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# SPDX-License-Identifier: LGPL-3.0-or-later
# Copyright (C) 2020 Daniel Thompson
"""Hynitron CST816S touch contoller driver
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"""
import array
class CST816S:
"""Hynitron CST816S I2C touch controller driver.
.. automethod:: __init__
"""
def __init__(self, bus):
"""Specify the bus used by the touch controller.
:param machine.I2C bus: I2C bus for the CST816S.
"""
self.i2c = bus
self.dbuf = bytearray(6)
self.event = array.array('H', (0, 0, 0))
def get_event(self):
"""Receive a touch event.
Check for a pending touch event and, if an event is pending,
prepare it ready to go in the event queue.
:return: An event record if an event is received, None otherwise.
"""
dbuf = self.dbuf
event = self.event
# TODO: check the interrupt pin
try:
self.i2c.readfrom_mem_into(21, 1, dbuf)
except OSError:
return None
# Skip junk events
if dbuf[0] == 0:
return None
x = ((dbuf[2] & 0xf) << 8) + dbuf[3]
y = ((dbuf[4] & 0xf) << 8) + dbuf[5]
swipe_start = dbuf[2] & 0x80
# Skip identical events... when the I2C interface comes alive
# we can still get back stale events
if dbuf[0] == event[0] and x == event[1] and y == event[2] \
and not swipe_start:
return None
# This is a good event, lets save it
event[0] = dbuf[0]
event[1] = x
event[2] = y
# Do not forward swipe start events
if dbuf[2] & 0x80:
event[0] = 0
return None
return event
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