STM32F042C4 datasheet(20/117 Pages) STMICROELECTRONICS

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Functional overview

STM32F042x4 STM32F042x6

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DocID025832 Rev 5

3.10.3

VBAT battery voltage monitoring

This embedded hardware feature allows the application to measure the VBAT battery voltage

using the internal ADC channel ADC_IN18. As the VBAT voltage may be higher than VDDA,

and thus outside the ADC input range, the VBAT pin is internally connected to a bridge

divider by 2. As a consequence, the converted digital value is half the VBAT voltage.

3.11

Touch sensing controller (TSC)

The STM32F042x4/x6 devices provide a simple solution for adding capacitive sensing

functionality to any application. These devices offer up to 14 capacitive sensing channels

distributed over 5 analog I/O groups.

Capacitive sensing technology is able to detect the presence of a finger near a sensor which

is protected from direct touch by a dielectric (glass, plastic...). The capacitive variation

introduced by the finger (or any conductive object) is measured using a proven

implementation based on a surface charge transfer acquisition principle. It consists in

charging the sensor capacitance and then transferring a part of the accumulated charges

into a sampling capacitor until the voltage across this capacitor has reached a specific

threshold. To limit the CPU bandwidth usage, this acquisition is directly managed by the

hardware touch sensing controller and only requires few external components to operate.

For operation, one capacitive sensing GPIO in each group is connected to an external

capacitor and cannot be used as effective touch sensing channel.

The touch sensing controller is fully supported by the STMTouch touch sensing firmware

library, which is free to use and allows touch sensing functionality to be implemented reliably

in the end application.

Table 5. Capacitive sensing GPIOs available on STM32F042x4/x6 devices

Group

Capacitive sensing

signal name

name

Group

Capacitive sensing

signal name

name

TSC_G1_IO1

PA0

TSC_G4_IO1

PA9

TSC_G1_IO2

PA1

TSC_G4_IO2

PA10

TSC_G1_IO3

PA2

TSC_G4_IO3

PA11

TSC_G1_IO4

PA3

TSC_G4_IO4

PA12

TSC_G2_IO1

PA4

TSC_G5_IO1

PB3

TSC_G2_IO2

PA5

TSC_G5_IO2

PB4

TSC_G2_IO3

PA6

TSC_G5_IO3

PB6

TSC_G2_IO4

PA7

TSC_G5_IO4

PB7

TSC_G3_IO2

PB0

TSC_G3_IO3

PB1

TSC_G3_IO4

PB2

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