ST STM32L0x3 User Manual

Touch sensing controller (TSC) RM0367
418/1043 RM0367 Rev 7
The Reset and Clock Controller (RCC) provides dedicated bits to enable the touch sensing
controller clock and to reset this peripheral. For more information, refer to Section 7: Reset
and clock control (RCC).
18.3.4 Charge transfer acquisition sequence
An example of a charge transfer acquisition sequence is detailed in Figure 82.
Figure 82. Charge transfer acquisition sequence
For higher flexibility, the charge transfer frequency is fully configurable. Both the pulse high
state (charge of C
X
) and the pulse low state (transfer of charge from C
X
to C
S
) duration can
be defined using the CTPH[3:0] and CTPL[3:0] bits in the TSC_CR register. The standard
range for the pulse high and low states duration is 500 ns to 2 µs. To ensure a correct
measurement of the electrode capacitance, the pulse high state duration must be set to
ensure that C
X
is always fully charged.
A dead time where both the sampling capacitor I/O and the channel I/O are in input floating
state is inserted between the pulse high and low states to ensure an optimum charge
transfer acquisition sequence. This state duration is 2 periods of HCLK.
At the end of the pulse high state and if the spread spectrum feature is enabled, a variable
number of periods of the SSCLK clock are added.
The reading of the sampling capacitor I/O, to determine if the voltage across C
S
has
reached the given threshold, is performed at the end of the pulse low state.
Note: The following TSC control register configurations are forbidden:
• bits PGPSC are set to ‘000’ and bits CTPL are set to ‘0000’
• bits PGPSC are set to ‘000’ and bits CTPL are set to ‘0001’
• bits PGPSC are set to ‘001’ and bits CTPL are set to ‘0000’
MSv30932V3
CLK_AHB
C
X
1
0
HiZ
C
S
1
0
HiZ
State
Dead time state
Discharge
C
X
and C
S
Pulse high
state
(charge of C
X
)
Dead time state Dead time state Dead time state Dead time state
C
S
reading
Spread spectrum state
C
S
reading
Pulse low
state (charge
transfer from
C
X
to C
S
)
Charge transfer frequency
t
Pulse high
state
Pulse low
state

ST STM32L0x3 Specifications

General

Brand	ST
Model	STM32L0x3
Category	Microcontrollers
Language	English