RM0367 Rev 7 415/1043
RM0367 Touch sensing controller (TSC)
432
18.3 TSC functional description
18.3.1 TSC block diagram
The block diagram of the touch sensing controller is shown in Figure 79.
Figure 79. TSC block diagram
18.3.2 Surface charge transfer acquisition overview
The surface charge transfer acquisition is a proven, robust and efficient way to measure a
capacitance. It uses a minimum number of external components to operate with a single
ended electrode type. This acquisition is designed around an analog I/O group composed of
up to four GPIOs (see Figure 80). Several analog I/O groups are available to allow the
acquisition of several capacitive sensing channels simultaneously and to support a larger
number of capacitive sensing channels. Within a same analog I/O group, the acquisition of
the capacitive sensing channels is sequential.
One of the GPIOs is dedicated to the sampling capacitor C
S
. Only one sampling capacitor
I/O per analog I/O group must be enabled at a time.
The remaining GPIOs are dedicated to the electrodes and are commonly called channels.
For some specific needs (such as proximity detection), it is possible to simultaneously
enable more than one channel per analog I/O group.
I/O control
logic
SYNC
Pulse generator
Spread spectrum
TSC_IOG1CR
TSC_IOG2CR
TSC_IOGxCR
f
HCLK
Clock
prescalers
Group counters
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