drivers: cst816s: optimize for power saving and responsiveness

Signed-off-by: Fuji Pebri <pebri86@gmail.com>
[daniel@redfelineinja.org.uk: removed leading underscore from method
arguments, removed redundant state tracking, adopt i2c.writeto_mem]
Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>

wasp/boards/pinetime/watch.py.in

@@ -81,7 +81,7 @@ try:
             Signal(Pin('USB_PWR', Pin.IN), invert=True))
     i2c = I2C(1, scl='I2C_SCL', sda='I2C_SDA')
     accel = BMA421(i2c)
-    touch = CST816S(i2c)
+    touch = CST816S(i2c, Pin('TP_INT', Pin.IN), Pin('TP_RST', Pin.OUT, value=0))
     vibrator = Vibrator(Pin('MOTOR', Pin.OUT, value=0), active_low=True)
 
     # Release flash from deep power-down

wasp/boards/simulator/watch.py

@@ -13,6 +13,7 @@ def print_exception(exc, file=sys.stdout):
 sys.print_exception = print_exception
 
 import draw565
+import array
 
 from machine import I2C
 from machine import Pin

wasp/drivers/cst816s.py

@@ -6,6 +6,8 @@
 """
 
 import array
+import time
+from machine import Pin
 
 class CST816S:
     """Hynitron CST816S I2C touch controller driver.
@@ -13,15 +15,44 @@ class CST816S:
     .. automethod:: __init__
     """
 
-    def __init__(self, bus):
+    def __init__(self, bus, intr, rst):
         """Specify the bus used by the touch controller.
 
         :param machine.I2C bus: I2C bus for the CST816S.
         """
         self.i2c = bus
+        self.tp_int = intr
+        self.tp_rst = rst
         self.dbuf = bytearray(6)
         self.event = array.array('H', (0, 0, 0))
 
+        self._reset()
+        self.tp_int.irq(trigger=Pin.IRQ_FALLING, handler=self.get_touch_data)
+
+    def _reset(self):
+        self.tp_rst.off()
+        time.sleep_ms(5)
+        self.tp_rst.on()
+        time.sleep_ms(50)
+
+    def get_touch_data(self, pin_obj):
+        """Receive a touch event by interrupt.
+
+        Check for a pending touch event and, if an event is pending,
+        prepare it ready to go in the event queue.
+        """
+        dbuf = self.dbuf
+        event = self.event
+
+        try:
+            self.i2c.readfrom_mem_into(21, 1, dbuf)
+        except OSError:
+            return None
+
+        event[0] = dbuf[0] # event
+        event[1] = ((dbuf[2] & 0xf) << 8) + dbuf[3] # x coord
+        event[2] = ((dbuf[4] & 0xf) << 8) + dbuf[5] # y coord
+
     def get_event(self):
         """Receive a touch event.
 
@@ -30,38 +61,32 @@ class CST816S:
 
         :return: An event record if an event is received, None otherwise.
         """
-        dbuf = self.dbuf
+        if self.event[0] == 0:
-        event = self.event
-
-        # TODO: check the interrupt pin
-
-        try:
-            self.i2c.readfrom_mem_into(21, 1, dbuf)
-        except OSError:
             return None
 
-        # Skip junk events
+        return self.event
-        if dbuf[0] == 0:
-            return None
 
-        x = ((dbuf[2] & 0xf) << 8) + dbuf[3]
+    def reset_touch_data(self):
-        y = ((dbuf[4] & 0xf) << 8) + dbuf[5]
+        """Reset touch data.
-        swipe_start = dbuf[2] & 0x80
 
-        # Skip identical events... when the I2C interface comes alive
+        Reset touch data, call this function after processing an event.
-        # we can still get back stale events
+        """
-        if dbuf[0] == event[0] and x == event[1] and y == event[2] \
+        self.event[0] = 0
-                and not swipe_start:
-            return None
 
-        # This is a good event, lets save it
+    def wake(self):
-        event[0] = dbuf[0]
+        """Wake up touch controller chip.
-        event[1] = x
-        event[2] = y
 
-        # Do not forward swipe start events
+        Just reset the chip in order to wake it up
-        if dbuf[2] & 0x80:
+        """
-            event[0] = 0
+        self._reset()
-            return None
 
-        return event
+    def sleep(self):
+        """Put touch controller chip on sleep mode to save power.
+        """
+        # Before we can sent the sleep command we have to reset the
+        # panel to get the I2C hardware running again...
+        self._reset()
+        self.i2c.writeto_mem(21, 0xa5, b'\x03')
+
+        # Ensure get_event() cannot return anything
+        self.event[0] = 0

wasp/wasp.py

@@ -232,6 +232,7 @@ class Manager():
             self.switch(self.quick_ring[0])
             self.app.sleep()
         watch.display.poweroff()
+        watch.touch.sleep()
         self._charging = watch.battery.charging()
         self.sleep_at = None
 
@@ -241,9 +242,7 @@ class Manager():
         watch.display.poweron()
         self.app.wake()
         watch.backlight.set(self._brightness)
-
+        watch.touch.wake()
-        # Discard any pending touch events
-        _ = watch.touch.get_event()
 
         self.keep_awake()
 
@@ -277,6 +276,7 @@ class Manager():
                 self.navigate(event[0])
         elif event[0] == 5 and self.event_mask & EventMask.TOUCH:
             self.app.touch(event)
+        watch.touch.reset_touch_data()
 
     def _tick(self):
         """Handle the system tick.