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Dec 30, 2021
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Eliminate race condition to improve coordinate accuracy and reliability. #18

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768d10c
Eliminate race condition between x/y values and z (press) values.
CedarGroveStudios Dec 29, 2021
bc3cd0f
Eliminate race condition
CedarGroveStudios Dec 29, 2021
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65 changes: 33 additions & 32 deletions adafruit_touchscreen.py
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Original file line number Diff line number Diff line change
Expand Up @@ -62,8 +62,8 @@ class Touchscreen:
:attr:`calibration` is a tuple of two tuples, the default is
((0, 65535), (0, 65535)). The numbers are the min/max readings for the
X and Y coordinate planes, respectively. To figure these out, pass in
no calibration value and read the raw values out while touching the
panel.
no calibration value or size value and read the raw minimum and maximum
values out while touching the panel.
:attr:`size` is a tuple that gives the X and Y pixel size of the underlying
screen. If passed in, we will automatically scale/rotate so touches
correspond to the graphical coordinate system.
Expand Down Expand Up @@ -108,6 +108,7 @@ def __init__(
self._rx_plate = x_resistance
self._xsamples = [0] * samples
self._ysamples = [0] * samples
self._zsamples = [0] * samples
if not calibration:
calibration = ((0, 65535), (0, 65535))
self._calib = calibration
Expand All @@ -118,36 +119,6 @@ def __init__(
def touch_point(self): # pylint: disable=too-many-locals
"""A tuple that represents the x, y and z (touch pressure) coordinates
of a touch. Or, None if no touch is detected"""
with DigitalInOut(self._yp_pin) as y_p:
with DigitalInOut(self._ym_pin) as y_m:
with AnalogIn(self._xp_pin) as x_p:
y_p.switch_to_output(True)
y_m.switch_to_output(False)
for i in range( # pylint: disable=consider-using-enumerate
len(self._xsamples)
):
self._xsamples[i] = x_p.value
x = sum(self._xsamples) / len(self._xsamples)
x_size = 65535
if self._size:
x_size = self._size[0]
x = int(map_range(x, self._calib[0][0], self._calib[0][1], 0, x_size))

with DigitalInOut(self._xp_pin) as x_p:
with DigitalInOut(self._xm_pin) as x_m:
with AnalogIn(self._yp_pin) as y_p:
x_p.switch_to_output(True)
x_m.switch_to_output(False)
for i in range( # pylint: disable=consider-using-enumerate
len(self._ysamples)
):
self._ysamples[i] = y_p.value
y = sum(self._ysamples) / len(self._ysamples)
y_size = 65535
if self._size:
y_size = self._size[1]
y = int(map_range(y, self._calib[1][0], self._calib[1][1], 0, y_size))

z_1 = z_2 = z = None
with DigitalInOut(self._xp_pin) as x_p:
x_p.switch_to_output(False)
Expand All @@ -160,5 +131,35 @@ def touch_point(self): # pylint: disable=too-many-locals
# print(z_1, z_2)
z = 65535 - (z_2 - z_1)
if z > self._zthresh:
with DigitalInOut(self._yp_pin) as y_p:
with DigitalInOut(self._ym_pin) as y_m:
with AnalogIn(self._xp_pin) as x_p:
y_p.switch_to_output(True)
y_m.switch_to_output(False)
for i in range( # pylint: disable=consider-using-enumerate
len(self._xsamples)
):
self._xsamples[i] = x_p.value
x = sum(self._xsamples) / len(self._xsamples)
x_size = 65535
if self._size:
x_size = self._size[0]
x = int(map_range(x, self._calib[0][0], self._calib[0][1], 0, x_size))

with DigitalInOut(self._xp_pin) as x_p:
with DigitalInOut(self._xm_pin) as x_m:
with AnalogIn(self._yp_pin) as y_p:
x_p.switch_to_output(True)
x_m.switch_to_output(False)
for i in range( # pylint: disable=consider-using-enumerate
len(self._ysamples)
):
self._ysamples[i] = y_p.value
y = sum(self._ysamples) / len(self._ysamples)
y_size = 65535
if self._size:
y_size = self._size[1]
y = int(map_range(y, self._calib[1][0], self._calib[1][1], 0, y_size))

return (x, y, z)
return None