Low power mode management by the STM8TL5x STMTouch Library

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Doc ID 018847 Rev 3

7

Low power mode management by the STM8TL5x

STMTouch Library

7.1

Configuration available in the stm8_tsl_conf.h file

This section presents the parameters of the library, corresponding to the features presented

in Section 6: ProxSense and low power modes.

7.1.1

Acquisition time

The acquisition time depends on the:

1.

Frequency of the acquisition

2.

Up and pass length

3.

Average value targeted when there is no touch

Frequency of the acquisition

The frequency of the acquisition is set in the TSLPRM_PXS_HSI (the high-speed internal

clock that is dedicated to the analog ProxSense system). The possible frequencies are:

●

16 MHz (TSLPRM_PXS_HSI 16000)

●

8 MHz (TSLPRM_PXS_HSI 8000)

●

4 MHz (TSLPRM_PXS_HSI 4000)

●

2 MHz (TSLPRM_PXS_HSI 2000)

●

1 MHz (TSLPRM_PXS_HSI 1000)

●

500 kHz (TSLPRM_PXS_HSI 500)

●

250 kHz (TSLPRM_PXS_HSI 250)

●

125 kHz (TSLPRM_PXS_HSI 125)

Up and pass length

Up and Pass are the two active phases of a ProxSense acquisition cycle. Their length must

be selected in order to ensure a correct charge and discharge of the projected capacitance

between each receiver/transmitter pair.

If the Up and Pass lengths are set for a value of less than five by

TSLPRM_PXS_UP_LENGTH and TSLPRM_PXS_PASS_LENGTH definitions, each phase

lasts this value (TSLPRM_PXS_UP_LENGTH/ TSLPRM_PXS_PASS_LENGTH) + 0.5

cycles. For a value greater than or equal to five, each Up and Pass length is

2^(TSLPRM_PXS_UP_LENGTH-2)+0.5 cycles and 2^(TSLPRM_PXS_PASS_LENGTH-

2)+0.5 cycles.

If the TSLPRM_PXS_UP_LENGTH and TSLPRM_PXS_PASS_LENGTH are equal, Table 4

gives the correspondence between the Up and Pass length value and the number of cycles

of a complete phase (Up + Pass + deadtimes).