Limitations; Operating Voltage; Touch Sensing Slider; Table 23. Touch Sensing Related Solder Bridges - ST STM32L073Z-EVAL User Manual

Hardware layout and configuration
A 1st order low pass with 3 Hz cut-off frequency, is composed of 47 K resistors combined
with 1 uF capacitors to feedback the first amplifiers U3A and U3B.
7.21.5

Limitations

No exclusivity.
7.21.6

Operating voltage

Operating voltage is fixed at: +3.3 V
7.22

Touch sensing slider

The STM32L073Z-EVAL evaluation board supports a touch sensing slider based on either
RC charging or charge transfer technology. The charge transfer technology is enabled by
the default assembly.
The touch sensing slider is connected to PB12, PB0, PA1 and the related charge capacitors
are respectively connected to PB13, PB1 and PA2. PC6 and PC7 manage an active shield
reducing sensitivity to other signals. The active shield is placed on the internal layer 2,
immediately under the slider to eliminate influence from other circuits.
Some rework on solder bridges and resistors is necessary to use touch sensing and it is
described in the below
Solder
bridges
SB6
SB5
SB8
SB14
SB11
SB12
SB17
SB18
SB24
SB22
SB15
SB16
SB7
SB13
38/64
Table 23:

Table 23. Touch sensing related solder bridges

Settings to
enable STM32
touch port
sensing
Close PB12
Open PB12
Close PB0
Open PB0
Close PA1
Open PA1
Close PC6
Open PC6
Close PC7
Open PC7
Close PB13
Open PB13
Close PB1
Open PB1
Connects the 1st touch sensing zone to PB12.
Disconnects PB12 from track to LCD glass to avoid disturbances.
Connects the 2nd touch sensing zone to PB0.
Disconnects PB0 from track to LCD glass to avoid disturbances.
Connects the 3rd touch sensing zone to PA1.
Disconnects PA1 from track to LCD glass to avoid disturbances.
Connects the shield to PC6.
Disconnects PC6 from track to LCD glass to avoid disturbances.
Connects the charge capacitor of shield to PC7.
Disconnects PC7 from track to LCD glass to avoid disturbances.
Connects the charge capacitor to PB13.
Disconnects PB13 from track to LCD glass to avoid disturbances.
Connects the charge capacitor to PB1.
Disconnects PB1 from track to LCD glass to avoid disturbances.
UM1878 Rev 2
Description
UM1878