reimplement wakeup

Author: caternuson

adafruit_atecc/adafruit_atecc.py

@@ -129,48 +129,29 @@ def __init__(self, i2c_bus, address=_REG_ATECC_DEVICE_ADDR, debug=False):
         """
         self._debug = debug
         self._i2cbuf = bytearray(12)
-        self._i2c_bus = i2c_bus
-        self._i2c_device = None
-        self.wakeup()
-        if not self._i2c_device:
-            self._i2c_device = I2CDevice(self._i2c_bus, address)
-        self.idle()
+        # don't probe, the device will NACK until woken up
+        self._wake_device = I2CDevice(i2c_bus, 0x00, probe=False)
+        self._i2c_device = I2CDevice(i2c_bus, address, probe=False)
         if (self.version() >> 8) not in (_ATECC_508_VER, _ATECC_608_VER):
             raise RuntimeError(
                 "Failed to find 608 or 508 chip. Please check your wiring."
             )
 
     def wakeup(self):
         """Wakes up THE ATECC608A from sleep or idle modes.
-        Returns True if device woke up from sleep/idle mode.
         """
-        while not self._i2c_bus.try_lock():
-            pass
-        # check if it exists, first
-        if 0x60 in self._i2c_bus.scan():
-            self._i2c_bus.unlock()
-            return
-        zero_bits = bytearray(2)
+        # This is a hack to generate the ATECC Wake condition, which is SDA
+        # held low for t > 60us (twlo). For an I2C clock freq of 100kHz, 8
+        # clock cycles will be 80us. This signal is generated by trying to
+        # address something at 0x00. It will fail, but the pattern should
+        # wake up the ATECC.
+        # pylint: disable=bare-except
         try:
-            self._i2c_bus.writeto(0x0, zero_bits)
-        except OSError:
-            pass  # this may fail, that's ok - its just to wake up the chip!
-        time.sleep(_TWLO_TIME)
-        data = self._i2c_bus.scan()  # check for an i2c device
-
-        try:
-            if data[0] != 96:
-                raise TypeError("ATECCx08 not found - please check your wiring!")
-        except IndexError:
-            raise IndexError("ATECCx08 not found - please check your wiring!")
-        self._i2c_bus.unlock()
-        if not self._i2c_device:
-            self._i2c_device = I2CDevice(self._i2c_bus, _REG_ATECC_DEVICE_ADDR)
-        # check if we are ready to read from
-        r = bytearray(1)
-        self._get_response(r)
-        if r[0] != 0x11:
-            raise RuntimeError("Failed to wakeup")
+            with self._wake_device as i2c:
+                i2c.write(bytes([0x00]))
+        except:
+            pass
+        time.sleep(0.001)
 
     def idle(self):
         """Puts the chip into idle mode