.read(1)
+            if c is None or c[0] != 0x42:
+               continue
+            echo = self._uart.read(len(_STARTREPLY))
+            #print("start ", [hex(i) for i in echo])
+            if echo != _STARTREPLY:
+                raise RuntimeError("Did not receive config start echo")
+            break
+
+        # Finally, send the command
+        self._uart.write(command)
+        #print([hex(i) for i in command])
+        echo = self._uart.read(len(command))
+        cmdreply = bytearray(len(command))
+        cmdreply[:] = command
+        cmdreply[3] = 0x1
+        #print("cmd ", [hex(i) for i in echo])
+        if echo != cmdreply:
+            raise RuntimeError("Did not receive config command echo")
+
+        self._uart.write(_ENDCONFIG)
+        echo = self._uart.read(len(_ENDREPLY))
+        #print("end ", [hex(i) for i in echo])
+        if echo != _ENDREPLY:
+            raise RuntimeError("Did not receive config end echo")