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docs,esp32: Update machine.TouchPad docs for ESP32-S2 and ESP32-S3.

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Signed-off-by: Angus Gratton <angus@redyak.com.au>
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Angus Gratton
2024-11-06 18:06:48 +11:00
committed by Angus Gratton
parent 66e699e8a5
commit 154d141965
1 changed files with 20 additions and 7 deletions
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docs/esp32/quickref.rst
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@@ -751,20 +751,33 @@ APA102 (DotStar) uses a different driver as it has an additional clock pin.
Capacitive touch
----------------
Use the ``TouchPad`` class in the ``machine`` module::
ESP32, ESP32-S2 and ESP32-S3 support capacitive touch via the ``TouchPad`` class
in the ``machine`` module::
from machine import TouchPad, Pin
t = TouchPad(Pin(14))
t.read() # Returns a smaller number when touched
``TouchPad.read`` returns a value relative to the capacitive variation. Small numbers (typically in
the *tens*) are common when a pin is touched, larger numbers (above *one thousand*) when
no touch is present. However the values are *relative* and can vary depending on the board
and surrounding composition so some calibration may be required.
``TouchPad.read`` returns a value proportional to the capacitance between the
pin and the board's Ground connection. On ESP32 the number becomes smaller when
the pin (or connected touch pad) is touched, on ESP32-S2 and ESP32-S3 the number
becomes larger when the pin is touched.
There are ten capacitive touch-enabled pins that can be used on the ESP32: 0, 2, 4, 12, 13
14, 15, 27, 32, 33. Trying to assign to any other pins will result in a ``ValueError``.
In all cases, a touch causes a significant change in the return value. Note the
returned values are *relative* and can vary depending on the board and
surrounding environment so some calibration (i.e. comparison to a baseline or
rolling average) may be required.
========= ==============================================
Chip Touch-enabled pins
--------- ----------------------------------------------
ESP32 0, 2, 4, 12, 13, 14, 15, 27, 32, 33
ESP32-S2 1 to 14 inclusive
ESP32-S3 1 to 14 inclusive
========= ==============================================
Trying to assign to any other pins will result in a ``ValueError``.
Note that TouchPads can be used to wake an ESP32 from sleep::