STM8-TOUCH-LIB STMicroelectronics, STM8-TOUCH-LIB Datasheet - Page 2

• Manufacturer Part Number: STM8-TOUCH-LIB
• Description: STM8 touch sensing library
• Manufacturer: STMicroelectronics

Specifications of STM8-TOUCH-LIB

• Rc Acquisition: up to 24 keys and 2 wheels/sliders supported
• Ct Acquisition: up to 16 keys and 2 wheels/sliders supported

Resistor-capacitor (RC) acquisition principle
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Resistor-capacitor (RC) acquisition principle
The RC acquisition principle consists in measuring the charge and discharge time duration
of a RC cell made of the electrode capacitance (C
The RC acquisition is supported by all STM8S and STM8L microcontrollers and requires a
direct connection of the device to earth to operate properly.
The main features are the following:
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●
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Charge transfer (CT) acquisition principle
The charge transfer acquisition consists in charging the electrode capacitance (C
transferring part of the accumulated charge into a sampling capacitor (C
repeated until the voltage across C
required to reach the threshold depends on the size of the electrode capacitance. This
acquisition principle provides a better sensitivity and robustness than RC acquisition.
It requires a dedicated hardware composed of analog switches and STM8L MCU.
The charge transfer acquisition is only supported by STM8L101x and STM8L15x devices
since it requires a dedicated hardware composed of analog switches used to interconnect
several GPIOs which is only available on these products.
The main features are the following:
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Up to 24 touchkeys distributed over 3 GPIO ports
Up to 2 wheels or sliders with 2 different hardware implementations (5 or 8 capacitive
sensing channels)
Capacitive sensing channels are acquired sequentially
Number touchkeys supported
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–
Up to 2 wheels or sliders with a single hardware implementation (3 capacitive sensing
channels)
Number of capacitive sensing channels acquired simultaneously
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Up to 6 touchkeys on STM8L101x MCUs
Up to 16 touchkeys on STM8L15x MCUs
Up to 2 channels on STM8L101x MCUs
Up to 8 channels on STM8L15x MCUs
Doc ID 17896 Rev 1
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reaches a given threshold. The number of transfers
X
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S
STM8-TOUCH-LIB
). This sequence is
L
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